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Lower DARPACK for small models #197

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Merged
zchlrnr merged 2 commits into from
Feb 15, 2026
+19 −2
Merged

Lower DARPACK for small models #197

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c8c363a
set DARPACK to zero for tiny models
Bruno02468 Feb 12, 2026
151e10d
Merge branch 'MYSTRANsolver:main' into main
Bruno02468 Feb 13, 2026
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21 changes: 19 additions & 2 deletions Source/LK4/EIG_LANCZOS_ARPACK.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,7 @@ SUBROUTINE EIG_LANCZOS_ARPACK
INTEGER(LONG) :: NUM_EST_EIGENS ! Number of estimated eigens in the freq interval (EIG_FRQ2 - EIG_FRQ1)
INTEGER(LONG) :: NUM_KMSM_DIAG_0 ! Number of zero diagonal terms in KMSM
INTEGER(LONG), PARAMETER :: SUBR_BEGEND = EIG_LANCZOS_ARPACK_BEGEND
INTEGER(LONG) :: MIN_NCV, MAX_NCV
INTEGER(LONG) :: MIN_NCV, MAX_NCV, LNONZEROS

REAL(DOUBLE) :: EPS1 ! A small number to compare zero to

Expand Down Expand Up @@ -295,10 +295,24 @@ SUBROUTINE EIG_LANCZOS_ARPACK

! Check that user did not ask for more than NDOFL-1 eigens (Lanczos can't be used to find all). If request is > NDOFL-1, decrease
! request to NDOFL-1 and give warning
IF (SOL_NAME(1:8) == 'BUCKLING') THEN
LNONZEROS = NDOFL - NUM_KLLD_DIAG_ZEROS
ELSE
LNONZEROS = NDOFL - NUM_MLL_DIAG_ZEROS
ENDIF


IF (NUM_EST_EIGENS > 0) THEN
NEV = NUM_EST_EIGENS + EIG_LANCZOS_NEV_DELT
ELSE
! prevent the addition of DARPACK from crashing ARPACK
IF ((EIG_N2 + DARPACK) > (LNONZEROS - 4)) THEN
WRITE(ERR,9775) NDOFL, DARPACK
IF (SUPWARN == 'N') THEN
WRITE(F06,9775) NDOFL, DARPACK
ENDIF
DARPACK = 0
END IF
NEV = EIG_N2 + DARPACK
ENDIF
IF (DEBUG(185) == 0) THEN ! If 0, only find finite eigens within the range requested
Expand All @@ -325,7 +339,7 @@ SUBROUTINE EIG_LANCZOS_ARPACK
ENDIF

MIN_NCV = NEV + 2
MAX_NCV = NDOFL - NUM_MLL_DIAG_ZEROS - 2
MAX_NCV = LNONZEROS - 2

! sanity check on feasible NCV range
IF (MIN_NCV > MAX_NCV) THEN
Expand Down Expand Up @@ -547,6 +561,9 @@ SUBROUTINE EIG_LANCZOS_ARPACK
' BEYOND THIS NUMBER' &
,/,14x,' (NOTE: USE OF BULK DATA PARAM ART_MASS WITH SMALL VALUE MAY ALLOW MGIV TO FIND MORE EIGENVALUES)')

9775 FORMAT(' *WARNING : DUE TO THE SIZE OF THE PROBLEM (NDOFL=',I0,'), PARAMETER DARPACK',/,15X,&
'WAS SET TO ZERO TO PREVENT ARPACK FROM CRASHING. ORIGINAL VALUE: ',I0)

9776 FORMAT(' *ERROR 9776: TOO MANY EIGENVALUES REQUESTED FOR THIS PROBLEM SIZE: NDOFL=',I0,', NEV=',I0,'.')

9777 FORMAT(' *ERROR 9777: UNABLE TO DETERMINE KRYLOV SUBSPACE SIZE NCV. NDOFL=',I0,', NEV=',I0,'.',/,15X,&
Expand Down