diff --git a/.github/workflows/test_cxx_backend.yml b/.github/workflows/test_cxx_backend.yml
index bfcdc854..87d22afd 100644
--- a/.github/workflows/test_cxx_backend.yml
+++ b/.github/workflows/test_cxx_backend.yml
@@ -35,6 +35,10 @@ jobs:
       - name: Build and test capi_test against backend
         working-directory: capi_test
         run: ./test_with_cxx_backend.sh
+      
+      - name: Build and run capi_sample
+        working-directory: capi_sample
+        run: ./run_sample.sh
 
   test-cxx-backend-rollup:
     runs-on: ubuntu-latest
diff --git a/.gitignore b/.gitignore
index 03291f14..bc2630f0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -34,6 +34,9 @@
 # CMake
 build
 work_cxx
+work_cxx_blas
+work_cxx_wo_blas
+capi_benchmark/work_cxx_blas/
 
 .DS_Store
 .vscode/settings.json
diff --git a/README.md.bak b/README.md.bak
deleted file mode 100644
index 908c2e96..00000000
--- a/README.md.bak
+++ /dev/null
@@ -1,502 +0,0 @@
-# libsparseir
-
-[![CMake on a single platform](https://github.com/SpM-lab/libsparseir/actions/workflows/CI_cmake.yml/badge.svg)](https://github.com/SpM-lab/libsparseir/actions/workflows/CI_cmake.yml)
-
-> [!WARNING]
-> This C++ project is still under construction. Please use other repositories:
-> - https://github.com/SpM-lab/sparse-ir
-> - https://github.com/SpM-lab/SparseIR.jl
-> - https://github.com/SpM-lab/sparse-ir-fortran
-
-## Description
-
-This C++ library provides routines for constructing and working with the intermediate representation of correlation functions. It provides:
-
-- on-the-fly computation of basis functions for arbitrary cutoff Λ
-- basis functions and singular values are accurate to full precision
-- routines for sparse sampling
-
-We use [tuwien-cms/libxprec](https://github.com/tuwien-cms/libxprec) as a double-double precision arithmetic library.
-
-## Building and Installation
-
-### Dependencies
-
-- **CMake** (>= 3.10)
-- **C++ compiler** with C++11 support
-- **Fortran compiler** (optional, for Fortran bindings)
-
-All other dependencies (including libxprec) are automatically downloaded and built during the build process using CMake's FetchContent feature. You do not need to install these manually.
-
-### Using Build Scripts
-
-Three build scripts are provided for easy building and installation:
-
-1. **build_capi.sh**: Builds and installs only the C API
-   ```bash
-   ./build_capi.sh
-   ```
-
-2. **build_fortran.sh**: Builds and installs the C API and Fortran bindings
-   ```bash
-   ./build_fortran.sh
-   ```
-
-3. **build_with_tests.sh**: Builds everything including tests
-   ```bash
-   ./build_with_tests.sh
-   # After testing, you can install with:
-   cd build && cmake --install .
-   ```
-
-By default, all scripts will install to `$HOME/opt/libsparseir`. You can override this by setting the `CMAKE_INSTALL_PREFIX` environment variable:
-
-```bash
-CMAKE_INSTALL_PREFIX=/usr/local ./build_capi.sh
-```
-
-### Manual Build
-
-If you prefer to build manually, you can use the following commands:
-
-```bash
-mkdir -p build
-cd build
-# For C API only
-cmake .. -DSPARSEIR_BUILD_FORTRAN=OFF -DSPARSEIR_BUILD_TESTING=OFF
-# For C API and Fortran bindings
-cmake .. -DSPARSEIR_BUILD_FORTRAN=ON -DSPARSEIR_BUILD_TESTING=OFF
-# For everything including tests
-cmake .. -DSPARSEIR_BUILD_FORTRAN=ON -DSPARSEIR_BUILD_TESTING=ON
-
-# Build
-cmake --build .
-
-# Install
-cmake --install .
-```
-
-### Quick Test Build
-
-For a quick test build with all options enabled:
-
-```sh
-rm -rf ./build && cmake -S . -B ./build -DSPARSEIR_BUILD_TESTING=ON && cmake --build ./build -j && ./build/test/libsparseirtests
-```
-
-### Testing Fortran Bindings
-
-After building with Fortran bindings enabled, you can run the Fortran test:
-
-```bash
-cd build
-./test_kernel
-```
-
-## Generating documentation with Doxygen
-
-Install `doxygen` and `graphviz`. Then, run the following command:
-
-```bash
-bash generate_docs.sh
-```
-
-This will create the `docs/html` directory. Open `docs/html/index.html` with your browser to see it.
-
-# libsparseir C-API Documentation
-
-This document describes how to use the C-API of libsparseir. The C-API provides a way to use the sparseir library from C or other languages that can interface with C. All objects are immutable.
-
-## Basic Usage
-
-Please refer [`test/cinterface.cxx`](test/cinterface.cxx) to learn more.
-
-
-### Basic Working Example
-The following example demonstrates how to create a fermionic finite-temperature basis using the logistic kernel,
-and perform transformations of a single-variable Green's function between Matsubara frequency and imaginary-time domains.
-
-For fitting, we use the `spir_sampling_fit_XY`, where `X` is the element type of the input data, and `Y` is that of the output data:  `z` corresponds to `c_complex`, `d` to `double`.
-The same naming convention is used for evaluation: `spir_sampling_eval_XY`.
-
-The logistic kernel is defined as
-
-$
-K^\mathrm{L}(\tau, \omega) = \frac{e^{-\tau \omega}}{1 + e^{-\beta\omega}},
-$
-
-which corresponds to the normal Fermi-Dirac distribution at temperature $\beta^{-1}$.
-For more details, see [SparseIR Tutorial](https://spm-lab.github.io/sparse-ir-tutorial/).
-
-```c
-#include <complex.h>
-#include <sparseir/sparseir.h>
-
-// Create a fermionic finite temperature basis
-double beta = 10.0;        // Inverse temperature
-double omega_max = 10.0;   // Ultraviolet cutoff
-double epsilon = 1e-8;     // Accuracy target
-spir_fermionic_finite_temp_basis* basis =
-    spir_fermionic_finite_temp_basis_new(beta, omega_max, epsilon);
-
-// Create sampling objects for imaginary-time and Matsubara domains
-spir_sampling* tau_sampling = spir_fermionic_tau_sampling_new(basis);
-spir_sampling* matsubara_sampling = spir_fermionic_matsubara_sampling_new(basis);
-
-// Create Green's function with a pole at 0.5*omega_max
-int n_matsubara;
-int status = spir_sampling_get_npoints(matsubara_sampling, &n_matsubara);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-
-c_complex* g_matsubara = (c_complex*)malloc(n_matsubara * sizeof(c_complex));
-int* matsubara_indices = (int*)malloc(n_matsubara * sizeof(int));
-
-// Get Matsubara frequency indices
-status = spir_sampling_get_matsus(matsubara_sampling, matsubara_indices);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-
-// Set pole position
-const double pole_position = 0.5 * omega_max;
-
-// Initialize Green's function in Matsubara frequencies
-// G(iω_n) = 1/(iω_n - ε) = ε/(ω_n^2 + ε^2) - iω_n/(ω_n^2 + ε^2)
-for (int i = 0; i < n_matsubara; ++i) {
-    double i_n = (2 * matsubara_indices[i] + 1) * M_PI / beta;  // Fermionic Matsubara frequency
-    double denominator = i_n * i_n + pole_position * pole_position;
-    g_matsubara[i] = c_complex{
-        pole_position / denominator,  // Real part: ε/(ω_n^2 + ε^2)
-        -i_n / denominator           // Imaginary part: -ω_n/(ω_n^2 + ε^2)
-    };
-}
-
-int target_dim = 0; // target dimension for evaluation and fit
-
-// Matsubara sampling points to basis coefficients
-int n_basis;
-status = spir_fermionic_finite_temp_basis_get_size(basis, &n_basis);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-c_complex* g_fit = (c_complex*)malloc(n_basis * sizeof(c_complex));
-int dims[1] = {n_matsubara};
-status = spir_sampling_fit_zz(matsubara_sampling, SPIR_ORDER_COLUMN_MAJOR,
-                             1, dims, target_dim, g_matsubara, g_fit);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-
-// Evaluate the basis coefficients at imaginary times
-{
-    double tau = 0.1 * beta;
-    double expected = -exp(-tau * pole_position) / (1.0 + exp(-beta * pole_position));
-    spir_polyvector* u = spir_fermionic_finite_temp_basis_get_u(basis);
-    double* uval = (double*)malloc(n_basis * sizeof(double));
-    status = spir_evaluate_funcs(u, tau, uval);
-    assert(status == SPIR_COMPUTATION_SUCCESS);
-
-    double actual = 0.0;
-    for (int i = 0; i < n_basis; ++i) {
-        actual += creal(g_fit[i]) * uval[i];
-    }
-    assert(fabs(actual - expected) < epsilon);
-
-    free(uval);
-    spir_release_polyvector(u);
-}
-
-// Basis coefficients to imaginary-time sampling points
-int n_tau;
-status = spir_sampling_get_npoints(tau_sampling, &n_tau);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-c_complex* g_tau = (c_complex*)malloc(n_tau * sizeof(c_complex));
-status = spir_sampling_eval_zz(tau_sampling, SPIR_ORDER_COLUMN_MAJOR,
-                                  1, dims, target_dim, g_fit, g_tau);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-
-// Compare with expected result:
-//   G(tau) = -exp(-tau * pole_position) / (1 + exp(-beta * pole_position))
-double* tau_points = (double*)malloc(n_tau * sizeof(double));
-status = spir_sampling_get_taus(tau_sampling, tau_points);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-for (int i = 0; i < n_tau; ++i) {
-    double tau = tau_points[i];
-    double expected = -exp(-tau * pole_position) / (1.0 + exp(-beta * pole_position));
-    assert(fabs(g_tau[i].real - expected) < epsilon);
-    assert(fabs(g_tau[i].imag) < epsilon);
-}
-
-// Imaginary-time sampling points to basis coefficients
-c_complex* g_fit2 = (c_complex*)malloc(n_basis * sizeof(c_complex));
-status = spir_sampling_fit_zz(tau_sampling, SPIR_ORDER_COLUMN_MAJOR,
-                              1, dims, target_dim, g_tau, g_fit2);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-
-// Basis coefficients to Matsubara Green's function
-c_complex* g_matsubara_reconstructed = (c_complex*)malloc(n_matsubara * sizeof(c_complex));
-status = spir_sampling_eval_zz(matsubara_sampling, SPIR_ORDER_COLUMN_MAJOR,
-                                  1, dims, target_dim, g_fit2, g_matsubara_reconstructed);
-assert(status == SPIR_COMPUTATION_SUCCESS);
-for (int i = 0; i < n_matsubara; ++i) {
-    assert(fabs(g_matsubara_reconstructed[i].real2 - g_matsubara[i].real) < epsilon);
-    assert(fabs(g_matsubara_reconstructed[i].imag - g_matsubara[i].imag) < epsilon);
-}
-
-// Clean up (order is arbitrary)
-free(matsubara_indices);
-free(g_matsubara);
-free(g_fit);
-free(g_tau);
-spir_release_fermionic_finite_temp_basis(basis);
-spir_release_sampling(tau_sampling);
-spir_release_sampling(matsubara_sampling);
-```
-
-
-We can create a bosonic basis using the logistic kernel as discussed in the [SparseIR Tutorial](https://spm-lab.github.io/sparse-ir-tutorial/).
