<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html > <head><title>Preconditioner routines</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="generator" content="TeX4ht (https://tug.org/tex4ht/)"> <meta name="originator" content="TeX4ht (https://tug.org/tex4ht/)"> <!-- html,3 --> <meta name="src" content="userhtml.tex"> <link rel="stylesheet" type="text/css" href="userhtml.css"> </head><body > <!--l. 1--><div class="crosslinks"><p class="noindent">[<a href="userhtmlse9.html" >prev</a>] [<a href="userhtmlse9.html#tailuserhtmlse9.html" >prev-tail</a>] [<a href="userhtmlse7.html#tailuserhtmlse10.html">tail</a>] [<a href="userhtml.html#userhtmlse13.html" >up</a>] </p></div> <h3 class="sectionHead"><span class="titlemark">10 </span> <a id="x15-13500010"></a>Preconditioner routines</h3> <!--l. 6--><p class="noindent" >The base PSBLAS library contains the implementation of two simple preconditioning techniques: <ul class="itemize1"> <li class="itemize"> <!--l. 9--><p class="noindent" >Diagonal Scaling </li> <li class="itemize"> <!--l. 10--><p class="noindent" >Block Jacobi with ILU(0) factorization</li></ul> <!--l. 14--><p class="noindent" >The supporting data type and subroutine interfaces are defined in the module <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_prec_mod</span></span></span>. The old interfaces <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_precinit</span></span></span> and <span class="obeylines-h"><span class="verb"><span class="cmtt-10">psb_precbld</span></span></span> are still supported for backward compatibility <h4 class="subsectionHead"><span class="titlemark">10.1 </span> <a id="x15-13600010.1"></a>init — Initialize a preconditioner</h4> <pre class="verbatim" id="verbatim-97"> call prec%init(icontxt,ptype, info) </pre> <!--l. 30--><p class="nopar" > <!--l. 32--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 33--><p class="noindent" > <span class="cmbx-10">Type:</span> </dt><dd class="description"> <!--l. 33--><p class="noindent" >Asynchronous. </dd><dt class="description"> <!--l. 34--><p class="noindent" > <span class="cmbx-10">On Entry</span> </dt><dd class="description"> <!--l. 34--><p class="noindent" > </dd><dt class="description"> <!--l. 35--><p class="noindent" > <span class="cmbx-10">icontxt</span> </dt><dd class="description"> <!--l. 35--><p class="noindent" >the communication context.<br class="newline" />Scope:<span class="cmbx-10">global</span>.<br class="newline" />Type:<span class="cmbx-10">required</span>.<br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: an integer value. </dd><dt class="description"> <!--l. 40--><p class="noindent" > <span class="cmbx-10">ptype</span> </dt><dd class="description"> <!--l. 40--><p class="noindent" >the type of preconditioner. Scope: <span class="cmbx-10">global </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: a character string, see usage notes. </dd><dt class="description"> <!--l. 53--><p class="noindent" > <span class="cmbx-10">On Exit</span> </dt><dd class="description"> <!--l. 53--><p class="noindent" > </dd><dt class="description"> <!--l. 55--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 55--><p class="noindent" >Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: a preconditioner data structure <a href="userhtmlse3.html#precdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_prec</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 60--><p class="noindent" > <span class="cmbx-10">info</span> </dt><dd class="description"> <!--l. 60--><p class="noindent" >Scope: <span class="cmbx-10">global </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">out</span>.<br class="newline" />Error code: if no error, 0 is returned.</dd></dl> <!--l. 66--><p class="noindent" ><span class="cmbx-12">Notes </span>Legal inputs to this subroutine are interpreted depending on the <span class="cmmi-10">ptype </span>string as follows<span class="footnote-mark"><a href="userhtml16.html#fn4x0"><sup class="textsuperscript">4</sup></a></span><a id="x15-136001f4"></a> : <dl class="description"><dt class="description"> <!--l. 74--><p class="noindent" > <span class="cmbx-10">NONE</span> </dt><dd class="description"> <!--l. 74--><p class="noindent" >No preconditioning, i.e. the preconditioner is just a copy operator. </dd><dt class="description"> <!--l. 76--><p class="noindent" > <span class="cmbx-10">DIAG</span> </dt><dd class="description"> <!--l. 76--><p class="noindent" >Diagonal scaling; each entry of the input vector is multiplied by the reciprocal of the sum of the absolute values of the coefficients in the corresponding row of matrix <span class="cmmi-10">A</span>; </dd><dt class="description"> <!