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<!DOCTYPE html>
<html lang="en">
<head>
<link rel="stylesheet" type="text/css" href="styles/style.css">
<title>OpenFAM: A library for programming Fabric-Attached Memory</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
<header>
<h1>OpenFAM Reference Implementation</h1>
</header>
<section>
<nav>
<ul>
<li><a href="index.html">Home</a></li>
<li><a href="release_notes.html">Release Notes</a></li>
<li><a href="limitations.html">Design Choices</a></li>
<li><a href="errors.html">Exceptions and Error Codes</a></li>
<li><a href="services.html">Services</a></li>
<li><a href="config_files.html">Configuration Files</a></li>
</ul>
<hr>
Initialization and Finalization
<ul>
<li><a href="fam_initialize.html">fam_initialize</a></li>
<li><a href="fam_finalize.html">fam_finalize</a></li>
<li><a href="fam_abort.html">fam_abort</a></li>
</ul>
<hr>
Options & Query
<ul>
<li><a href="fam_list_options.html">fam_list_options</a></li>
<li><a href="fam_get_option.html">fam_get_option</a></li>
<li><a href="fam_lookup.html">fam_lookup</a></li>
<li><a href="fam_stat.html">fam_stat</a></li>
</ul>
<hr>
Memory Allocation
<ul>
<li><a href="fam_create_region.html">fam_create_region</a></li>
<li><a href="fam_destroy_region.html">fam_destroy_region</a></li>
<li><a href="fam_resize_region.html">fam_resize_region</a></li>
<li><a href="fam_allocate.html">fam_allocate</a></li>
<li><a href="fam_deallocate.html">fam_deallocate</a></li>
<li><a href="fam_change_permissions.html">fam_change_permissions</a></li>
<li><a href="fam_close.html">fam_close</a></li>
</ul>
<hr>
Memory Map
<ul>
<li><a href="fam_map.html">fam_map</a></li>
<li><a href="fam_unmap.html">fam_unmap</a></li>
</ul>
<hr>
Data Path Operations
<ul>
<li><a href="fam_get.html">fam_get</a></li>
<li><a href="fam_put.html">fam_put</a></li>
<li><a href="fam_gather.html">fam_gather</a></li>
<li><a href="fam_scatter.html">fam_scatter</a></li>
<li><a href="fam_copy.html">fam_copy</a></li>
<li><a href="fam_copy_wait.html">fam_copy_wait</a></li>
<li><a href="fam_backup.html">fam_backup</a></li>
<li><a href="fam_backup_wait.html">fam_backup_wait</a></li>
<li><a href="fam_restore.html">fam_restore</a></li>
<li><a href="fam_restore_wait.html">fam_restore_wait</a></li>
<li><a href="fam_delete_backup.html">fam_delete_backup</a></li>
<li><a href="fam_delete_backup_wait.html">fam_delete_backup_wait</a></li>
</ul>
<hr>
Atomics
<ul>
<li><a href="fam_set.html">fam_set</a></li>
<li><a href="fam_add.html">fam_add</a></li>
<li><a href="fam_subtract.html">fam_subtract</a></li>
<li><a href="fam_min.html">fam_min</a></li>
<li><a href="fam_max.html">fam_max</a></li>
<li><a href="fam_and.html">fam_and</a></li>
<li><a href="fam_or.html">fam_or</a></li>
<li><a href="fam_xor.html">fam_xor</a></li>
<li><a href="fam_fetch_TYPE.html">fam_fetch_TYPE</a></li>
<li><a href="fam_swap.html">fam_swap</a></li>
<li><a href="fam_compare_swap.html">fam_compare_swap</a></li>
<li><a href="fam_fetch_add.html">fam_fetch_add</a></li>
<li><a href="fam_fetch_subtract.html">fam_fetch_subtract</a></li>
<li><a href="fam_fetch_min.html">fam_fetch_min</a></li>
<li><a href="fam_fetch_and.html">fam_fetch_and</a></li>
<li><a href="fam_fetch_max.html">fam_fetch_max</a></li>
<li><a href="fam_fetch_or.html">fam_fetch_or</a></li>
<li><a href="fam_fetch_xor.html">fam_fetch_xor</a></li>
</ul>
<hr>
Ordering
<ul>
<li><a href="fam_barrier_all.html">fam_barrier_all</a></li>
<li><a href="fam_fence.html">fam_fence</a></li>
<li><a href="fam_quiet.html">fam_quiet</a></li>
<li><a href="fam_progress.html">fam_progress</a></li>
<li><a href="fam_context_open.html">fam_context_open</a></li>