-This can be achived by replacing `fermionic` by `bosonic` in the above code.
-
-
-### Kernel Creation and Domain
-
-```c
-#include <sparseir/sparseir.h>
-
-// Create kernels for different statistics
-spir_kernel* fermionic_kernel = spir_logistic_kernel_new(9.0);
-spir_kernel* bosonic_kernel = spir_reg_bose_kernel_new(9.0);
-
-// Get kernel domain
-double xmin, xmax, ymin, ymax;
-spir_kernel_domain(fermionic_kernel, &xmin, &xmax, &ymin, &ymax);
-
-// Clean up
-spir_release_kernel(fermionic_kernel);
-spir_release_kernel(bosonic_kernel);
-```
-
-### Basis Construction and Sampling
-
-```c
-#include <sparseir/sparseir.h>
-
-// Create a fermionic finite temperature basis
-double beta = 10.0;        // Inverse temperature
-double omega_max = 10.0;   // Frequency cutoff
-double epsilon = 1e-8;     // Accuracy target
-spir_fermionic_finite_temp_basis* basis =
-    spir_fermionic_finite_temp_basis_new(beta, omega_max, epsilon);
-
-// Create sampling objects for different domains
-spir_sampling* tau_sampling = spir_fermionic_tau_sampling_new(basis);
-spir_sampling* matsubara_sampling = spir_fermionic_matsubara_sampling_new(basis);
-
-// Create Green's function with a pole at 0.5*omega_max
-int n_matsubara;
-int status = spir_sampling_get_npoints(matsubara_sampling, &n_matsubara);
-if (status != 0) {
-    // Handle error
-    exit(-1);
-}
-
-c_complex* g_matsubara = (c_complex*)malloc(n_matsubara * sizeof(c_complex));
-int* matsubara_indices = (int*)malloc(n_matsubara * sizeof(int));
-
-// Get Matsubara frequency indices
-status = spir_sampling_get_matsus(matsubara_sampling, matsubara_indices);
-if (status != 0) {
-    // Handle error
-    free(matsubara_indices);
-    free(g_matsubara);
-    exit(-1);
-}
-
-// Set pole position
-const double pole_position = 0.5 * omega_max;
-
-// Initialize Green's function in Matsubara frequencies
-// G(iω_n) = 1/(iω_n - ε) = ε/(ω_n^2 + ε^2) - iω_n/(ω_n^2 + ε^2)
-for (int i = 0; i < n_matsubara; ++i) {
-    double i_n = (2 * matsubara_indices[i] + 1) * M_PI / beta;  // Fermionic Matsubara frequency
-    double denominator = i_n * i_n + pole_position * pole_position;
-    g_matsubara[i] = c_complex{
-        pole_position / denominator,  // Real part: ε/(ω_n^2 + ε^2)
-        -i_n / denominator           // Imaginary part: -ω_n/(ω_n^2 + ε^2)
-    };
-}
-
-// Clean up
-free(matsubara_indices);
-free(g_matsubara);
-spir_release_fermionic_finite_temp_basis(basis);
-spir_release_sampling(tau_sampling);
-spir_release_sampling(matsubara_sampling);
-```
-
-### Sampling Operations
-
-```c
-#include <sparseir/sparseir.h>
-
-// Create basis and sampling objects
-double beta = 10.0;
-double omega_max = 10.0;
-double epsilon = 1e-8;
-spir_fermionic_finite_temp_basis* basis =
-    spir_fermionic_finite_temp_basis_new(beta, omega_max, epsilon);
-spir_sampling* tau_sampling = spir_fermionic_tau_sampling_new(basis);
-
-// Example of evaluating basis coefficients at sampling points
-int32_t ndim = 2;
-int32_t input_dims[] = {3, 4};  // Example dimensions
-int32_t target_dim = 0;
-double input[] = {1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0};
-double output[12];
-
-// Real to real transformation
-spir_sampling_eval_dd(
-    tau_sampling,
-    SPIR_ORDER_COLUMN_MAJOR,
-    ndim,
-    input_dims,
-    target_dim,
-    input,
-    output
-);
-
-// Fit values back to basis coefficients
-spir_sampling_fit_dd(
-    tau_sampling,
-    SPIR_ORDER_COLUMN_MAJOR,
-    ndim,
-    input_dims,
-    target_dim,
-    output,
-    input
-);
-
-// Clean up
-spir_release_fermionic_finite_temp_basis(basis);
-spir_release_sampling(tau_sampling);
-```
-
-### Discrete Lehmann Representation (DLR)
-
-```c
-#include <sparseir/sparseir.h>
-#include <stdlib.h> // rand
-
-double beta = 100.0;
-double wmax = 1.0;
-double epsilon = 1e-12;
-
-spir_fermionic_finite_temp_basis *basis =
-    spir_fermionic_finite_temp_basis_new(beta, wmax, epsilon);
-
-spir_fermionic_dlr *dlr = spir_fermionic_dlr_new(basis);
-
-int npoles = 10;
-double poles[npoles];
-double coeffs[npoles];
-for (int i = 0; i < npoles; i++) {
-    double r = (double)rand() / (double)RAND_MAX;
-    poles[i] = wmax * (2.0 * r - 1.0);
-    r = (double)rand() / (double)RAND_MAX;
-    coeffs[i] = 2.0 * r - 1.0;
-}
-
-spir_fermionic_dlr *dlr_with_poles =
-    spir_fermionic_dlr_new_with_poles(basis, npoles, poles);
-int fitmat_rows = spir_fermionic_dlr_fitmat_rows(dlr_with_poles);
-int fitmat_cols = spir_fermionic_dlr_fitmat_cols(dlr_with_poles);
-
-double *Gl = (double *)malloc(fitmat_rows * sizeof(double));
-int32_t to_ir_input_dims[1] = {npoles};
-int status_to_IR =
-    spir_fermionic_dlr_to_IR(dlr_with_poles, SPIR_ORDER_COLUMN_MAJOR, 1,
-                                to_ir_input_dims, coeffs, Gl);
-
-double *g_dlr = (double *)malloc(fitmat_rows * sizeof(double));
-int32_t from_ir_input_dims[1] = {static_cast<int32_t>(fitmat_rows)};
-int status_from_IR = spir_fermionic_dlr_from_IR(
-    dlr, SPIR_ORDER_COLUMN_MAJOR, 1, from_ir_input_dims, Gl, g_dlr);
-
-// Clean up
-free(Gl);
-free(g_dlr);
-spir_release_fermionic_finite_temp_basis(basis);
-spir_release_fermionic_dlr(dlr);
-spir_release_fermionic_dlr(dlr_with_poles);
-```
-
-### Complex Number Operations
-
-```c
-#include <sparseir/sparseir.h>
-#include <complex.h>
-
-// Create basis and sampling objects
-double beta = 10.0;
-double omega_max = 10.0;
-double epsilon = 1e-8;
-spir_fermionic_finite_temp_basis* basis =
-    spir_fermionic_finite_temp_basis_new(beta, omega_max, epsilon);
-spir_sampling* matsubara_sampling = spir_fermionic_matsubara_sampling_new(basis);
-
-// Setup dimensions and data
-int32_t ndim = 2;
-int32_t input_dims[] = {3, 4};
-int32_t target_dim = 0;
-
-// Initialize complex input data
-c_complex complex_input[12];
-c_complex complex_output[12];
-for (int i = 0; i < 12; i++) {
-    // Complex numbers with real and imaginary parts
-    complex_input[i] = c_complex{(double)i, (double)i};
-}
-
-// Complex to complex transformation
-spir_sampling_eval_zz(
-    matsubara_sampling,
-    SPIR_ORDER_COLUMN_MAJOR,
-    ndim,
-    input_dims,
-    target_dim,
-    complex_input,
-    complex_output
-);
-
-// Fit complex values back to basis coefficients
-c_complex recovered_input[12];
-spir_sampling_fit_zz(
-    matsubara_sampling,
-    SPIR_ORDER_COLUMN_MAJOR,
-    ndim,
-    input_dims,
-    target_dim,
-    complex_output,
-    recovered_input
-);
-
-// Clean up
-spir_release_fermionic_finite_temp_basis(basis);
-spir_release_sampling(matsubara_sampling);
-```
-
-# libsparseir Fortran Bindings Documentation
-
-This document describes how to use the Fortran bindings of libsparseir. The Fortran bindings provide a way to use the sparseir library from Fortran. All objects are immutable.
