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420 lines
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420 lines
21 KiB
HTML
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<head><title>psb_cdall — Allocates a communication descriptor</title>
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<!--l. 8--><div class="crosslinks"><p class="noindent">[<a
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href="userhtmlsu34.html" >next</a>] [<a
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href="userhtmlsu28.html#tailuserhtmlsu30.html">tail</a>] [<a
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href="userhtmlsu32.html#userhtmlsu33.html" >up</a>] </p></div>
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<h4 class="subsectionHead"><span class="titlemark">6.1 </span> <a
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id="x41-780006.1"></a>psb_cdall — Allocates a communication descriptor</h4>
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<pre class="verbatim" id="verbatim-33">
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call psb_cdall(icontxt, desc_a, info,mg=mg,parts=parts)
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call psb_cdall(icontxt, desc_a, info,vg=vg,[mg=mg,flag=flag])
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call psb_cdall(icontxt, desc_a, info,vl=vl,[nl=nl,globalcheck=.false.,lidx=lidx])
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call psb_cdall(icontxt, desc_a, info,nl=nl)
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call psb_cdall(icontxt, desc_a, info,mg=mg,repl=.true.)
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</pre>
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<!--l. 16--><p class="nopar" >
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<!--l. 18--><p class="indent" > This subroutine initializes the communication descriptor associated with an index
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space. One of the optional arguments <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">parts</span></span></span>, <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vg</span></span></span>, <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl</span></span></span>, <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">nl</span></span></span> or <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">repl</span></span></span> must be specified,
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thereby choosing the specific initialization strategy.
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<dl class="description"><dt class="description">
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<span
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class="cmbx-10">On Entry</span> </dt><dd
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class="description">
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</dd><dt class="description">
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<span
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class="cmbx-10">Type:</span> </dt><dd
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class="description">Synchronous.
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</dd><dt class="description">
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<span
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class="cmbx-10">icontxt</span> </dt><dd
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class="description">the communication context.<br
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class="newline" />Scope:<span
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class="cmbx-10">global</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">required</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: an integer value.
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</dd><dt class="description">
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<span
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class="cmbx-10">vg</span> </dt><dd
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class="description">Data allocation: each index <span
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class="cmmi-10">i </span><span
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class="cmsy-10">∈{</span>1<span
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class="cmmi-10">…</span><span
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class="cmmi-10">mg</span><span
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class="cmsy-10">} </span>is allocated to process <span
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class="cmmi-10">vg</span>(<span
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class="cmmi-10">i</span>).<br
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class="newline" />Scope:<span
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class="cmbx-10">global</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: an integer array.
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</dd><dt class="description">
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<span
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class="cmbx-10">flag</span> </dt><dd
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class="description">Specifies whether entries in <span
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class="cmmi-10">vg </span>are zero- or one-based.<br
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class="newline" />Scope:<span
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class="cmbx-10">global</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: an integer value 0<span
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class="cmmi-10">,</span>1, default 0.
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</dd><dt class="description">
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<span
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class="cmbx-10">mg</span> </dt><dd
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class="description">the (global) number of rows of the problem.<br
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class="newline" />Scope:<span
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class="cmbx-10">global</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: an integer value. It is required if <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">parts</span></span></span> or <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">repl</span></span></span> is specified,
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it is optional if <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vg</span></span></span> is specified.
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</dd><dt class="description">
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<span
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class="cmbx-10">parts</span> </dt><dd
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class="description">the subroutine that defines the partitioning scheme.<br
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class="newline" />Scope:<span
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class="cmbx-10">global</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">required</span>.<br
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class="newline" />Specified as: a subroutine.
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</dd><dt class="description">
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<span
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class="cmbx-10">vl</span> </dt><dd
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class="description">Data allocation: the set of global indices <span
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class="cmmi-10">vl</span>(1 : <span
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class="cmmi-10">nl</span>) belonging to the calling
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process. <br
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class="newline" />Scope:<span
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class="cmbx-10">local</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: an integer array.
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</dd><dt class="description">
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<span
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class="cmbx-10">nl</span> </dt><dd
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class="description">Data allocation: in a generalized block-row distribution the number of indices
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belonging to the current process. <br
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class="newline" />Scope:<span
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class="cmbx-10">local</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: an integer value. May be specified together with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl</span></span></span>.
