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Docs and krylov->linsolve changes
This commit is contained in:
Salvatore Filippone
+68
-59
@@ -432,18 +432,18 @@ matrix/vector creation and linear system solution as follows:
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<li
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class="enumerate" id="x4-6002x1">
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<!--l. 347--><p class="noindent" >Initialize parallel environment with <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">psb_init</span></span></span>
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||||
class="cmtt-10">psb_init</span></span></span>;
|
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</li>
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<li
|
||||
class="enumerate" id="x4-6004x2">
|
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<!--l. 348--><p class="noindent" >Initialize index space with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_cdall</span></span></span>
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class="cmtt-10">psb_cdall</span></span></span>;
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</li>
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<li
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class="enumerate" id="x4-6006x3">
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<!--l. 349--><p class="noindent" >Allocate sparse matrix and dense vectors with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_spall</span></span></span> and <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_geall</span></span></span>
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class="cmtt-10">psb_geall</span></span></span>;
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</li>
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<li
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class="enumerate" id="x4-6008x4">
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@@ -459,12 +459,12 @@ class="cmtt-10">psb_geins</span></span></span>
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<li
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class="enumerate" id="x4-6012x1">
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<!--l. 355--><p class="noindent" ><span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_cdasb</span></span></span>
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class="cmtt-10">psb_cdasb</span></span></span>,
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</li>
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<li
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class="enumerate" id="x4-6014x2">
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<!--l. 356--><p class="noindent" ><span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_spasb</span></span></span>
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class="cmtt-10">psb_spasb</span></span></span>,
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@@ -472,106 +472,118 @@ class="cmtt-10">psb_spasb</span></span></span>
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<li
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class="enumerate" id="x4-6016x3">
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<!--l. 357--><p class="noindent" ><span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_geasb</span></span></span></li></ol>
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class="cmtt-10">psb_geasb</span></span></span>;</li></ol>
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</li>
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<li
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class="enumerate" id="x4-6018x6">
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<!--l. 359--><p class="noindent" >Choose the preconditioner to be used with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">prec%init</span></span></span> and build it with
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class="cmtt-10">prec%init</span></span></span> and <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">prec%set</span></span></span>, and build it with
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<span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">prec%build</span></span></span><span class="footnote-mark"><a
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href="userhtml7.html#fn3x0"><sup class="textsuperscript">3</sup></a></span><a
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id="x4-6019f3"></a> .
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id="x4-6019f3"></a> ;
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</li>
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<li
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class="enumerate" id="x4-6022x7">
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<!--l. 363--><p class="noindent" >Call the iterative driver <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_krylov</span></span></span> with the method of choice, e.g.
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<span class="obeylines-h"><span class="verb"><span
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<!--l. 364--><p class="noindent" >Call one of the iterative drivers with the method of choice, e.g. <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_krylov</span></span></span>
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with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">bicgstab</span></span></span>.</li></ol>
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<!--l. 366--><p class="noindent" >This is the structure of the sample programs in the directory <span class="obeylines-h"><span class="verb"><span
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<!--l. 367--><p class="noindent" >This is the structure of the sample programs in the directory <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">test/pargen/</span></span></span>.