-
-## Basic Usage
-
-```fortran
-use sparseir
-implicit none
-
-type(spir_kernel) :: kernel
-real(8) :: lambda, xmin, xmax, ymin, ymax
-integer :: stat
-
-! Create a logistic kernel
-lambda = 9.0d0
-kernel = spir_logistic_kernel_new(lambda)
-
-! Get kernel domain
-stat = spir_kernel_domain(kernel, xmin, xmax, ymin, ymax)
-```
\ No newline at end of file
diff --git a/back/_build_fortran.sh b/back/_build_fortran.sh
deleted file mode 100644
index 2ecd1160..00000000
--- a/back/_build_fortran.sh
+++ /dev/null
@@ -1,24 +0,0 @@
-#!/bin/bash
-set -e
-
-# Get script directory
-SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-cd "$SCRIPT_DIR"
-
-# Create build directory
-mkdir -p build
-cd build
-
-# Configure with tests enabled
-cmake .. \
-  -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX:-$HOME/opt/libsparseir} \
-  -DCMAKE_C_FLAGS="-w" \
-  -DCMAKE_CXX_FLAGS="-w" \
-  -DCMAKE_EXE_LINKER_FLAGS="" \
-  -DSPARSEIR_BUILD_FORTRAN=ON \
-  -DSPARSEIR_BUILD_TESTING=OFF \
-  -DSPARSEIR_USE_BLAS=OFF \
-  -DSPARSEIR_USE_LAPACKE=OFF
-
-cmake --build . --config Release -j 4
-make install
diff --git a/back/build_capi.sh b/back/build_capi.sh
deleted file mode 100644
index 5752b81d..00000000
--- a/back/build_capi.sh
+++ /dev/null
@@ -1,25 +0,0 @@
-#!/bin/bash
-set -e
-
-# Get script directory
-SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-cd "$SCRIPT_DIR"
-
-# Clean build directory to ensure clean state
-rm -rf build
-mkdir -p build
-cd build
-
-# Configure with minimal options (only C-API)
-cmake .. \
-  -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX:-$HOME/opt/libsparseir} \
-  -DSPARSEIR_BUILD_FORTRAN=ON \
-  -DSPARSEIR_BUILD_TESTING=OFF \
-  -DSPARSEIR_USE_BLAS=OFF \
-  -DBUILD_TESTING=OFF
-
-# Build and install
-cmake --build . --config Release -- -j 4
-cmake --install .
-
-echo "SparseIR C-API library has been built and installed successfully." 
diff --git a/back/build_capi_with_asan.sh b/back/build_capi_with_asan.sh
deleted file mode 100644
index 9c3905c4..00000000
--- a/back/build_capi_with_asan.sh
+++ /dev/null
@@ -1,30 +0,0 @@
-#!/bin/bash
-set -e
-
-# Get script directory
-SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-cd "$SCRIPT_DIR"
-
-# Create build directory
-mkdir -p build
-cd build
-
-# Configure with tests enabled
-cmake .. \
-  -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX:-$HOME/opt/libsparseir} \
-  -DCMAKE_BUILD_TYPE=Debug \
-  -DCMAKE_C_FLAGS="-w -fsanitize=address -static-libasan" \
-  -DCMAKE_CXX_FLAGS="-w -fsanitize=address -static-libasan" \
-  -DCMAKE_EXE_LINKER_FLAGS="-static-libasan" \
-  -DSPARSEIR_BUILD_FORTRAN=OFF \
-  -DSPARSEIR_BUILD_TESTING=OFF \
-  -DSPARSEIR_USE_BLAS=ON
-
-# Build (including tests)
-cmake --build . --config Release -j 4
-
-# Run tests
-ctest --output-on-failure
-
-echo "SparseIR was built with tests successfully."
-echo "You can install it using: cd build && cmake --install ." 
diff --git a/back/build_optimized.sh b/back/build_optimized.sh
deleted file mode 100644
index cce0cedc..00000000
--- a/back/build_optimized.sh
+++ /dev/null
@@ -1,32 +0,0 @@
-#!/bin/bash
-set -e
-
-# Get script directory
-SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-cd "$SCRIPT_DIR"
-
-# Clean build directory to ensure clean state
-rm -rf build
-mkdir -p build
-cd build
-
-# Configure with maximum optimization for benchmarking
-cmake .. \
-  -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX:-$HOME/opt/libsparseir} \
-  -DSPARSEIR_BUILD_FORTRAN=ON \
-  -DSPARSEIR_BUILD_TESTING=OFF \
-  -DSPARSEIR_USE_BLAS=OFF \
-  -DBUILD_TESTING=OFF \
-  -DCMAKE_BUILD_TYPE=Release \
-  -DCMAKE_CXX_FLAGS="-O3 -DNDEBUG -g0 -march=native" \
-  -DCMAKE_EXE_LINKER_FLAGS="-flto" \
-  -DCMAKE_VERBOSE_MAKEFILE=ON
-
-# Build with maximum parallelization
-cmake --build . --config Release -- -j $(nproc)
-
-# Install
-cmake --install .
-
-echo "Optimized SparseIR library has been built and installed successfully."
-echo "Debug symbols removed, maximum optimization enabled."
diff --git a/back/build_with_tests.sh b/back/build_with_tests.sh
deleted file mode 100755
index fb7f214c..00000000
--- a/back/build_with_tests.sh
+++ /dev/null
@@ -1,29 +0,0 @@
-#!/bin/bash
-set -e
-
-# Get script directory
-SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-cd "$SCRIPT_DIR"
-
-# Create build directory
-mkdir -p build
-cd build
-
-# Configure with tests enabled
-cmake .. \
-  -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX:-$HOME/opt/libsparseir} \
-  -DCMAKE_C_FLAGS="-w" \
-  -DCMAKE_CXX_FLAGS="-w" \
-  -DCMAKE_EXE_LINKER_FLAGS="" \
-  -DSPARSEIR_BUILD_FORTRAN=ON \
-  -DSPARSEIR_BUILD_TESTING=ON \
-  -DSPARSEIR_USE_BLAS=ON
-
-# Build (including tests)
-cmake --build . --config Release -j 4
-
-# Run tests
-ctest --output-on-failure
-
-echo "SparseIR was built with tests successfully."
-echo "You can install it using: cd build && cmake --install ." 
diff --git a/back/workflows/CI_C_API_Python.yml b/back/workflows/CI_C_API_Python.yml
deleted file mode 100644
index 506d1f68..00000000
--- a/back/workflows/CI_C_API_Python.yml
+++ /dev/null
@@ -1,55 +0,0 @@
-name: Python C API CI
-
-on:
-  push:
-    branches: [ "main" ]
-  pull_request:
-    branches: [ "main" ]
-
-jobs:
-  test:
-    name: Test
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        os: [ubuntu-latest, macos-latest]
-        python-version:
-          - "3.10"
-          - "3.11"
-          - "3.12"
-
-    steps:
-      - name: Install dependencies (Linux)
-        if: runner.os == 'Linux'
-        run: sudo apt update && sudo apt install -y libeigen3-dev libopenblas-dev
-
-      - name: Install dependencies (macOS)
-        if: runner.os == 'macOS'
-        run: brew install eigen openblas
-      - uses: actions/checkout@v5
-      - name: Install uv and set the python version
-        uses: astral-sh/setup-uv@v7
-        with:
-          # Install a specific version of uv.