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</dd><dt class="description">
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<span
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class="cmbx-10">repl</span> </dt><dd
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class="description">Data allocation: build a replicated index space (i.e. all processes own all
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indices).<br
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class="newline" />Scope:<span
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class="cmbx-10">global</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: the logical value <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">.true.</span></span></span>
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</dd><dt class="description">
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<span
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class="cmbx-10">globalcheck</span> </dt><dd
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class="description">Data allocation: do global checks on the local index lists <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl</span></span></span><br
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class="newline" />Scope:<span
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class="cmbx-10">global</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: a logical value, default: <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">.false.</span></span></span>
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</dd><dt class="description">
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<span
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class="cmbx-10">lidx</span> </dt><dd
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class="description">Data allocation: the set of local indices <span
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class="cmmi-10">lidx</span>(1 : <span
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class="cmmi-10">nl</span>) to be assigned to the
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global indices <span
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class="cmmi-10">vl</span>. <br
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class="newline" />Scope:<span
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class="cmbx-10">local</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">optional</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">in</span>.<br
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class="newline" />Specified as: an integer array.</dd></dl>
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<!--l. 86--><p class="indent" >
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<dl class="description"><dt class="description">
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<span
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class="cmbx-10">On Return</span> </dt><dd
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class="description">
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</dd><dt class="description">
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<span
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class="cmbx-10">desc</span><span
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class="cmbx-10">_a</span> </dt><dd
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class="description">the communication descriptor.<br
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class="newline" />Scope:<span
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class="cmbx-10">local</span>.<br
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class="newline" />Type:<span
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class="cmbx-10">required</span>.<br
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class="newline" />Intent: <span
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class="cmbx-10">out</span>.<br
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class="newline" />Specified as: a structured data of type <a
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href="userhtmlsu5.html#descdata"><span
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class="cmtt-10">psb</span><span
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class="cmtt-10">_desc</span><span
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class="cmtt-10">_type</span></a>.
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</dd><dt class="description">
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<span
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class="cmbx-10">info</span> </dt><dd
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class="description">Error code.<br
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class="newline" />Scope: <span
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class="cmbx-10">local </span><br
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class="newline" />Type: <span
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class="cmbx-10">required </span><br
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class="newline" />Intent: <span
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class="cmbx-10">out</span>.<br
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class="newline" />An integer value; 0 means no error has been detected.</dd></dl>
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<!--l. 100--><p class="noindent" ><span
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class="cmbx-12">Notes</span>
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<ol class="enumerate1" >
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<li
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class="enumerate" id="x41-78002x1">One of the optional arguments <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">parts</span></span></span>, <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vg</span></span></span>, <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl</span></span></span>, <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">nl</span></span></span> or <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">repl</span></span></span> must be specified,
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thereby choosing the initialization strategy as follows:
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<dl class="description"><dt class="description">
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<span
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class="cmbx-10">parts</span> </dt><dd
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class="description">In this case we have a subroutine specifying the mapping between global
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indices and process/local index pairs. If this optional argument is
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specified, then it is mandatory to specify the argument <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">mg</span></span></span> as well. The
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subroutine must conform to the following interface:
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<pre class="verbatim" id="verbatim-34">
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  interface
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     subroutine psb_parts(glob_index,mg,np,pv,nv)
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       integer, intent (in)  :: glob_index,np,mg
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       integer, intent (out) :: nv, pv(*)
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     end subroutine psb_parts
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  end interface
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</pre>
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<!--l. 118--><p class="nopar" > The input arguments are:
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<dl class="description"><dt class="description">
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<span
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class="cmbx-10">glob</span><span
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class="cmbx-10">_index</span> </dt><dd
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class="description">The global index to be mapped;
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</dd><dt class="description">
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<span
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class="cmbx-10">np</span> </dt><dd
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class="description">The number of processes in the mapping;
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</dd><dt class="description">
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<span
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class="cmbx-10">mg</span> </dt><dd
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class="description">The total number of global rows in the mapping;</dd></dl>
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<!--l. 125--><p class="noindent" >The output arguments are:
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<dl class="description"><dt class="description">
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<span
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class="cmbx-10">nv</span> </dt><dd
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class="description">The number of entries in <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">pv</span></span></span>;
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</dd><dt class="description">
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<span
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class="cmbx-10">pv</span> </dt><dd
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class="description">A vector containing the indices of the processes to which the
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global index should be assigend; each entry must satisfy 0 <span
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class="cmsy-10">≤</span>
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<span
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class="cmmi-10">pv</span>(<span
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class="cmmi-10">i</span>) <span
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class="cmmi-10">< np</span>; if <span
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class="cmmi-10">nv > </span>1 we have an index assigned to multiple
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processes, i.e. we have an overlap among the subdomains.</dd></dl>
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</dd><dt class="description">
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<span
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class="cmbx-10">vg</span> </dt><dd
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class="description">In this case the association between an index and a process is specified via
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an integer vector <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vg(1:mg)</span></span></span>; each index <span
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class="cmmi-10">i </span><span
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class="cmsy-10">∈{</span>1<span
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class="cmmi-10">…</span><span
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class="cmmi-10">mg</span><span
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class="cmsy-10">} </span>is assigned to process
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<span
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class="cmmi-10">vg</span>(<span
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class="cmmi-10">i</span>). The vector <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vg</span></span></span> must be identical on all calling processes; its
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entries may have the ranges (0<span
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class="cmmi-10">…</span><span
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class="cmmi-10">np </span><span
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class="cmsy-10">- </span>1) or (1<span
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class="cmmi-10">…</span><span
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class="cmmi-10">np</span>) according to the
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value of <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">flag</span></span></span>. The size <span
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class="cmmi-10">mg </span>may be specified via the optional
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argument <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">mg</span></span></span>; the default is to use the entire vector <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vg</span></span></span>, thus having
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<span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">mg=size(vg)</span></span></span>.