--l. 79--><p class="noindent" > <span class="cmbx-10">BJAC</span> </dt><dd class="description"> <!--l. 79--><p class="noindent" >Precondition by a factorization of the block-diagonal of matrix <span class="cmmi-10">A</span>, where block boundaries are determined by the data allocation boundaries for each process; requires no communication. Only the incomplete factorization <span class="cmmi-10">ILU</span>(0) is currently implemented.</dd></dl> <h4 class="subsectionHead"><span class="titlemark">10.2 </span> <a id="x15-13700010.2"></a>build — Builds a preconditioner</h4> <pre class="verbatim" id="verbatim-98"> call prec%build(a, desc_a, info[,amold,vmold,imold]) </pre> <!--l. 91--><p class="nopar" > <!--l. 93--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 94--><p class="noindent" > <span class="cmbx-10">Type:</span> </dt><dd class="description"> <!--l. 94--><p class="noindent" >Synchronous. </dd><dt class="description"> <!--l. 95--><p class="noindent" > <span class="cmbx-10">On Entry</span> </dt><dd class="description"> <!--l. 95--><p class="noindent" > </dd><dt class="description"> <!--l. 96--><p class="noindent" > <span class="cmbx-10">a</span> </dt><dd class="description"> <!--l. 96--><p class="noindent" >the system sparse matrix. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">in</span>, target.<br class="newline" />Specified as: a sparse matrix data structure <a href="userhtmlse3.html#spdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_Tspmat</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 101--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 101--><p class="noindent" >the preconditioner.<br class="newline" />Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: an already initialized precondtioner data structure <a href="userhtmlse3.html#precdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_prec</span><span class="cmtt-10">_type</span></a><br class="newline" /> </dd><dt class="description"> <!--l. 106--><p class="noindent" > <span class="cmbx-10">desc</span><span class="cmbx-10">_a</span> </dt><dd class="description"> <!--l. 106--><p class="noindent" >the problem communication descriptor. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">in</span>, target.<br class="newline" />Specified as: a communication descriptor data structure <a href="userhtmlse3.html#descdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_desc</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 116--><p class="noindent" > <span class="cmbx-10">amold</span> </dt><dd class="description"> <!--l. 116--><p class="noindent" >The desired dynamic type for the internal matrix storage.<br class="newline" />Scope: <span class="cmbx-10">local</span>.<br class="newline" />Type: <span class="cmbx-10">optional</span>.<br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: an object of a class derived from <a id="spbasedata"></a><span class="cmtt-10">psb</span><span class="cmtt-10">_T</span><span class="cmtt-10">_base</span><span class="cmtt-10">_sparse</span><span class="cmtt-10">_mat</span>. </dd><dt class="description"> <!--l. 121--><p class="noindent" > <span class="cmbx-10">vmold</span> </dt><dd class="description"> <!--l. 121--><p class="noindent" >The desired dynamic type for the internal vector storage.<br class="newline" />Scope: <span class="cmbx-10">local</span>.<br class="newline" />Type: <span class="cmbx-10">optional</span>.<br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: an object of a class derived from <a id="vbasedata"></a><span class="cmtt-10">psb</span><span class="cmtt-10">_T</span><span class="cmtt-10">_base</span><span class="cmtt-10">_vect</span><span class="cmtt-10">_type</span>. </dd><dt class="description"> <!--l. 126--><p class="noindent" > <span class="cmbx-10">imold</span> </dt><dd class="description"> <!--l. 126--><p class="noindent" >The desired dynamic type for the internal integer vector storage.<br class="newline" />Scope: <span class="cmbx-10">local</span>.<br class="newline" />Type: <span class="cmbx-10">optional</span>.<br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: an object of a class derived from (integer) <a id="vbasedata"></a><span class="cmtt-10">psb</span><span class="cmtt-10">_T</span><span class="cmtt-10">_base</span><span class="cmtt-10">_vect</span><span class="cmtt-10">_type</span>.</dd></dl> <!--l. 133--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 134--><p class="noindent" > <span class="cmbx-10">On Return</span> </dt><dd class="description"> <!--l. 134--><p class="noindent" > </dd><dt class="description"> <!--l. 135--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 135--><p class="noindent" >the preconditioner.