-          version: "0.8.15"
-          python-version: ${{ matrix.python-version }}
-      - name: Enable caching
-        uses: astral-sh/setup-uv@v7
-        with:
-          enable-cache: true
-      - name: Run prepare_build.py
-        run: python3 prepare_build.py
-        working-directory: python
-
-      - name: Run uv sync
-        run: uv sync
-        working-directory: python
-        env:
-          SPARSEIR_USE_BLAS: 1
-
-      - name: Run tests
-        # For example, using `pytest`
-        run: uv run pytest tests
-        working-directory: python
-        env:
-          SPARSEIR_USE_BLAS: 1
diff --git a/back/workflows/CI_PublishTestPyPI.yml b/back/workflows/CI_PublishTestPyPI.yml
deleted file mode 100644
index 059a7cd2..00000000
--- a/back/workflows/CI_PublishTestPyPI.yml
+++ /dev/null
@@ -1,87 +0,0 @@
-name: CI Python Build & Publish to TestPyPI (Trusted)
-
-on:
-  push:
-    tags: ["v*"]
-  workflow_dispatch:
-
-jobs:
-  build-wheels:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        include:
-          # Linux builds
-          - os: ubuntu-latest
-            cibw_archs: "auto"
-            deployment_target: ""
-            openblas_path: ""
-            py_tag: "cp310"
-          # macOS Intel builds
-          - os: macos-13  # Intel Mac
-            cibw_archs: "x86_64"
-            deployment_target: "13.0"
-            openblas_path: "/usr/local/opt/openblas"
-            py_tag: "cp310"
-          # macOS Apple Silicon builds
-          - os: macos-latest  # Apple Silicon Mac
-            cibw_archs: "arm64"
-            deployment_target: "15.0"
-            openblas_path: "/opt/homebrew/opt/openblas"
-            py_tag: "cp310"
-    steps:
-      - uses: actions/checkout@v5
-      - name: remove python/.gitignore
-        shell: bash
-        run: |
-          rm -f python/.gitignore
-      - name: prepare build
-        shell: bash
-        run: |
-          cd python
-          python prepare_build.py
-      - uses: pypa/cibuildwheel@v3.2.1
-        env:
-          CIBW_DEPENDENCY_VERSIONS: "latest"
-          CIBW_BUILD_VERBOSITY: 1
-          CIBW_MANYLINUX_X86_64_IMAGE: "manylinux_2_28"
-          CIBW_BUILD: "${{ matrix.py_tag }}-*"
-          CIBW_ENVIRONMENT_MACOS: "MACOSX_DEPLOYMENT_TARGET=${{ matrix.deployment_target || '11.0' }} SPARSEIR_USE_BLAS=1"
-          CIBW_ARCHS: ${{ matrix.cibw_archs }}
-          CIBW_SKIP: "*-manylinux_i686 *-musllinux_i686"
-          # Install OpenBLAS using micromamba (conda-forge) - separate for manylinux and musllinux
-          CIBW_BEFORE_ALL_MANYLINUX: "curl -Ls https://micro.mamba.pm/api/micromamba/linux-64/latest | tar -xvj bin/micromamba && ./bin/micromamba create -y -p /opt/openblas && ./bin/micromamba install -y -c conda-forge openblas -p /opt/openblas --no-deps"
-          CIBW_BEFORE_ALL_MUSLLINUX: "apk add --no-cache bzip2 && curl -Ls https://micro.mamba.pm/api/micromamba/linux-64/latest | tar -xvj bin/micromamba && ./bin/micromamba create -y -p /opt/openblas && ./bin/micromamba install -y -c conda-forge openblas -p /opt/openblas --no-deps"
-          CIBW_BEFORE_ALL_MACOS: "brew install openblas"
-          # Set environment variables to help CMake find OpenBLAS
-          CIBW_ENVIRONMENT_MANYLINUX: "SPARSEIR_USE_BLAS=1"
-          CIBW_ENVIRONMENT_MUSLLINUX: "SPARSEIR_USE_BLAS=1"
-        with:
-          package-dir: ./python
-          output-dir: dist
-      - uses: actions/upload-artifact@v5
-        with:
-          name: wheels-${{ matrix.os }}-${{ matrix.cibw_archs }}-${{ matrix.py_tag }}
-          path: dist/*
-
-  publish-testpypi:
-    needs: build-wheels
-    runs-on: ubuntu-latest
-    environment:
-      name: testpypi
-    permissions:
-      id-token: write     # ← Trusted Publishing に必須
-      contents: read
-    steps:
-      - uses: actions/download-artifact@v6
-        with:
-          path: dist
-          merge-multiple: true
-      - name: Publish to TestPyPI (Trusted)
-        uses: pypa/gh-action-pypi-publish@release/v1
-        with:
-          packages-dir: dist
-          repository-url: https://test.pypi.org/legacy/
-          verbose: true
-          skip-existing: true
-          attestations: false  # Disable attestations due to Sigstore service issues
\ No newline at end of file
diff --git a/back/workflows/CI_cmake_intel.yml b/back/workflows/CI_cmake_intel.yml
deleted file mode 100644
index 865cf973..00000000
--- a/back/workflows/CI_cmake_intel.yml
+++ /dev/null
@@ -1,142 +0,0 @@
-# CMake CI workflow for libsparseir with Intel oneAPI compilers
-# Tests on Ubuntu-latest (x86_64) with Intel C++/Fortran compilers
-name: CMake Intel oneAPI CI
-
-on:
-  push:
-    branches: [ "main" ]
-  pull_request:
-    branches: [ "main" ]
-
-env:
-  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
-  BUILD_TYPE: Release
-  INSTALL_PREFIX: ${{github.workspace}}/install
-
-jobs:
-  build-intel:
-    runs-on: ubuntu-latest
-    name: ubuntu-latest-intel-x86_64
-
-    steps:
-    - uses: actions/checkout@v5
-
-    - name: Install Intel oneAPI Base Toolkit
-      run: |
-        # Download Intel oneAPI GPG public key
-        wget -O- https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS.PUB | gpg --dearmor | sudo tee /usr/share/keyrings/oneapi-archive-keyring.gpg > /dev/null
-        
-        # Add Intel oneAPI repository
-        echo "deb [signed-by=/usr/share/keyrings/oneapi-archive-keyring.gpg] https://apt.repos.intel.com/oneapi all main" | sudo tee /etc/apt/sources.list.d/oneAPI.list
-        
-        # Update package list
-        sudo apt-get update
-        
-        # Install Intel oneAPI compilers
-        sudo apt-get install -y intel-oneapi-compiler-dpcpp-cpp intel-oneapi-compiler-fortran intel-oneapi-mkl-devel
-
-    - name: Install Eigen
-      run: sudo apt-get install -y libeigen3-dev
-
-    - name: Setup Intel oneAPI environment
-      run: |
-        source /opt/intel/oneapi/setvars.sh
-        echo "Intel C++ compiler: $(which icpx)"
-        echo "Intel Fortran compiler: $(which ifx)"
-        icpx --version
-        ifx --version
-
-    - name: Configure CMake
-      run: |
-        source /opt/intel/oneapi/setvars.sh
-        
-        cmake -B ${{github.workspace}}/build \
-          -DCMAKE_C_COMPILER=icx \
-          -DCMAKE_CXX_COMPILER=icpx \
-          -DCMAKE_CXX_FLAGS="-fp-model=precise -g -O2" \
-          -DCMAKE_Fortran_COMPILER=ifx \
-          -DCMAKE_Fortran_FLAGS="-stand f08 -warn all -g -O2 -check bounds -traceback" \
-          -DCMAKE_BUILD_TYPE=Release \
-          -DSPARSEIR_BUILD_FORTRAN=ON \
-          -DCMAKE_INSTALL_PREFIX=${{env.INSTALL_PREFIX}} \
-          -DSPARSEIR_BUILD_TESTING=OFF \
-          -DSPARSEIR_USE_BLAS=OFF \
-          -DSPARSEIR_DEBUG=ON
-
-    - name: Build
-      run: |
-        source /opt/intel/oneapi/setvars.sh
-        cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Skip C++/C Tests
-      run: |
-        echo "Skipping C++/C tests to focus on Fortran sample debugging"
-
-    - name: Install
-      run: |
-        source /opt/intel/oneapi/setvars.sh
-        cmake --install ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Verify Installation
-      run: |
-        ls -la ${{env.INSTALL_PREFIX}}/include/sparseir/
-        ls -la ${{env.INSTALL_PREFIX}}/lib/
-
-    - name: Build and Run Fortran Sample
-      run: |
-        source /opt/intel/oneapi/setvars.sh
-        
-        echo "=== Building Fortran Sample ==="
-        cd fortran/sample
-        
-        # Find SparseIR CMake config
-        SPARSEIR_DIR="${{env.INSTALL_PREFIX}}/share/cmake/SparseIR"
-        if [ ! -d "$SPARSEIR_DIR" ]; then
-          echo "ERROR: SparseIR CMake config not found at $SPARSEIR_DIR"
-          exit 1
-        fi
-        
-        # Install FFTW3
-        sudo apt-get update && sudo apt-get install -y libfftw3-dev
-        
-        # Clean and build
-        rm -rf build
-        
-        cmake -B build \
-          -DSparseIR_DIR="$SPARSEIR_DIR" \
-          -DUSE_SYSTEM_LIBSPARSEIR=ON \
-          -DCMAKE_BUILD_TYPE=Release \
-          -DCMAKE_Fortran_COMPILER=ifx \
-          -DCMAKE_Fortran_FLAGS="-stand f08 -warn all -g -O2 -check bounds -traceback"
-        
-        cmake --build build
-        
-        echo "=== Running Fortran Sample ==="
-        
-        export LD_LIBRARY_PATH="${{env.INSTALL_PREFIX}}/lib:$LD_LIBRARY_PATH"
-        export SPARSEIR_DEBUG=1
-        echo "Set library paths:"
-        echo "LD_LIBRARY_PATH: $LD_LIBRARY_PATH"
-        echo "SPARSEIR_DEBUG: $SPARSEIR_DEBUG"
-        
-        # Run with error handling and debug tools
-        if ./build/second_order_perturbation_fort; then
-          echo "=== Fortran Sample completed successfully ==="
-        else
-          echo "=== Fortran Sample failed with exit code $? ==="
-          echo "=== Running with debug tools ==="
-          
-          # Install debug tools
-          sudo apt-get install -y gdb valgrind
-          
-          # Run with gdb for stack trace
-          echo "=== GDB Stack Trace ==="
-          gdb -batch -ex "run" -ex "bt" -ex "info registers" -ex "quit" ./build/second_order_perturbation_fort 2>&1 || true
-          
-          # Run with valgrind for memory debugging
-          echo "=== Valgrind Memory Check ==="
-          valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all --track-origins=yes ./build/second_order_perturbation_fort 2>&1 || true
-          