<li><a href="fam_context_close.html">fam_context_close</a></li>
</ul>
<hr>
</nav>
<article>
<h1 class="code">openfam::fam::fam_fetch_max</h1>
<p>Atomically replaces a value in FAM with the
larger of the value in FAM and a given value, and returns the old
value.</p>
<h2>Synopsis</h2>
<p class="code">int32_t fam_fetch_max(Fam_Descriptor *descriptor, uint64_t offset, int32_t value);<br>
int64_t fam_fetch_max(Fam_Descriptor *descriptor, uint64_t offset, int64_t value);<br>
uint32_t fam_fetch_max(Fam_Descriptor *descriptor, uint64_t offset, uint32_t value);<br>
uint64_t fam_fetch_max(Fam_Descriptor *descriptor, uint64_t offset, uint64_t value);<br>
float fam_fetch_max(Fam_Descriptor *descriptor, uint64_t offset, float value);<br>
double fam_fetch_max(Fam_Descriptor *descriptor, uint64_t offset, double value);</p>
<h2>Description</h2>
<p>These methods atomically replace a value in
FAM with the larger of the value in FAM and the given value, and
return the old value.</p>
<h2>Input Arguments</h2>
<table>
<tbody>
<tr><th>Name</th><th>Description</th></tr>
<tr><td class="code">descriptor</td><td>Descriptor associated with the data item.</td></tr>
<tr><td class="code">offset</td><td>Offset within the data item in FAM where value is located.</td></tr>
<tr><td class="code">value</td><td>Value to be compared the existing value at the given location.</td></tr>
</tbody>
</table>
<h2>Return Values</h2>
<p>The original value from FAM. Throws
<code>Fam_Exception</code> on error.</p>
<h2>Fam Error Numbers</h2>
<table><tbody>
<tr><th>Error</th><th>Description</th></tr>
<tr><td class="code">FAM_ERR_INVALID</td><td>API called with incorrect parameters.</td></tr>
<tr><td class="code">FAM_ERR_NOPERM</td><td>Caller does not have access rights.</td></tr>
<tr><td class="code">FAM_ERR_LIBFABRIC</td><td>libfabric error occurred.</td></tr>
<tr><td class="code">FAM_ERR_NOTFOUND</td><td>Item not found in the region.</td></tr>
<tr><td class="code">FAM_ERR_RPC</td><td>Communication error from grpc layer.</td></tr>
<tr><td class="code">FAM_ERR_RPC_CLIENT_NOTFOUND</td><td>RPC service not available.</td></tr>
<tr><td class="code">FAM_ERR_METADATA</td><td>Metadata service error.</td></tr>
<tr><td class="code">FAM_ERR_MEMORY</td><td>Memory service error.</td></tr>
<tr><td class="code">FAM_ERR_RESOURCE</td><td>Resource not available.</td></tr>
<tr><td class="code">FAM_ERR_TIMEOUT</td><td>Number of libfabric retry count reached.</td></tr>
</tbody></table>
<h2>Notes</h2>
<p>These methods atomically replace a value in
FAM with the maximum of that value and a given value. The old value is
returned. Note that the offset argument must point to the correct
value for the data type. Availability of these methods is dependent on
hardware support for the operations.</p>
<h2>Example</h2>
<pre>
#include <string.h>
#include <fam/fam.h>
#include <fam/fam_exception.h>
using namespace std;
using namespace openfam;
int main(void) {
fam *myFam = new fam();
// ... Initialization code here
try {
// look up the descriptor to a previously allocated data item
Fam_Descriptor *descriptor = myFam->fam_lookup("myItem", "myRegion");
// Atomically replace the first element of the array with the larger of the current
// value and 10, and return the old value
uint32_t oldValue = myFam->fam_fetch_max(descriptor, 0, 10);
// The first integer in FAM is the larger of 10 and the previous value, and the old value is returned
// ... subsequent code here
} catch (Fam_Exception &e) {
printf("fam API failed: %d: %s\n", e.fam_error(), e.fam_error_msg());
}
// ... Finalization code follows
}
</pre>
</article>
</section>
<footer>
<p>Copyright 2021-23, Hewlett Packard Enterprise Development Co, LLP</p>
</footer>
</body>
</html>