<br class="newline" />Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: a precondtioner data structure <a href="userhtmlse3.html#precdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_prec</span><span class="cmtt-10">_type</span></a><br class="newline" /> </dd><dt class="description"> <!--l. 140--><p class="noindent" > <span class="cmbx-10">info</span> </dt><dd class="description"> <!--l. 140--><p class="noindent" >Error code.<br class="newline" />Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required </span><br class="newline" />Intent: <span class="cmbx-10">out</span>.<br class="newline" />An integer value; 0 means no error has been detected.</dd></dl> <!--l. 146--><p class="noindent" >The <span class="obeylines-h"><span class="verb"><span class="cmtt-10">amold</span></span></span>, <span class="obeylines-h"><span class="verb"><span class="cmtt-10">vmold</span></span></span> and <span class="obeylines-h"><span class="verb"><span class="cmtt-10">imold</span></span></span> arguments may be employed to interface with special devices, such as GPUs and other accelerators. <h4 class="subsectionHead"><span class="titlemark">10.3 </span> <a id="x15-13800010.3"></a>apply — Preconditioner application routine</h4> <pre class="verbatim" id="verbatim-99"> call prec%apply(x,y,desc_a,info,trans,work) call prec%apply(x,desc_a,info,trans) </pre> <!--l. 158--><p class="nopar" > <!--l. 160--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 161--><p class="noindent" > <span class="cmbx-10">Type:</span> </dt><dd class="description"> <!--l. 161--><p class="noindent" >Synchronous. </dd><dt class="description"> <!--l. 162--><p class="noindent" > <span class="cmbx-10">On Entry</span> </dt><dd class="description"> <!--l. 162--><p class="noindent" > </dd><dt class="description"> <!--l. 163--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 163--><p class="noindent" >the preconditioner. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: a preconditioner data structure <a href="userhtmlse3.html#precdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_prec</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 168--><p class="noindent" > <span class="cmbx-10">x</span> </dt><dd class="description"> <!--l. 168--><p class="noindent" >the source vector. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: a rank one array or an object of type <a href="userhtmlse3.html#vdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_T</span><span class="cmtt-10">_vect</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 173--><p class="noindent" > <span class="cmbx-10">desc</span><span class="cmbx-10">_a</span> </dt><dd class="description"> <!--l. 173--><p class="noindent" >the problem communication descriptor. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: a communication data structure <a href="userhtmlse3.html#descdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_desc</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 178--><p class="noindent" > <span class="cmbx-10">trans</span> </dt><dd class="description"> <!--l. 178--><p class="noindent" >Scope: <br class="newline" />Type: <span class="cmbx-10">optional</span><br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: a character. </dd><dt class="description"> <!--l. 183--><p class="noindent" > <span class="cmbx-10">work</span> </dt><dd class="description"> <!--l. 183--><p class="noindent" >an optional work space Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">optional</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: a double precision array.</dd></dl> <!--l. 190--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 191--><p class="noindent" > <span class="cmbx-10">On Return</span> </dt><dd class="description"> <!--l. 191--><p class="noindent" > </dd><dt class="description"> <!--l. 192--><p class="noindent" > <span class="cmbx-10">y</span> </dt><dd class="description"> <!--l. 192--><p class="noindent" >the destination vector. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: a rank one array or an object of type <a href="userhtmlse3.html#vdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_T</span><span class="cmtt-10">_vect</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 197--><p class="noindent" > <span class="cmbx-10">info</span> </dt><dd class="description"> <!--l. 197--><p class="noindent" >Error code.<br class="newline" />Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required </span><br class="newline" />Intent: <span class="cmbx-10">out</span>.<br class="newline" />An integer value; 0 means no error has been detected.