-          exit 1
-        fi
-
diff --git a/back/workflows/CI_cmake_no_blas.yml b/back/workflows/CI_cmake_no_blas.yml
deleted file mode 100644
index b4a2a294..00000000
--- a/back/workflows/CI_cmake_no_blas.yml
+++ /dev/null
@@ -1,160 +0,0 @@
-# Multi-platform CMake CI workflow for libsparseir (without BLAS)
-# Tests across Windows, macOS, and Ubuntu with gcc and clang compilers
-name: CMake Multi-Platform CI (No BLAS)
-
-on:
-  push:
-    branches: [ "main" ]
-  pull_request:
-    branches: [ "main" ]
-
-env:
-  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
-  BUILD_TYPE: Release
-  INSTALL_PREFIX: ${{github.workspace}}/install
-
-jobs:
-  build-no-blas:
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          # Ubuntu with gcc and clang (x86_64)
-          - os: ubuntu-latest
-            compiler: gcc
-            c_compiler: gcc
-            cpp_compiler: g++
-            eigen_install: sudo apt update && sudo apt install -y libeigen3-dev
-          - os: ubuntu-latest
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            eigen_install: sudo apt update && sudo apt install -y libeigen3-dev
-
-          # Ubuntu ARM64 with gcc and clang
-          - os: ubuntu-latest
-            arch: arm64
-            compiler: gcc
-            c_compiler: gcc
-            cpp_compiler: g++
-            eigen_install: sudo apt update && sudo apt install -y libeigen3-dev
-          - os: ubuntu-latest
-            arch: arm64
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            eigen_install: sudo apt update && sudo apt install -y libeigen3-dev
-
-          # macOS with clang
-          - os: macos-latest
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            eigen_install: brew install eigen
-
-    runs-on: ${{ matrix.os }}
-    name: ${{ matrix.os }}-${{ matrix.compiler }}${{ matrix.arch && format('-{0}', matrix.arch) || '' }}-no-blas
-
-    steps:
-    - uses: actions/checkout@v5
-
-    - name: Install Fortran compiler (macOS)
-      if: matrix.os == 'macos-latest'
-      run: brew install gfortran
-
-    - name: Install Eigen
-      run: ${{ matrix.eigen_install }}
-
-    - name: Debug Fortran compilers (macOS)
-      if: matrix.os == 'macos-latest'
-      run: |
-        echo "Available Fortran compilers:"
-        ls -la /opt/homebrew/bin/*fortran* || echo "No *fortran* found in /opt/homebrew/bin/"
-        ls -la /usr/local/bin/*fortran* || echo "No *fortran* found in /usr/local/bin/"
-        which gfortran || echo "gfortran not in PATH"
-        which gfortran-13 || echo "gfortran-13 not in PATH"
-
-    - name: Configure CMake (Unix)
-      run: |
-        if [[ "${{ matrix.os }}" == "macos-latest" ]]; then
-          # Use the full path to gfortran from Homebrew gcc
-          FORTRAN_COMPILER="/opt/homebrew/bin/gfortran-13"
-        else
-          FORTRAN_COMPILER="gfortran"
-        fi
-
-        cmake -B ${{github.workspace}}/build \
-          -DCMAKE_C_COMPILER=${{ matrix.c_compiler }} \
-          -DCMAKE_CXX_COMPILER=${{ matrix.cpp_compiler }} \
-          -DCMAKE_Fortran_COMPILER="$FORTRAN_COMPILER" \
-          -DCMAKE_Fortran_FLAGS="-std=f2008 -pedantic -Wall -Wextra" \
-          -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
-          -DSPARSEIR_BUILD_FORTRAN=ON \
-          -DCMAKE_INSTALL_PREFIX=${{env.INSTALL_PREFIX}} \
-          -DSPARSEIR_BUILD_TESTING=ON \
-          -DSPARSEIR_USE_BLAS=OFF
-
-    - name: Build
-      run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Test
-      working-directory: ${{github.workspace}}/build
-      run: ctest --build-config ${{env.BUILD_TYPE}} --output-on-failure
-
-    - name: Install
-      run: cmake --install ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Verify Installation
-      run: |
-        ls -la ${{env.INSTALL_PREFIX}}/include/sparseir/
-        ls -la ${{env.INSTALL_PREFIX}}/lib/
-
-    - name: Build and Run Fortran Sample (Unix)
-      run: |
-        echo "=== Building Fortran Sample ==="
-        cd fortran/sample
-        
-        # Find SparseIR CMake config
-        SPARSEIR_DIR="${{env.INSTALL_PREFIX}}/share/cmake/SparseIR"
-        if [ ! -d "$SPARSEIR_DIR" ]; then
-          echo "ERROR: SparseIR CMake config not found at $SPARSEIR_DIR"
-          exit 1
-        fi
-        
-        # Install FFTW3 if needed (for Ubuntu/macOS)
-        if [[ "${{ matrix.os }}" == "ubuntu-latest" ]]; then
-          sudo apt-get update && sudo apt-get install -y libfftw3-dev
-        elif [[ "${{ matrix.os }}" == "macos-latest" ]]; then
-          brew install fftw
-        fi
-        
-        # Clean and build
-        rm -rf build
-        
-        # Set Fortran compiler explicitly
-        if [[ "${{ matrix.os }}" == "macos-latest" ]]; then
-          FORTRAN_COMPILER="/opt/homebrew/bin/gfortran-13"
-        else
-          FORTRAN_COMPILER="gfortran"
-        fi
-        
-        cmake -B build \
-          -DSparseIR_DIR="$SPARSEIR_DIR" \
-          -DUSE_SYSTEM_LIBSPARSEIR=ON \
-          -DCMAKE_BUILD_TYPE=Release \
-          -DCMAKE_Fortran_COMPILER="$FORTRAN_COMPILER" \
-          -DCMAKE_Fortran_FLAGS="-std=f2008 -pedantic -Wall -Wextra"
-        
-        cmake --build build
-        
-        echo "=== Running Fortran Sample ==="
-        
-        export LD_LIBRARY_PATH="${{env.INSTALL_PREFIX}}/lib:$LD_LIBRARY_PATH"
-        export DYLD_LIBRARY_PATH="${{env.INSTALL_PREFIX}}/lib:$DYLD_LIBRARY_PATH"
-        echo "Set library paths:"
-        echo "LD_LIBRARY_PATH: $LD_LIBRARY_PATH"
-        echo "DYLD_LIBRARY_PATH: $DYLD_LIBRARY_PATH"
-        
-        ./build/second_order_perturbation_fort
-        
-        echo "=== Fortran Sample completed successfully ==="
diff --git a/back/workflows/CI_cmake_with_blas.yml b/back/workflows/CI_cmake_with_blas.yml
deleted file mode 100644
index 0515e854..00000000
--- a/back/workflows/CI_cmake_with_blas.yml
+++ /dev/null
@@ -1,201 +0,0 @@
-# Multi-platform CMake CI workflow for libsparseir (with BLAS/OpenBLAS)
-# Tests across Ubuntu and macOS with BLAS/LAPACK support
-name: CMake Multi-Platform CI (With BLAS)
-
-on:
-  push:
-    branches: [ "main" ]
-  pull_request:
-    branches: [ "main" ]
-
-env:
-  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
-  BUILD_TYPE: Release
-  INSTALL_PREFIX: ${{github.workspace}}/install
-
-jobs:
-  build-with-blas:
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          # Ubuntu with gcc and clang (BLAS/LAPACK enabled) - x86_64
-          - os: ubuntu-latest
-            compiler: gcc
-            c_compiler: gcc
-            cpp_compiler: g++
-            deps_install: sudo apt update && sudo apt install -y libeigen3-dev libblas-dev liblapack-dev
-          - os: ubuntu-latest
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            deps_install: sudo apt update && sudo apt install -y libeigen3-dev libblas-dev liblapack-dev
-
-          # Ubuntu ARM64 with gcc and clang (BLAS/LAPACK enabled)
-          - os: ubuntu-latest
-            arch: arm64
-            compiler: gcc
-            c_compiler: gcc
-            cpp_compiler: g++
-            deps_install: sudo apt update && sudo apt install -y libeigen3-dev libblas-dev liblapack-dev
-          - os: ubuntu-latest
-            arch: arm64
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            deps_install: sudo apt update && sudo apt install -y libeigen3-dev libblas-dev liblapack-dev
-
-          # Ubuntu with OpenBLAS specifically
-          - os: ubuntu-latest
-            compiler: gcc
-            c_compiler: gcc
-            cpp_compiler: g++
-            blas_type: openblas
-            deps_install: sudo apt update && sudo apt install -y libeigen3-dev libopenblas-dev
-          - os: ubuntu-latest
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            blas_type: openblas
-            deps_install: sudo apt update && sudo apt install -y libeigen3-dev libopenblas-dev
-
-          # macOS with BLAS (using Accelerate framework)
-          - os: macos-latest
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            blas_type: accelerate
-            deps_install: brew install eigen
-
-          # macOS with OpenBLAS
-          - os: macos-latest
-            compiler: clang
-            c_compiler: clang
-            cpp_compiler: clang++
-            blas_type: openblas
-            deps_install: brew install eigen openblas
-
-    runs-on: ${{ matrix.os }}
-    name: ${{ matrix.os }}-${{ matrix.compiler }}${{ matrix.arch && format('-{0}', matrix.arch) || '' }}${{ matrix.blas_type && format('-{0}', matrix.blas_type) || '' }}-blas
-
-    steps:
-    - uses: actions/checkout@v5
-
-    - name: Install Fortran compiler (macOS)
-      if: matrix.os == 'macos-latest'
-      run: brew install gfortran
-
-    - name: Install dependencies
-      run: ${{ matrix.deps_install }}
-
-    - name: Debug Fortran compilers (macOS)
-      if: matrix.os == 'macos-latest'
-      run: |
-        echo "Available Fortran compilers:"
-        ls -la /opt/homebrew/bin/*fortran* || echo "No *fortran* found in /opt/homebrew/bin/"
-        ls -la /usr/local/bin/*fortran* || echo "No *fortran* found in /usr/local/bin/"
-        which gfortran || echo "gfortran not in PATH"
-        which gfortran-13 || echo "gfortran-13 not in PATH"
-
-    - name: Configure CMake
-      run: |
-        if [[ "${{ matrix.os }}" == "macos-latest" ]]; then
-          # Use the full path to gfortran from Homebrew gcc
