deploy: ef39882fa1e13740d2530c7a0637bd1f1a822b68

author: byrnHDF <byrnHDF@users.noreply.github.com> 2023-11-16 13:49:28 (GMT)
committer: byrnHDF <byrnHDF@users.noreply.github.com> 2023-11-16 13:49:28 (GMT)
commit: 4f20d880c97be1249f8d89ced95f72836dbf3ee0 (patch)
tree: 30d8dcb282134b7126b092796f2be00d2d97bd3c /develop/group___p_h5_f.html
parent: 4e7e457497c948b41c8b0065225875bf10cdf9d4 (diff)
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+   &#160;<span id="projectnumber">1.15.0.ef39882</span>
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+   <div id="projectbrief">API Reference</div>
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+<div class="header">
+  <div class="summary">
+<a href="#func-members">Functions</a>  </div>
+  <div class="headertitle">
+<div class="title">Parallel<div class="ingroups"><a class="el" href="group___h5_f.html">Files (H5F)</a></div></div>  </div>
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+<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
+<div id="dynsection-0" onclick="return toggleVisibility(this)" class="dynheader closed" style="cursor:pointer;">
+  <img id="dynsection-0-trigger" src="closed.png" alt="+"/> Collaboration diagram for Parallel:</div>
+<div id="dynsection-0-summary" class="dynsummary" style="display:block;">
+</div>
+<div id="dynsection-0-content" class="dyncontent" style="display:none;">
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+</div>
+<table class="memberdecls">
+<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
+Functions</h2></td></tr>
+<tr class="memitem:ga087dbbf37cb5c451ae8a6f66b227f0fc"><td class="memItemLeft" align="right" valign="top"><a class="el" href="_h5public_8h.html#a3b079ecf932a5c599499cf7e298af160">herr_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc">H5Fset_mpi_atomicity</a> (<a class="el" href="_h5_ipublic_8h.html#a0045db7ff9c22ad35db6ae91662e1943">hid_t</a> file_id, <a class="el" href="_h5public_8h.html#ad470b00eccd2115c707c02de5fa1120d">hbool_t</a> flag)</td></tr>
+<tr class="memdesc:ga087dbbf37cb5c451ae8a6f66b227f0fc"><td class="mdescLeft">&#160;</td><td class="mdescRight">Sets the MPI atomicity mode.  <a href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc">More...</a><br /></td></tr>
+<tr class="separator:ga087dbbf37cb5c451ae8a6f66b227f0fc"><td class="memSeparator" colspan="2">&#160;</td></tr>
+<tr class="memitem:ga849316b77788799fecb321a87d987ade"><td class="memItemLeft" align="right" valign="top"><a class="el" href="_h5public_8h.html#a3b079ecf932a5c599499cf7e298af160">herr_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___p_h5_f.html#ga849316b77788799fecb321a87d987ade">H5Fget_mpi_atomicity</a> (<a class="el" href="_h5_ipublic_8h.html#a0045db7ff9c22ad35db6ae91662e1943">hid_t</a> file_id, <a class="el" href="_h5public_8h.html#ad470b00eccd2115c707c02de5fa1120d">hbool_t</a> *flag)</td></tr>
+<tr class="memdesc:ga849316b77788799fecb321a87d987ade"><td class="mdescLeft">&#160;</td><td class="mdescRight">Retrieves the atomicity mode in use.  <a href="group___p_h5_f.html#ga849316b77788799fecb321a87d987ade">More...</a><br /></td></tr>
+<tr class="separator:ga849316b77788799fecb321a87d987ade"><td class="memSeparator" colspan="2">&#160;</td></tr>
+</table>
+<h2 class="groupheader">Function Documentation</h2>
+<a id="ga849316b77788799fecb321a87d987ade"></a>
+<h2 class="memtitle"><span class="permalink"><a href="#ga849316b77788799fecb321a87d987ade">&#9670;&nbsp;</a></span>H5Fget_mpi_atomicity()</h2>
+
+<div class="memitem">
+<div class="memproto">
+      <table class="memname">
+        <tr>
+          <td class="memname"><a class="el" href="_h5public_8h.html#a3b079ecf932a5c599499cf7e298af160">herr_t</a> H5Fget_mpi_atomicity </td>
+          <td>(</td>
+          <td class="paramtype"><a class="el" href="_h5_ipublic_8h.html#a0045db7ff9c22ad35db6ae91662e1943">hid_t</a>&#160;</td>
+          <td class="paramname"><em>file_id</em>, </td>
+        </tr>
+        <tr>
+          <td class="paramkey"></td>
+          <td></td>