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</dd><dt class="description">
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<span
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class="cmbx-10">vl</span> </dt><dd
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class="description">In this case we are specifying the list of indices <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl(1:nl)</span></span></span> assigned to the
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current process; thus, the global problem size <span
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class="cmmi-10">mg </span>is given by the range of
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the aggregate of the individual vectors <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl</span></span></span> specified in the calling
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processes. The size may be specified via the optional argument <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">nl</span></span></span>; the
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default is to use the entire vector <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl</span></span></span>, thus having <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">nl=size(vl)</span></span></span>. If
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<span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">globalcheck=.true.</span></span></span> the subroutine will check how many times each
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entry in the global index space (1<span
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class="cmmi-10">…</span><span
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class="cmmi-10">mg</span>) is specified in the input lists <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">vl</span></span></span>,
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thus allowing for the presence of overlap in the input, and checking for
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“orphan” indices. If <span class="obeylines-h"><span class="verb"><span
|
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class="cmtt-10">globalcheck=.false.</span></span></span>, the subroutine will not
|
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check for overlap, and may be significantly faster, but the user is
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implicitly guaranteeing that there are neither orphan nor overlap
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indices.
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</dd><dt class="description">
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<span
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class="cmbx-10">lidx</span> </dt><dd
|
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class="description">The optional argument <span class="obeylines-h"><span class="verb"><span
|
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class="cmtt-10">lidx</span></span></span> is available for those cases in which the user
|
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has already established a global-to-local mapping; if it is specified, each
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index in <span class="obeylines-h"><span class="verb"><span
|
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class="cmtt-10">vl(i)</span></span></span> will be mapped to the corresponding local index <span class="obeylines-h"><span class="verb"><span
|
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class="cmtt-10">lidx(i)</span></span></span>.
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When specifying the argument <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">lidx</span></span></span> the user would also likely employ
|
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<span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">lidx</span></span></span> in calls to <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_cdins</span></span></span> and <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">local</span></span></span> in calls to <span class="obeylines-h"><span class="verb"><span
|
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class="cmtt-10">psb_spins</span></span></span> and
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<span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_geins</span></span></span>; see also sec. <a
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href="userhtmlsu3.html#x9-70002.3.1">2.3.1<!--tex4ht:ref: sec:usermaps --></a>.
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</dd><dt class="description">
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<span
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class="cmbx-10">nl</span> </dt><dd
|
|
class="description">If this argument is specified alone (i.e. without <span class="obeylines-h"><span class="verb"><span
|
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class="cmtt-10">vl</span></span></span>) the result is a
|
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generalized row-block distribution in which each process <span
|
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class="cmmi-10">I </span>gets assigned a
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consecutive chunk of <span
|
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class="cmmi-10">N</span><sub><span
|
|
class="cmmi-7">I</span></sub> = <span
|
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class="cmmi-10">nl </span>global indices.
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</dd><dt class="description">
|
|
<span
|
|
class="cmbx-10">repl</span> </dt><dd
|
|
class="description">This arguments specifies to replicate all indices on all processes. This is a
|
|
special purpose data allocation that is useful in the construction of some
|
|
multilevel preconditioners.</dd></dl>
|
|
</li>
|
|
<li
|
|
class="enumerate" id="x41-78004x2">On exit from this routine the descriptor is in the build state.
|
|
</li>
|
|
<li
|
|
class="enumerate" id="x41-78006x3">Calling the routine with <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">vg</span></span></span> or <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">parts</span></span></span> implies that every process will scan the
|
|
entire index space to figure out the local indices.
|
|
</li>
|
|
<li
|
|
class="enumerate" id="x41-78008x4">Overlapped indices are possible with both <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">parts</span></span></span> and <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">vl</span></span></span> invocations.
|
|
</li>
|
|
<li
|
|
class="enumerate" id="x41-78010x5">When the subroutine is invoked with <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">vl</span></span></span> in conjunction with <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">globalcheck=.true.</span></span></span>,
|
|
it will perform a scan of the index space to search for overlap or orphan
|
|
indices.
|
|
</li>
|
|
<li
|
|
class="enumerate" id="x41-78012x6">When the subroutine is invoked with <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">vl</span></span></span> in conjunction with <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">globalcheck=.false.</span></span></span>,
|
|
no index space scan will take place. Thus it is the responsibility of the user to
|
|
make sure that the indices specified in <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">vl</span></span></span> have neither orphans nor overlaps; if
|
|
this assumption fails, results will be unpredictable.
|
|
</li>
|
|
<li
|
|
class="enumerate" id="x41-78014x7">Orphan and overlap indices are impossible by construction when the subroutine
|
|
is invoked with <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">nl</span></span></span> (alone), or <span class="obeylines-h"><span class="verb"><span
|
|
class="cmtt-10">vg</span></span></span>.</li></ol>
|
|
|
|
|
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