-          FORTRAN_COMPILER="/opt/homebrew/bin/gfortran-13"
-          
-          # Set OpenBLAS paths for macOS if using OpenBLAS
-          if [[ "${{ matrix.blas_type }}" == "openblas" ]]; then
-            OPENBLAS_ROOT="/opt/homebrew/opt/openblas"
-            export LDFLAGS="-L${OPENBLAS_ROOT}/lib"
-            export CPPFLAGS="-I${OPENBLAS_ROOT}/include"
-            export PKG_CONFIG_PATH="${OPENBLAS_ROOT}/lib/pkgconfig"
-          fi
-        else
-          FORTRAN_COMPILER="gfortran"
-        fi
-
-        cmake -B ${{github.workspace}}/build \
-          -DCMAKE_C_COMPILER=${{ matrix.c_compiler }} \
-          -DCMAKE_CXX_COMPILER=${{ matrix.cpp_compiler }} \
-          -DCMAKE_Fortran_COMPILER="$FORTRAN_COMPILER" \
-          -DCMAKE_Fortran_FLAGS="-std=f2008 -pedantic -Wall -Wextra" \
-          -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
-          -DSPARSEIR_BUILD_FORTRAN=ON \
-          -DCMAKE_INSTALL_PREFIX=${{env.INSTALL_PREFIX}} \
-          -DSPARSEIR_BUILD_TESTING=ON \
-          -DSPARSEIR_USE_BLAS=ON
-
-    - name: Build
-      run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Test
-      working-directory: ${{github.workspace}}/build
-      run: ctest --build-config ${{env.BUILD_TYPE}} --output-on-failure
-
-    - name: Install
-      run: cmake --install ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Verify Installation
-      run: |
-        ls -la ${{env.INSTALL_PREFIX}}/include/sparseir/
-        ls -la ${{env.INSTALL_PREFIX}}/lib/
-
-    - name: Check BLAS linking
-      run: |
-        if [[ "${{ matrix.os }}" == "macos-latest" ]]; then
-          otool -L ${{env.INSTALL_PREFIX}}/lib/libsparseir.dylib | grep -E "(Accelerate|openblas)" || echo "No BLAS library found in linking"
-        else
-          ldd ${{env.INSTALL_PREFIX}}/lib/libsparseir.so | grep -E "(blas|lapack|openblas)" || echo "No BLAS library found in linking"
-        fi
-
-    - name: Build and Run Fortran Sample
-      run: |
-        echo "=== Building Fortran Sample ==="
-        cd fortran/sample
-        
-        # Find SparseIR CMake config
-        SPARSEIR_DIR="${{env.INSTALL_PREFIX}}/share/cmake/SparseIR"
-        if [ ! -d "$SPARSEIR_DIR" ]; then
-          echo "ERROR: SparseIR CMake config not found at $SPARSEIR_DIR"
-          exit 1
-        fi
-        
-        # Install FFTW3 if needed
-        if [[ "${{ matrix.os }}" == "ubuntu-latest" ]]; then
-          sudo apt-get update && sudo apt-get install -y libfftw3-dev
-        elif [[ "${{ matrix.os }}" == "macos-latest" ]]; then
-          # FFTW3 might already be installed via deps_install, but ensure it's available
-          brew list fftw || brew install fftw
-        fi
-        
-        # Clean and build
-        rm -rf build
-        
-        # Set Fortran compiler explicitly
-        if [[ "${{ matrix.os }}" == "macos-latest" ]]; then
-          FORTRAN_COMPILER="/opt/homebrew/bin/gfortran-13"
-        else
-          FORTRAN_COMPILER="gfortran"
-        fi
-        
-        cmake -B build \
-          -DSparseIR_DIR="$SPARSEIR_DIR" \
-          -DUSE_SYSTEM_LIBSPARSEIR=ON \
-          -DCMAKE_BUILD_TYPE=Release \
-          -DCMAKE_Fortran_COMPILER="$FORTRAN_COMPILER" \
-          -DCMAKE_Fortran_FLAGS="-std=f2008 -pedantic -Wall -Wextra"
-        
-        cmake --build build
-        
-        echo "=== Running Fortran Sample ==="
-        
-        export LD_LIBRARY_PATH="${{env.INSTALL_PREFIX}}/lib:$LD_LIBRARY_PATH"
-        export DYLD_LIBRARY_PATH="${{env.INSTALL_PREFIX}}/lib:$DYLD_LIBRARY_PATH"
-        echo "Set library paths:"
-        echo "LD_LIBRARY_PATH: $LD_LIBRARY_PATH"
-        echo "DYLD_LIBRARY_PATH: $DYLD_LIBRARY_PATH"
-        
-        ./build/second_order_perturbation_fort
-        
-        echo "=== Fortran Sample completed successfully ==="
-
diff --git a/back/workflows/CI_cmake_with_blas_ilp64.yml b/back/workflows/CI_cmake_with_blas_ilp64.yml
deleted file mode 100644
index 71df8984..00000000
--- a/back/workflows/CI_cmake_with_blas_ilp64.yml
+++ /dev/null
@@ -1,134 +0,0 @@
-# Multi-platform CMake CI workflow for libsparseir (with ILP64 BLAS/OpenBLAS)
-# Tests ILP64 support with OpenBLAS 64-bit integer interface
-name: CMake Multi-Platform CI (With ILP64 BLAS)
-
-on:
-  push:
-    branches: [ "main" ]
-  pull_request:
-    branches: [ "main" ]
-
-env:
-  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
-  BUILD_TYPE: Release
-  INSTALL_PREFIX: ${{github.workspace}}/install
-
-jobs:
-  build-with-ilp64-blas:
-    runs-on: ubuntu-latest
-    name: ubuntu-gcc-ilp64-blas
-
-    steps:
-    - uses: actions/checkout@v5
-
-    - name: Install dependencies
-      run: sudo apt update && sudo apt install -y libeigen3-dev libopenblas64-0 libopenblas64-dev
-
-    - name: Verify OpenBLAS ILP64 installation
-      run: |
-        echo "=== Checking OpenBLAS ILP64 installation ==="
-        dpkg -l | grep openblas64 || echo "No openblas64 packages found"
-        
-        # Check for ILP64 libraries in common locations
-        echo "=== Checking for ILP64 libraries ==="
-        find /usr/lib -name "*openblas64*" -type f 2>/dev/null || echo "No openblas64 libraries found"
-        
-        # Check if ILP64 symbols are available
-        echo "=== Checking for ILP64 symbols ==="
-        for lib in /usr/lib/x86_64-linux-gnu/libopenblas64*.so*; do
-          if [ -f "$lib" ]; then
-            echo "Checking symbols in $lib:"
-            nm -D "$lib" 2>/dev/null | grep -E "dgemm_|zgemm_" | head -3 || echo "No BLAS symbols found"
-            break
-          fi
-        done
-
-    - name: Configure CMake with ILP64
-      run: |
-        # Set environment variables to help CMake find ILP64 BLAS
-        export BLA_VENDOR=OpenBLAS
-        export BLA_PREFER_PKGCONFIG=ON
-        
-        # Find the actual OpenBLAS64 library path
-        OPENBLAS64_LIB=$(find /usr/lib -name "libopenblas64*.so*" -type f | head -1)
-        if [ -z "$OPENBLAS64_LIB" ]; then
-          echo "Error: libopenblas64 not found"
-          exit 1
-        fi
-        echo "Found OpenBLAS64 library: $OPENBLAS64_LIB"
-        
-        # Configure CMake with explicit library hint
-        cmake -B ${{github.workspace}}/build \
-          -DCMAKE_C_COMPILER=gcc \
-          -DCMAKE_CXX_COMPILER=g++ \
-          -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} \
-          -DSPARSEIR_BUILD_FORTRAN=ON \
-          -DCMAKE_INSTALL_PREFIX=${{env.INSTALL_PREFIX}} \
-          -DSPARSEIR_BUILD_TESTING=ON \
-          -DSPARSEIR_USE_BLAS=ON \
-          -DSPARSEIR_USE_ILP64=ON \
-          -DBLAS_LIBRARIES="$OPENBLAS64_LIB"
-
-    - name: Build
-      run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Test
-      working-directory: ${{github.workspace}}/build
-      run: ctest --build-config ${{env.BUILD_TYPE}} --output-on-failure
-
-    - name: Install
-      run: cmake --install ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
-
-    - name: Verify Installation
-      run: |
-        ls -la ${{env.INSTALL_PREFIX}}/include/sparseir/
-        ls -la ${{env.INSTALL_PREFIX}}/lib/
-
-    - name: Check ILP64 BLAS linking
-      run: |
-        echo "=== Checking ILP64 BLAS linking ==="
-        ldd ${{env.INSTALL_PREFIX}}/lib/libsparseir.so | grep -E "(openblas64|blas)" || echo "No BLAS library found in linking"
-        
-        # Verify that the library links to OpenBLAS 64-bit
-        if ldd ${{env.INSTALL_PREFIX}}/lib/libsparseir.so | grep -q "openblas64"; then
-          echo "✓ Successfully linked to OpenBLAS ILP64"
-        else
-          echo "✗ Failed to link to OpenBLAS ILP64"
-          exit 1
-        fi
-
-    - name: Build and Run Fortran Sample with ILP64
-      run: |
-        echo "=== Building Fortran Sample with ILP64 ==="
-        cd fortran/sample
-        
-        # Find SparseIR CMake config
-        SPARSEIR_DIR="${{env.INSTALL_PREFIX}}/share/cmake/SparseIR"
-        if [ ! -d "$SPARSEIR_DIR" ]; then
-          echo "ERROR: SparseIR CMake config not found at $SPARSEIR_DIR"
-          exit 1
-        fi
-        
-        # Install FFTW3 if needed
-        sudo apt-get update && sudo apt-get install -y libfftw3-dev
-        
-        # Clean and build
-        rm -rf build
-        
-        cmake -B build \
-          -DSparseIR_DIR="$SPARSEIR_DIR" \
-          -DUSE_SYSTEM_LIBSPARSEIR=ON \
-          -DCMAKE_BUILD_TYPE=Release \
-          -DCMAKE_Fortran_COMPILER="gfortran"
-        
-        cmake --build build
-        
-        echo "=== Running Fortran Sample with ILP64 ==="
-        
-        export LD_LIBRARY_PATH="${{env.INSTALL_PREFIX}}/lib:$LD_LIBRARY_PATH"
-        echo "Set library paths:"
-        echo "LD_LIBRARY_PATH: $LD_LIBRARY_PATH"
-        
-        ./build/second_order_perturbation_fort
-        
-        echo "=== Fortran Sample with ILP64 completed successfully ==="
diff --git a/back/workflows/CreateTag.yml b/back/workflows/CreateTag.yml
deleted file mode 100644
index 235218f6..00000000
--- a/back/workflows/CreateTag.yml
+++ /dev/null
@@ -1,62 +0,0 @@
-name: Create Tag and Release from Version Header
-on:
-  push:
-    branches: [main]
-
-# https://stackoverflow.com/questions/69063452/github-actions-on-release-created-workflow-trigger-not-working
-# GITHUB_TOKEN is not enough to trigger the wheel build and publish workflow.
-# Use personal access token for "actions" and "contents" read-write permissions.