+          <td class="paramtype"><a class="el" href="_h5public_8h.html#ad470b00eccd2115c707c02de5fa1120d">hbool_t</a> *&#160;</td>
+          <td class="paramname"><em>flag</em>&#160;</td>
+        </tr>
+        <tr>
+          <td></td>
+          <td>)</td>
+          <td></td><td></td>
+        </tr>
+      </table>
+</div><div class="memdoc">
+
+<p>Retrieves the atomicity mode in use. </p>
+<dl class="params"><dt>Parameters</dt><dd>
+  <table class="params">
+    <tr><td class="paramdir">[in]</td><td class="paramname">file_id</td><td>File identifier </td></tr>
+    <tr><td class="paramdir">[out]</td><td class="paramname">flag</td><td>Logical flag for atomicity setting. Valid values are: <ul>
+<li>1 &ndash; MPI file access is set to atomic mode. </li>
+<li>0 &ndash; MPI file access is set to nonatomic mode. </li>
+</ul>
+</td></tr>
+  </table>
+  </dd>
+</dl>
+<dl class="section return"><dt>Returns</dt><dd>Returns a non-negative value if successful; otherwise, returns a negative value.</dd></dl>
+<p><a class="el" href="group___p_h5_f.html#ga849316b77788799fecb321a87d987ade" title="Retrieves the atomicity mode in use.">H5Fget_mpi_atomicity()</a> retrieves the current consistency semantics mode for data access for the file <code>file_id</code>.</p>
+<p>Upon successful return, <code>flag</code> will be set to <code>1</code> if file access is set to atomic mode and <code>0</code> if file access is set to nonatomic mode.</p>
+<dl class="section see"><dt>See also</dt><dd><a href="https://portal.hdfgroup.org/display/HDF5/Enabling+a+Strict+Consistency+Semantics+Model+in+Parallel+HDF5">Enabling a Strict Consistency Semantics Model in Parallel HDF5</a></dd></dl>
+<dl class="section since"><dt>Since</dt><dd>1.8.9 </dd></dl>
+
+</div>
+</div>
+<a id="ga087dbbf37cb5c451ae8a6f66b227f0fc"></a>
+<h2 class="memtitle"><span class="permalink"><a href="#ga087dbbf37cb5c451ae8a6f66b227f0fc">&#9670;&nbsp;</a></span>H5Fset_mpi_atomicity()</h2>
+
+<div class="memitem">
+<div class="memproto">
+      <table class="memname">
+        <tr>
+          <td class="memname"><a class="el" href="_h5public_8h.html#a3b079ecf932a5c599499cf7e298af160">herr_t</a> H5Fset_mpi_atomicity </td>
+          <td>(</td>
+          <td class="paramtype"><a class="el" href="_h5_ipublic_8h.html#a0045db7ff9c22ad35db6ae91662e1943">hid_t</a>&#160;</td>
+          <td class="paramname"><em>file_id</em>, </td>
+        </tr>
+        <tr>
+          <td class="paramkey"></td>
+          <td></td>
+          <td class="paramtype"><a class="el" href="_h5public_8h.html#ad470b00eccd2115c707c02de5fa1120d">hbool_t</a>&#160;</td>
+          <td class="paramname"><em>flag</em>&#160;</td>
+        </tr>
+        <tr>
+          <td></td>
+          <td>)</td>
+          <td></td><td></td>
+        </tr>
+      </table>
+</div><div class="memdoc">
+
+<p>Sets the MPI atomicity mode. </p>
+<dl class="params"><dt>Parameters</dt><dd>
+  <table class="params">
+    <tr><td class="paramdir">[in]</td><td class="paramname">file_id</td><td>File identifier </td></tr>
+    <tr><td class="paramdir">[in]</td><td class="paramname">flag</td><td>Logical flag for atomicity setting. Valid values are: <ul>
+<li><code>1</code> &ndash; Sets MPI file access to atomic mode. </li>
+<li><code>0</code> &ndash; Sets MPI file access to nonatomic mode. </li>
+</ul>
+</td></tr>
+  </table>
+  </dd>
+</dl>
+<dl class="section return"><dt>Returns</dt><dd>Returns a non-negative value if successful; otherwise, returns a negative value.</dd></dl>
+<dl class="section user"><dt>Motivation</dt><dd><a class="el" href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc" title="Sets the MPI atomicity mode.">H5Fset_mpi_atomicity()</a> is applicable only in parallel environments using MPI I/O. The function is one of the tools used to ensure sequential consistency. This means that a set of operations will behave as though they were performed in a serial order consistent with the program order.</dd></dl>
+<p><a class="el" href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc" title="Sets the MPI atomicity mode.">H5Fset_mpi_atomicity()</a> sets MPI consistency semantics for data access to the file, <code>file_id</code>.</p>
