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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_max</h1>
<p>Atomically replace a value in FAM with the maximum of it and
some given value.</p>
<h2>Synopsis</h2>
<p class="code">void fam_max(Fam_Descriptor *descriptor, uint64_t offset,
int32_t value);</p>
<p class="code">void fam_max(Fam_Descriptor *descriptor, uint64_t offset,
int64_t value);</p>
<p class="code">void fam_max(Fam_Descriptor *descriptor, uint64_t offset,
uint32_t value);</p>
<p class="code">void fam_max(Fam_Descriptor *descriptor, uint64_t offset,
uint64_t value);</p>
<p class="code">void fam_max(Fam_Descriptor *descriptor, uint64_t offset, float
value);</p>
<p class="code">void fam_max(Fam_Descriptor *descriptor, uint64_t offset, double
value);</p>
<h2>Description</h2>
<p>These methods atomically replace a value in FAM with the maximum
of the value given and the existing 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 to the existing value at the given location.</td></tr>
</tbody>
</table>
<h2>Return Values</h2>
<p>None. 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_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>
</tbody></table>
<h2>Notes</h2>
<p>These methods atomically replace a value in FAM with the larger
of the existing value and the value given in the method, and return before the operation is complete. 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>
<p>Successful completion of a subsequent <code>fam_quiet()</code> call ensures the completion of this atomic operation.</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
// (an integer array with at least 10 elements)
Fam_Descriptor *descriptor = myFam->fam_lookup("myItem", "myRegion");
//Atomically set the maximum value for the first integer element in the array
myFam->fam_max(descriptor, 0, 100);
// ensure that the max operation is complete
myFam->fam_quiet();
// The first integer in FAM is now the maximum of its previous value and 100
} 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>