-
-jobs:
-  tag-and-release:
-    runs-on: ubuntu-latest
-    env:
-      GH_TOKEN: ${{ secrets.DEPLOY }}
-    steps:
-    - uses: actions/checkout@v5
-
-    - name: Set up Python
-      uses: actions/setup-python@v6
-      with:
-        python-version: '3.11'
-
-    - name: Check version consistency
-      run: |
-        echo "Checking version consistency across components..."
-        python update_version.py
-        if [ $? -ne 0 ]; then
-          echo "❌ Version inconsistency detected. Please run 'python update_version.py <version>' to fix."
-          exit 1
-        fi
-        echo "✅ All versions are consistent"
-
-    - name: Extract version from header
-      id: version
-      run: |
-        MAJOR=$(grep "#define SPARSEIR_VERSION_MAJOR" include/sparseir/version.h | awk '{print $3}')
-        MINOR=$(grep "#define SPARSEIR_VERSION_MINOR" include/sparseir/version.h | awk '{print $3}')
-        PATCH=$(grep "#define SPARSEIR_VERSION_PATCH" include/sparseir/version.h | awk '{print $3}')
-        VERSION="v${MAJOR}.${MINOR}.${PATCH}"
-        echo "version=$VERSION" >> "$GITHUB_OUTPUT"
-        echo "Version: $VERSION"
-
-        # Check if remote tag exists
-        git fetch --tags
-        if git tag -l | grep -q "^$VERSION$"; then
-          echo "Tag $VERSION already exists"
-          echo "should_create=false" >> "$GITHUB_OUTPUT"
-        else
-          echo "should_create=true" >> "$GITHUB_OUTPUT"
-        fi
-
-    - name: Create Release
-      if: steps.version.outputs.should_create == 'true'
-      uses: softprops/action-gh-release@v2
-      with:
-        tag_name: ${{ steps.version.outputs.version }}
-        name: Release ${{ steps.version.outputs.version }}
-        draft: false
-        prerelease: false
-        generate_release_notes: true
-      env:
-        GITHUB_TOKEN: ${{ secrets.DEPLOY }}
diff --git a/back/workflows/PublishPyPI.yml b/back/workflows/PublishPyPI.yml
deleted file mode 100644
index 6f4b2bf6..00000000
--- a/back/workflows/PublishPyPI.yml
+++ /dev/null
@@ -1,132 +0,0 @@
-name: Build & Publish
-
-on:
-  push:
-    tags: ["v*"]
-  workflow_dispatch:
-
-jobs:
-  build-wheels:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        include:
-          # Linux builds
-          - os: ubuntu-latest
-            cibw_archs: "auto"
-            deployment_target: ""
-            openblas_path: ""
-            py_tag: "cp310"
-          - os: ubuntu-latest
-            cibw_archs: "auto"
-            deployment_target: ""
-            openblas_path: ""
-            py_tag: "cp311"
-          - os: ubuntu-latest
-            cibw_archs: "auto"
-            deployment_target: ""
-            openblas_path: ""
-            py_tag: "cp312"
-          - os: ubuntu-latest
-            cibw_archs: "auto"
-            deployment_target: ""
-            openblas_path: ""
-            py_tag: "cp313"
-          # macOS Intel builds
-          - os: macos-13  # Intel Mac
-            cibw_archs: "x86_64"
-            deployment_target: "13.0"
-            openblas_path: "/usr/local/opt/openblas"
-            py_tag: "cp310"
-          - os: macos-13  # Intel Mac
-            cibw_archs: "x86_64"
-            deployment_target: "13.0"
-            openblas_path: "/usr/local/opt/openblas"
-            py_tag: "cp311"
-          - os: macos-13  # Intel Mac
-            cibw_archs: "x86_64"
-            deployment_target: "13.0"
-            openblas_path: "/usr/local/opt/openblas"
-            py_tag: "cp312"
-          - os: macos-13  # Intel Mac
-            cibw_archs: "x86_64"
-            deployment_target: "13.0"
-            openblas_path: "/usr/local/opt/openblas"
-            py_tag: "cp313"
-          # macOS Apple Silicon builds
-          - os: macos-latest  # Apple Silicon Mac
-            cibw_archs: "arm64"
-            deployment_target: "15.0"
-            openblas_path: "/opt/homebrew/opt/openblas"
-            py_tag: "cp310"
-          - os: macos-latest  # Apple Silicon Mac
-            cibw_archs: "arm64"
-            deployment_target: "15.0"
-            openblas_path: "/opt/homebrew/opt/openblas"
-            py_tag: "cp311"
-          - os: macos-latest  # Apple Silicon Mac
-            cibw_archs: "arm64"
-            deployment_target: "15.0"
-            openblas_path: "/opt/homebrew/opt/openblas"
-            py_tag: "cp312"
-          - os: macos-latest  # Apple Silicon Mac
-            cibw_archs: "arm64"
-            deployment_target: "15.0"
-            openblas_path: "/opt/homebrew/opt/openblas"
-            py_tag: "cp313"
-    steps:
-      - uses: actions/checkout@v5
-      - name: remove python/.gitignore
-        shell: bash
-        run: |
-          rm -f python/.gitignore
-      - name: prepare build
-        shell: bash
-        run: |
-          cd python
-          python prepare_build.py
-      - uses: pypa/cibuildwheel@v3.2.1
-        env:
-          CIBW_DEPENDENCY_VERSIONS: "latest"
-          CIBW_BUILD_VERBOSITY: 1
-          CIBW_MANYLINUX_X86_64_IMAGE: "manylinux_2_28"
-          CIBW_BUILD: "${{ matrix.py_tag }}-*"
-          CIBW_ENVIRONMENT_MACOS: "MACOSX_DEPLOYMENT_TARGET=${{ matrix.deployment_target || '11.0' }} SPARSEIR_USE_BLAS=1"
-          CIBW_ARCHS: ${{ matrix.cibw_archs }}
-          CIBW_SKIP: "*-manylinux_i686 *-musllinux_i686"
-          # Install OpenBLAS using micromamba (conda-forge) - separate for manylinux and musllinux
-          CIBW_BEFORE_ALL_MANYLINUX: "curl -Ls https://micro.mamba.pm/api/micromamba/linux-64/latest | tar -xvj bin/micromamba && ./bin/micromamba create -y -p /opt/openblas && ./bin/micromamba install -y -c conda-forge openblas -p /opt/openblas --no-deps"
-          CIBW_BEFORE_ALL_MUSLLINUX: "apk add --no-cache bzip2 && curl -Ls https://micro.mamba.pm/api/micromamba/linux-64/latest | tar -xvj bin/micromamba && ./bin/micromamba create -y -p /opt/openblas && ./bin/micromamba install -y -c conda-forge openblas -p /opt/openblas --no-deps"
-          CIBW_BEFORE_ALL_MACOS: "brew install openblas"
-          # Set environment variables to help CMake find OpenBLAS
-          CIBW_ENVIRONMENT_MANYLINUX: "SPARSEIR_USE_BLAS=1"
-          CIBW_ENVIRONMENT_MUSLLINUX: "SPARSEIR_USE_BLAS=1"
-        with:
-          package-dir: ./python
-          output-dir: dist
-      - uses: actions/upload-artifact@v5
-        with:
-          name: wheels-${{ matrix.os }}-${{ matrix.cibw_archs }}-${{ matrix.py_tag }}
-          path: dist/*
-
-  publish-pypi:
-    needs: build-wheels
-    runs-on: ubuntu-latest
-    environment:
-      name: pypi
-    permissions:
-      id-token: write     # Required for Trusted Publishing
-      contents: read
-    steps:
-      - uses: actions/download-artifact@v6
-        with:
-          path: dist
-          merge-multiple: true
-      - name: Publish to PyPI (Trusted)
-        uses: pypa/gh-action-pypi-publish@release/v1
-        with:
-          packages-dir: dist
-          repository-url: https://upload.pypi.org/legacy/
-          verbose: true
-          skip-existing: true
-          attestations: false  # Disable attestations due to Sigstore service issues
\ No newline at end of file
diff --git a/back/workflows/VersionConsistencyCheck.yml b/back/workflows/VersionConsistencyCheck.yml
deleted file mode 100644
index dd19f239..00000000
--- a/back/workflows/VersionConsistencyCheck.yml
+++ /dev/null
@@ -1,55 +0,0 @@
-name: Version Consistency Check
-
-on:
-  pull_request:
-    branches: [main]
-    paths:
-      - 'include/sparseir/version.h'
-      - 'python/pyproject.toml'
-      - 'update_version.py'
-  push:
-    branches: [main]
-    paths:
-      - 'include/sparseir/version.h'
-      - 'python/pyproject.toml'
-      - 'update_version.py'
-
-jobs:
-  check-version-consistency:
-    runs-on: ubuntu-latest
-    name: Check Version Consistency
-    
-    steps:
-    - name: Checkout code
-      uses: actions/checkout@v5
-      
-    - name: Set up Python
-      uses: actions/setup-python@v6
-      with:
-        python-version: '3.11'
-        
-    - name: Check version consistency
-      run: |
-        echo "🔍 Checking version consistency across components..."
-        echo "=================================================="
-        echo
-        
-        python update_version.py
-        exit_code=$?
-        
-        echo
-        if [ $exit_code -eq 0 ]; then
-          echo "✅ All versions are consistent and in sync!"
-          echo "   Ready for release process."
-        else
-          echo "❌ Version inconsistency detected!"