+<p>If <code>flag</code> is set to <code>1</code>, all file access operations will appear atomic, guaranteeing sequential consistency. If <code>flag</code> is set to <code>0</code>, enforcement of atomic file access will be turned off.</p>
+<p><a class="el" href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc" title="Sets the MPI atomicity mode.">H5Fset_mpi_atomicity()</a> is a collective function and all participating processes must pass the same values for <code>file_id</code> and <code>flag</code>.</p>
+<p>This function is available only when the HDF5 library is configured with parallel support (<code>&ndash;enable-parallel | HDF5_ENABLE_PARALLEL</code>). It is useful only when used with the <a class="el" href="_h5_f_dmpio_8h.html#a7a231bc1d78744088a4e1d297284cabf">H5FD_MPIO</a> driver (see <a class="el" href="group___f_a_p_l.html#gaa0204810c1fea1667d62cf7c176416ff" title="Stores MPI IO communicator information to the file access property list.">H5Pset_fapl_mpio()</a>). </p>
+<dl class="section attention"><dt>Attention</dt><dd><p class="startdd"><a class="el" href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc" title="Sets the MPI atomicity mode.">H5Fset_mpi_atomicity()</a> calls <code>MPI_File_set_atomicity</code> underneath and is not supported if the execution platform does not support <code>MPI_File_set_atomicity</code>. When it is supported and used, the performance of data access operations may drop significantly.</p>
+<p class="enddd">In certain scenarios, even when <code>MPI_File_set_atomicity</code> is supported, setting atomicity with <a class="el" href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc" title="Sets the MPI atomicity mode.">H5Fset_mpi_atomicity()</a> and <code>flag</code> set to 1 does not always yield strictly atomic updates. For example, some <a class="el" href="group___h5_d.html#ga98f44998b67587662af8b0d8a0a75906" title="Writes raw data from a buffer to a dataset.">H5Dwrite()</a> calls translate to multiple <code>MPI_File_write_at</code> calls. This happens in all cases where the high-level file access routine translates to multiple lower level file access routines. The following scenarios will raise this issue: </p><ul>
+<li>Non-contiguous file access using independent I/O </li>
+<li>Partial collective I/O using chunked access </li>
+<li>Collective I/O using filters or when data conversion is required</li>
+</ul>
+<p>This issue arises because MPI atomicity is a matter of MPI file access operations rather than HDF5 access operations. But the user is normally seeking atomicity at the HDF5 level. To accomplish this, the application must set a barrier after a write, <a class="el" href="group___h5_d.html#ga98f44998b67587662af8b0d8a0a75906" title="Writes raw data from a buffer to a dataset.">H5Dwrite()</a>, but before the next read, <a class="el" href="group___h5_d.html#ga8287d5a7be7b8e55ffeff68f7d26811c" title="Reads raw data from a dataset into a provided buffer.">H5Dread()</a>, in addition to calling <a class="el" href="group___p_h5_f.html#ga087dbbf37cb5c451ae8a6f66b227f0fc" title="Sets the MPI atomicity mode.">H5Fset_mpi_atomicity()</a>.The barrier will guarantee that all underlying write operations execute atomically before the read operations starts. This ensures additional ordering semantics and will normally produce the desired behavior. </p>
+</dd></dl>
+<dl class="section see"><dt>See also</dt><dd><a href="https://portal.hdfgroup.org/display/HDF5/Enabling+a+Strict+Consistency+Semantics+Model+in+Parallel+HDF5">Enabling a Strict Consistency Semantics Model in Parallel HDF5</a></dd></dl>
+<dl class="section since"><dt>Since</dt><dd>1.8.9 </dd></dl>
+
+</div>
+</div>
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author	byrnHDF <byrnHDF@users.noreply.github.com>	2023-11-16 13:49:28 (GMT)
committer	byrnHDF <byrnHDF@users.noreply.github.com>	2023-11-16 13:49:28 (GMT)
commit	4f20d880c97be1249f8d89ced95f72836dbf3ee0 (patch)
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