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<!--l. 369--><p class="indent" > For a simulation in which the same discretization mesh is used over multiple time
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<!--l. 370--><p class="indent" > For a simulation in which the same discretization mesh is used over multiple time
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steps, the following structure may be more appropriate:
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<ol class="enumerate1" >
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<li
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class="enumerate" id="x4-6024x1">
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<!--l. 372--><p class="noindent" >Initialize parallel environment with <span class="obeylines-h"><span class="verb"><span
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<!--l. 373--><p class="noindent" >Initialize parallel environment with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_init</span></span></span>
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</li>
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<li
|
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class="enumerate" id="x4-6026x2">
|
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<!--l. 373--><p class="noindent" >Initialize index space with <span class="obeylines-h"><span class="verb"><span
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<!--l. 374--><p class="noindent" >Initialize index space with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_cdall</span></span></span>
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</li>
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<li
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class="enumerate" id="x4-6028x3">
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<!--l. 374--><p class="noindent" >Loop over the topology of the discretization mesh and build the descriptor
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<!--l. 375--><p class="noindent" >Loop over the topology of the discretization mesh and build the descriptor
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with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_cdins</span></span></span>
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class="cmtt-10">psb_cdins</span></span></span>;
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</li>
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<li
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class="enumerate" id="x4-6030x4">
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<!--l. 376--><p class="noindent" >Assemble the descriptor with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_cdasb</span></span></span>
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<!--l. 377--><p class="noindent" >Assemble the descriptor with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_cdasb</span></span></span>;
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</li>
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<li
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class="enumerate" id="x4-6032x5">
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<!--l. 377--><p class="noindent" >Allocate the sparse matrices and dense vectors with <span class="obeylines-h"><span class="verb"><span
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<!--l. 378--><p class="noindent" >Allocate the sparse matrices and dense vectors with; <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_spall</span></span></span> and
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<span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_geall</span></span></span>
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class="cmtt-10">psb_geall</span></span></span>;
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</li>
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<li
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class="enumerate" id="x4-6034x6">
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<!--l. 379--><p class="noindent" >Loop over the time steps:
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<!--l. 380--><p class="noindent" >Loop over the time steps:
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<ol class="enumerate2" >
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<li
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class="enumerate" id="x4-6036x1">
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<!--l. 381--><p class="noindent" >If after first time step, reinitialize the sparse matrix with <span class="obeylines-h"><span class="verb"><span
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<!--l. 382--><p class="noindent" >If after first time step, reinitialize the sparse matrix with <span class="obeylines-h"><span class="verb"><span
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class="cmtt-10">psb_sprn</span></span></span>;
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also zero out the dense vectors;
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||||
</li>
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<li
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||||
class="enumerate" id="x4-6038x2">
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<!--l. 384--><p class="noindent" >Loop over the mesh, generate the coefficients and insert/update them
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<!--l. 385--><p class="noindent" >Loop over the mesh, generate the coefficients and insert/update them
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with <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">psb_spins</span></span></span> and <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">psb_geins</span></span></span>
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||||
class="cmtt-10">psb_geins</span></span></span>;
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||||
</li>
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||||
<li
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||||
class="enumerate" id="x4-6040x3">
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<!--l. 386--><p class="noindent" >Assemble with <span class="obeylines-h"><span class="verb"><span
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||||
<!--l. 387--><p class="noindent" >Assemble with <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">psb_spasb</span></span></span> and <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">psb_geasb</span></span></span>
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||||
class="cmtt-10">psb_geasb</span></span></span>;
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||||
</li>
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<li
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||||
class="enumerate" id="x4-6042x4">
|
||||
<!--l. 387--><p class="noindent" >Choose and build preconditioner with <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">prec%init</span></span></span> and <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">prec%build</span></span></span>
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||||
<!--l. 388--><p class="noindent" >
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||||
</li>
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||||
<li
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||||
class="enumerate" id="x4-6044x5">
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||||
<!--l. 389--><p class="noindent" >Call the iterative method of choice, e.g. <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">psb_bicgstab</span></span></span></li></ol>
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||||
<!--l. 388--><p class="noindent" >Choose the preconditioner to be used with <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">prec%init</span></span></span> and <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">prec%set</span></span></span>,
|
||||
and build it with <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">prec%build</span></span></span>;
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||||
</li>
|
||||
<li
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||||
class="enumerate" id="x4-6046x6">
|
||||
<!--l. 391--><p class="noindent" >Call one of the iterative drivers with the method of choice, e.g.
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||||
<span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">psb_krylov</span></span></span> with <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">bicgstab</span></span></span>.</li></ol>
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||||
</li></ol>
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<!--l. 392--><p class="noindent" >The insertion routines will be called as many times as needed; they only need to be
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<!--l. 395--><p class="noindent" >The insertion routines will be called as many times as needed; they only need to be
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called on the data that is actually allocated to the current process, i.e. each process
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generates its own data.
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<!--l. 397--><p class="indent" > In principle there is no specific order in the calls to <span class="obeylines-h"><span class="verb"><span
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<!--l. 400--><p class="indent" > In principle there is no specific order in the calls to <span class="obeylines-h"><span class="verb"><span
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||||
class="cmtt-10">psb_spins</span></span></span>, nor is there a
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requirement to build a matrix row in its entirety before calling the routine; this
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allows the application programmer to walk through the discretization mesh element
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by element, generating the main part of a given matrix row but also contributions to
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the rows corresponding to neighbouring elements.