-          echo
-          echo "💡 To fix this issue:"
-          echo "   1. Run: python update_version.py <desired_version>"
-          echo "   2. Commit the changes: git add -A && git commit -m 'Fix version consistency'"
-          echo "   3. Push the changes to update this PR"
-          echo
-          echo "Example:"
-          echo "   python update_version.py 0.4.3"
-          exit 1
-        fi
\ No newline at end of file
diff --git a/back/workflows/conda.yml b/back/workflows/conda.yml
deleted file mode 100644
index 3cdc7b67..00000000
--- a/back/workflows/conda.yml
+++ /dev/null
@@ -1,40 +0,0 @@
-name: Build and upload conda packages
-
-# Triggered a new tag starting with "v" is pushed
-on:
-  push:
-    tags:
-      - 'v*'
-  workflow_dispatch:
-
-jobs:
-  build:
-    runs-on: ${{ matrix.runner_label }}
-    strategy:
-      matrix:
-        include:
-          - name: ubuntu-x64
-            runner_label: ubuntu-latest
-          - name: macos-arm64
-            runner_label: macos-latest
-
-    steps:
-    - uses: actions/checkout@v5
-    - uses: conda-incubator/setup-miniconda@v3
-      with:
-        auto-update-conda: true
-    - name: Conda info
-      shell: bash -el {0}
-      run: conda info
-    - name: Install dependencies
-      run: |
-        conda install conda-build anaconda-client -y
-
-    - name: Bulid and upload
-      working-directory: python
-      env:
-        ANACONDA_API_TOKEN: ${{secrets.ANACONDA_TOKEN}}
-      run: |
-        python3 --version
-        conda config --set anaconda_upload yes
-        conda build conda-recipe --user SpM-lab --output-folder conda-bld
diff --git a/build_capi_with_tests.sh b/build_capi_with_tests.sh
new file mode 100644
index 00000000..786c0272
--- /dev/null
+++ b/build_capi_with_tests.sh
@@ -0,0 +1,37 @@
+#!/bin/bash
+
+# Build backend/cxx and run C++ tests
+# Build directory: backend/cxx/build
+
+set -e  # Exit on error
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+echo -e "${GREEN}=== Building backend/cxx with tests ===${NC}"
+
+# Create build directory
+BUILD_DIR="backend/cxx/build"
+mkdir -p "$BUILD_DIR"
+
+# Configure CMake
+echo -e "${YELLOW}Configuring CMake...${NC}"
+cd "$BUILD_DIR"
+cmake ../.. \
+    -DCMAKE_BUILD_TYPE=Debug \
+    -DSPARSEIR_BUILD_TESTING=ON \
+    -DSPARSEIR_USE_BLAS=OFF
+
+# Build
+echo -e "${YELLOW}Building...${NC}"
+cmake --build . -j$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 4)
+
+# Run tests
+echo -e "${YELLOW}Running C++ tests...${NC}"
+ctest --output-on-failure --verbose
+
+echo -e "${GREEN}=== Build and test completed successfully ===${NC}"
+
diff --git a/sample_c/CMakeLists.txt b/capi_sample/CMakeLists.txt
similarity index 100%
rename from sample_c/CMakeLists.txt
rename to capi_sample/CMakeLists.txt
diff --git a/sample_c/README.md b/capi_sample/README.md
similarity index 62%
rename from sample_c/README.md
rename to capi_sample/README.md
index b304e992..2fc3d07c 100644
--- a/sample_c/README.md
+++ b/capi_sample/README.md
@@ -9,6 +9,9 @@
 
 
 ## Build and run
+
+### Option 1: Build with pre-installed library
+
 After installing the library, you can build the samples as follows:
 
 ```bash
@@ -16,4 +19,17 @@ After installing the library, you can build the samples as follows:
 export SparseIR_DIR=$HOME/opt/libsparseir/share/cmake
 cmake -S . -B ./build
 cmake --build build --target test
-```
\ No newline at end of file
+```
+
+### Option 2: Build C++ backend and samples together
+
+You can also build the C++ backend and run the samples in one go:
+
+```bash
+./run_sample.sh
+```
+
+This script will:
+1. Build the C++ backend with BLAS support in `work_cxx/` directory
+2. Install the backend to the `install/` subdirectory
+3. Build and run all sample programs
\ No newline at end of file
diff --git a/capi_sample/run_sample.sh b/capi_sample/run_sample.sh
new file mode 100755
index 00000000..9d6e65d7
--- /dev/null
+++ b/capi_sample/run_sample.sh
@@ -0,0 +1,55 @@
+#!/bin/bash
+
+# Build C++ backend with BLAS support and run samples
+# Build directory: work_cxx
+
+set -e  # Exit on error
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+echo -e "${GREEN}=== Building C++ backend with BLAS and running samples ===${NC}"
+
+# Create work_cxx directory structure
+BUILD_DIR="work_cxx"
+INSTALL_DIR="$BUILD_DIR/install"
+
+mkdir -p "$BUILD_DIR/build_backend"
+mkdir -p "$INSTALL_DIR"
+
+# Step 1: Build C++ backend with BLAS
+echo -e "${YELLOW}Building C++ backend with BLAS support...${NC}"
+cd "$BUILD_DIR/build_backend"
+
+cmake ../../../backend/cxx \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_INSTALL_PREFIX="../../work_cxx/install" \
+    -DSPARSEIR_USE_BLAS=ON \
+    -DSPARSEIR_BUILD_TESTING=OFF
+
+cmake --build . -j$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 4)
+cmake --install .
+
+cd ../..
+
+# Step 2: Set SparseIR_DIR to point to the installed backend
+export SparseIR_DIR="$(pwd)/work_cxx/install/share/cmake/SparseIR"
+
+# Clean build directory
+rm -rf ./build
+mkdir -p ./build
+
+echo -e "${YELLOW}Building samples...${NC}"
+cmake -S . -B ./build
+
+echo -e "${YELLOW}Building sample executables...${NC}"
+cmake --build build
+
+echo -e "${YELLOW}Running samples...${NC}"
+cmake --build build --target test
+
+echo -e "${GREEN}=== All samples completed successfully ===${NC}"
+
diff --git a/sample_c/sample1.c b/capi_sample/sample1.c
similarity index 98%
rename from sample_c/sample1.c
rename to capi_sample/sample1.c
index 99121e57..c64092e9 100644
--- a/sample_c/sample1.c
+++ b/capi_sample/sample1.c
@@ -33,7 +33,7 @@ assert(sve != NULL);
 // Create a fermionic finite temperature basis with pre-computed SVE result
 // Use SPIR_STATISTICS_BOSONIC for bosonic basis
 int max_size = -1;
-spir_basis* basis = spir_basis_new(SPIR_STATISTICS_FERMIONIC, beta, omega_max, kernel, sve, max_size, &status);
+spir_basis* basis = spir_basis_new(SPIR_STATISTICS_FERMIONIC, beta, omega_max, epsilon, kernel, sve, max_size, &status);
 assert(status == SPIR_COMPUTATION_SUCCESS);
 assert(basis != NULL);
 
diff --git a/sample_c/sample2.c b/capi_sample/sample2.c
similarity index 89%
rename from sample_c/sample2.c
rename to capi_sample/sample2.c
index 4c15720a..7fe4b4af 100644
--- a/sample_c/sample2.c
+++ b/capi_sample/sample2.c
@@ -32,11 +32,11 @@ assert(sve_logistic != NULL);
 
 // Create fermionic and bosonic finite temperature bases with pre-computed SVE result
 int max_size = -1;
-spir_basis* basis_fermionic = spir_basis_new(SPIR_STATISTICS_FERMIONIC, beta, omega_max, logistic_kernel, sve_logistic, max_size, &status);
+spir_basis* basis_fermionic = spir_basis_new(SPIR_STATISTICS_FERMIONIC, beta, omega_max, epsilon, logistic_kernel, sve_logistic, max_size, &status);
 assert(status == SPIR_COMPUTATION_SUCCESS);
 assert(basis_fermionic != NULL);
 
-spir_basis* basis_bosonic = spir_basis_new(SPIR_STATISTICS_BOSONIC, beta, omega_max, logistic_kernel, sve_logistic, max_size, &status);
+spir_basis* basis_bosonic = spir_basis_new(SPIR_STATISTICS_BOSONIC, beta, omega_max, epsilon, logistic_kernel, sve_logistic, max_size, &status);
 assert(status == SPIR_COMPUTATION_SUCCESS);
 assert(basis_bosonic != NULL);
 
@@ -49,7 +49,7 @@ spir_sve_result* sve_regularized = spir_sve_result_new(regularized_kernel, epsil
 assert(status == SPIR_COMPUTATION_SUCCESS);
 assert(sve_regularized != NULL);
 
-spir_basis* basis_regularized = spir_basis_new(SPIR_STATISTICS_BOSONIC, beta, omega_max, regularized_kernel, sve_regularized, max_size, &status);
+spir_basis* basis_regularized = spir_basis_new(SPIR_STATISTICS_BOSONIC, beta, omega_max, epsilon, regularized_kernel, sve_regularized, max_size, &status);
 assert(status == SPIR_COMPUTATION_SUCCESS);
 assert(basis_regularized != NULL);
 
diff --git a/sample_c/sample3.c b/capi_sample/sample3.c
similarity index 98%
rename from sample_c/sample3.c
rename to capi_sample/sample3.c
index 3bee9ea9..f8a683a2 100644
--- a/sample_c/sample3.c
+++ b/capi_sample/sample3.c
@@ -31,7 +31,7 @@ assert(sve_logistic != NULL);
 
 // Create fermionic and bosonic finite temperature bases with pre-computed SVE result
 int max_size = -1;
-spir_basis* basis = spir_basis_new(SPIR_STATISTICS_FERMIONIC, beta, omega_max, kernel, sve_logistic, max_size, &status);
+spir_basis* basis = spir_basis_new(SPIR_STATISTICS_FERMIONIC, beta, omega_max, epsilon, kernel, sve_logistic, max_size, &status);
 assert(status == SPIR_COMPUTATION_SUCCESS);
 assert(basis != NULL);
 
diff --git a/julia/README b/julia/README
new file mode 100644
index 00000000..e69de29b
diff --git a/julia/YggdrasilCommitHelper.jl/Yggdrasil b/julia/YggdrasilCommitHelper.jl/Yggdrasil
new file mode 160000
index 00000000..0d9490dd
--- /dev/null
+++ b/julia/YggdrasilCommitHelper.jl/Yggdrasil
@@ -0,0 +1 @@
+Subproject commit 0d9490dd112afba3df175acbb8d50fade7cc674b