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62 lines
3.3 KiB
HTML
62 lines
3.3 KiB
HTML
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<head><title>Programming model</title>
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<h4 class="subsectionHead"><span class="titlemark">2.4 </span> <a
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id="x11-80002.4"></a>Programming model</h4>
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<!--l. 450--><p class="noindent" >The PSBLAS librarary is based on the Single Program Multiple Data (SPMD)
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programming model: each process participating in the computation performs the
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same actions on a chunk of data. Parallelism is thus data-driven.
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<!--l. 455--><p class="indent" > Because of this structure, many subroutines coordinate their action across the
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various processes, thus providing an implicit synchronization point, and therefore
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<span
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class="cmti-10">must </span>be called simultaneously by all processes participating in the computation. This
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is certainly true for the data allocation and assembly routines, for all the
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computational routines and for some of the tools routines.
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<!--l. 463--><p class="indent" > However there are many cases where no synchronization, and indeed no
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communication among processes, is implied; for instance, all the routines in sec. <a
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href="userhtmlse3.html#x12-90003">3<!--tex4ht:ref: sec:datastruct --></a>
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are only acting on the local data structures, and thus may be called independently.
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The most important case is that of the coefficient insertion routines: since the
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number of coefficients in the sparse and dense matrices varies among the processors,
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and since the user is free to choose an arbitrary order in builiding the matrix entries,
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these routines cannot imply a synchronization.
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<!--l. 473--><p class="indent" > Throughout this user’s guide each subroutine will be clearly indicated
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as:
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<dl class="description"><dt class="description">
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<span
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class="cmbx-10">Synchronous:</span> </dt><dd
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class="description">must be called simultaneously by all the processes in the
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relevant communication context;
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</dd><dt class="description">
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<span
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class="cmbx-10">Asynchronous:</span> </dt><dd
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class="description">may be called in a totally independent manner.</dd></dl>
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