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<!--l. 404--><p class="indent" > From a functional point of view it is even possible to execute one call for each
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<!--l. 407--><p class="indent" > From a functional point of view it is even possible to execute one call for each
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nonzero coefficient; however this would have a substantial computational
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overhead. It is therefore advisable to pack a certain amount of data into each
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call to the insertion routine, say touching on a few tens of rows; the best
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||||
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||||
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||||
performng value would depend on both the architecture of the computer being
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used and on the problem structure. At the opposite extreme, it would be
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possible to generate the entire part of a coefficient matrix residing on a
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@@ -579,40 +591,37 @@ process and pass it in a single call to <span class="obeylines-h"><span class="v
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class="cmtt-10">psb_spins</span></span></span>; this, however, would entail a
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doubling of memory occupation, and thus would be almost always far from
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optimal.
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<!--l. 417--><p class="noindent" >
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||||
<!--l. 420--><p class="noindent" >
|
||||
<h5 class="subsubsectionHead"><span class="titlemark">2.3.1 </span> <a
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||||
id="x4-70002.3.1"></a>User-defined index mappings</h5>
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<!--l. 419--><p class="noindent" >PSBLAS supports user-defined global to local index mappings, subject to the
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<!--l. 422--><p class="noindent" >PSBLAS supports user-defined global to local index mappings, subject to the
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constraints outlined in sec. <a
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||||
href="#x4-60002.3">2.3<!--tex4ht:ref: sec:appstruct --></a>:
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||||
<ol class="enumerate1" >
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||||
<li
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||||
class="enumerate" id="x4-7002x1">
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||||
<!--l. 422--><p class="noindent" >The set of indices owned locally must be mapped to the set 1<span
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<!--l. 425--><p class="noindent" >The set of indices owned locally must be mapped to the set 1<span
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class="cmmi-10">…</span><span
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class="cmmi-10">n</span><sub>row<sub><span
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||||
class="cmmi-5">i</span></sub></sub>;
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||||
</li>
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||||
<li
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||||
class="enumerate" id="x4-7004x2">
|
||||
<!--l. 424--><p class="noindent" >The set of halo points must be mapped to the set <span
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||||
<!--l. 427--><p class="noindent" >The set of halo points must be mapped to the set <span
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||||
class="cmmi-10">n</span><sub>row<sub><span
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||||
class="cmmi-5">i</span></sub></sub> + 1<span
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||||
class="cmmi-10">…</span><span
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||||
class="cmmi-10">n</span><sub>col<sub>
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||||
<span
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||||
class="cmmi-5">i</span></sub></sub>;</li></ol>
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<!--l. 427--><p class="noindent" >but otherwise the mapping is arbitrary. The user application is responsible to ensure
|
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<!--l. 430--><p class="noindent" >but otherwise the mapping is arbitrary. The user application is responsible to ensure
|
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consistency of this mapping; some errors may be caught by the library, but
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this is not guaranteed. The application structure to support this usage is as
|
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follows:
|
||||
<ol class="enumerate1" >
|
||||
<li
|
||||
class="enumerate" id="x4-7006x1">
|
||||
<!--l. 433--><p class="noindent" >Initialize index
|
||||
<!--l. 436--><p class="noindent" >Initialize index
|
||||
space with <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">psb_cdall(ictx,desc,info,vl=vl,lidx=lidx)</span></span></span> passing the
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vectors <span class="obeylines-h"><span class="verb"><span
|
||||
@@ -622,7 +631,7 @@ class="cmtt-10">lidx(:)</span></span></span> containing the corresponding local
|
||||
</li>
|
||||
<li
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||||
class="enumerate" id="x4-7008x2">
|
||||
<!--l. 438--><p class="noindent" >Add the halo points <span class="obeylines-h"><span class="verb"><span
|
||||
<!--l. 441--><p class="noindent" >Add the halo points <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">ja(:)</span></span></span> and their associated local indices <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">lidx(:)</span></span></span> with
|
||||
a(some) call(s) to <span class="obeylines-h"><span class="verb"><span
|
||||
@@ -630,12 +639,15 @@ class="cmtt-10">psb_cdins(nz,ja,desc,info,lidx=lidx)</span></span></span>;
|
||||
</li>
|
||||
<li
|
||||
class="enumerate" id="x4-7010x3">
|
||||
<!--l. 441--><p class="noindent" >Assemble the descriptor with <span class="obeylines-h"><span class="verb"><span
|
||||
<!--l. 444--><p class="noindent" >Assemble the descriptor with <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">psb_cdasb</span></span></span>;
|
||||
</li>
|
||||
<li
|
||||
class="enumerate" id="x4-7012x4">
|
||||
<!--l. 442--><p class="noindent" >Build the sparse matrices and vectors, optionally making use in <span class="obeylines-h"><span class="verb"><span
|
||||
|
||||
|
||||
|
||||
<!--l. 445--><p class="noindent" >Build the sparse matrices and vectors, optionally making use in <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">psb_spins</span></span></span>
|
||||
and <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">psb_geins</span></span></span> of the <span class="obeylines-h"><span class="verb"><span
|
||||
@@ -644,22 +656,19 @@ class="cmtt-10">ia</span></span></span>,
|
||||
<span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">ja</span></span></span> and <span class="obeylines-h"><span class="verb"><span
|
||||
class="cmtt-10">irw</span></span></span>, respectively, are already local indices.</li></ol>
|
||||
|
||||
|
||||
|
||||
<!--l. 449--><p class="noindent" >
|
||||
<!--l. 452--><p class="noindent" >
|
||||
<h4 class="subsectionHead"><span class="titlemark">2.4 </span> <a
|
||||
id="x4-80002.4"></a>Programming model</h4>
|
||||
<!--l. 451--><p class="noindent" >The PSBLAS librarary is based on the Single Program Multiple Data (SPMD)
|
||||
<!--l. 454--><p class="noindent" >The PSBLAS librarary is based on the Single Program Multiple Data (SPMD)
|
||||
programming model: each process participating in the computation performs the
|
||||
same actions on a chunk of data. Parallelism is thus data-driven.
|
||||
<!--l. 456--><p class="indent" > Because of this structure, many subroutines coordinate their action across the
|
||||
<!--l. 459--><p class="indent" > Because of this structure, many subroutines coordinate their action across the
|
||||
various processes, thus providing an implicit synchronization point, and therefore
|
||||
<span
|
||||
class="cmti-10">must </span>be called simultaneously by all processes participating in the computation. This
|
||||
is certainly true for the data allocation and assembly routines, for all the
|
||||
computational routines and for some of the tools routines.
|
||||
<!--l. 464--><p class="indent" > However there are many cases where no synchronization, and indeed no
|
||||
<!--l. 467--><p class="indent" > However there are many cases where no synchronization, and indeed no
|
||||
communication among processes, is implied; for instance, all the routines in sec. <a
|
||||
href="userhtmlse3.html#x8-90003">3<!--tex4ht:ref: sec:datastruct --></a>
|
||||
are only acting on the local data structures, and thus may be called independently.
|
||||
@@ -667,21 +676,21 @@ The most important case is that of the coefficient insertion routines: since the
|
||||
number of coefficients in the sparse and dense matrices varies among the processors,
|
||||
and since the user is free to choose an arbitrary order in builiding the matrix entries,
|
||||
these routines cannot imply a synchronization.
|
||||
<!--l. 474--><p class="indent" > Throughout this user’s guide each subroutine will be clearly indicated
|
||||
<!--l. 477--><p class="indent" > Throughout this user’s guide each subroutine will be clearly indicated
|
||||
as:
|
||||
<dl class="description"><dt class="description">
|
||||
<!--l. 477--><p class="noindent" >
|
||||
<!--l. 480--><p class="noindent" >
|
||||
<span
|
||||
class="cmbx-10">Synchronous:</span> </dt><dd
|
||||
class="description">
|
||||
<!--l. 477--><p class="noindent" >must be called simultaneously by all the processes in the relevant
|
||||
<!--l. 480--><p class="noindent" >must be called simultaneously by all the processes in the relevant
|
||||
communication context;
|
||||
</dd><dt class="description">
|
||||
<!--l. 479--><p class="noindent" >
|
||||
<!--l. 482--><p class="noindent" >
|
||||
<span
|
||||
class="cmbx-10">Asynchronous:</span> </dt><dd
|
||||
class="description">
|
||||
<!--l. 479--><p class="noindent" >may be called in a totally independent manner.</dd></dl>
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<!--l. 482--><p class="noindent" >may be called in a totally independent manner.</dd></dl>
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Reference in New Issue
Block a user