</dd></dl> <h4 class="subsectionHead"><span class="titlemark">10.4 </span> <a id="x15-13900010.4"></a>descr — Prints a description of current preconditioner</h4> <pre class="verbatim" id="verbatim-100"> call prec%descr(info) call prec%descr(info,iout, root) </pre> <!--l. 212--><p class="nopar" > <!--l. 214--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 215--><p class="noindent" > <span class="cmbx-10">Type:</span> </dt><dd class="description"> <!--l. 215--><p class="noindent" >Asynchronous. </dd><dt class="description"> <!--l. 216--><p class="noindent" > <span class="cmbx-10">On Entry</span> </dt><dd class="description"> <!--l. 216--><p class="noindent" > </dd><dt class="description"> <!--l. 217--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 217--><p class="noindent" >the preconditioner. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: a preconditioner data structure <a href="userhtmlse3.html#precdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_prec</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 222--><p class="noindent" > <span class="cmbx-10">iout</span> </dt><dd class="description"> <!--l. 222--><p class="noindent" >output unit. Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">optional</span><br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: an integer number. Default: default output unit. </dd><dt class="description"> <!--l. 227--><p class="noindent" > <span class="cmbx-10">root</span> </dt><dd class="description"> <!--l. 227--><p class="noindent" >Process from which to print Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">optional</span><br class="newline" />Intent: <span class="cmbx-10">in</span>.<br class="newline" />Specified as: an integer number between 0 and <span class="cmmi-10">np </span><span class="cmsy-10">- </span>1, in which case the specified process will print the description, or <span class="cmsy-10">-</span>1, in which case all processes will print. Default: 0. </dd><dt class="description"> <!--l. 234--><p class="noindent" > <span class="cmbx-10">On Return</span> </dt><dd class="description"> <!--l. 234--><p class="noindent" > </dd><dt class="description"> <!--l. 235--><p class="noindent" > <span class="cmbx-10">info</span> </dt><dd class="description"> <!--l. 235--><p class="noindent" >Error code.<br class="newline" />Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required </span><br class="newline" />Intent: <span class="cmbx-10">out</span>.<br class="newline" />An integer value; 0 means no error has been detected.</dd></dl> <h4 class="subsectionHead"><span class="titlemark">10.5 </span> <a id="x15-14000010.5"></a>clone — clone current preconditioner</h4> <pre class="verbatim" id="verbatim-101"> call  prec%clone(precout,info) </pre> <!--l. 248--><p class="nopar" > <!--l. 250--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 251--><p class="noindent" > <span class="cmbx-10">Type:</span> </dt><dd class="description"> <!--l. 251--><p class="noindent" >Asynchronous. </dd><dt class="description"> <!--l. 252--><p class="noindent" > <span class="cmbx-10">On Entry</span> </dt><dd class="description"> <!--l. 252--><p class="noindent" > </dd><dt class="description"> <!--l. 253--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 253--><p class="noindent" >the preconditioner.<br class="newline" />Scope: <span class="cmbx-10">local</span>.<br class="newline" /></dd></dl> <!--l. 260--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 261--><p class="noindent" > <span class="cmbx-10">On Return</span> </dt><dd class="description"> <!--l. 261--><p class="noindent" > </dd><dt class="description"> <!--l. 262--><p class="noindent" > <span class="cmbx-10">precout</span> </dt><dd class="description"> <!--l. 262--><p class="noindent" >A copy of the input object. </dd><dt class="description"> <!--l. 263--><p class="noindent" > <span class="cmbx-10">info</span> </dt><dd class="description"> <!--l. 263--><p class="noindent" >Return code.</dd></dl> <h4 class="subsectionHead"><span class="titlemark">10.6 </span> <a id="x15-14100010.6"></a>free — Free a preconditioner</h4> <pre class="verbatim" id="verbatim-102"> call prec%free(info) </pre> <!--l. 271--><p class="nopar" > <!--l. 273--><p class="indent" > <dl class="description"><dt class="description"> <!--l. 274--><p class="noindent" > <span class="cmbx-10">Type:</span> </dt><dd class="description"> <!--l. 274--><p class="noindent" >Asynchronous. </dd><dt class="description"> <!--l. 275--><p class="noindent" > <span class="cmbx-10">On Entry</span> </dt><dd class="description"> <!--l. 275--><p class="noindent" > </dd><dt class="description"> <!--l. 276--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 276--><p class="noindent" >the preconditioner.<br class="newline" />Scope: <span class="cmbx-10">local</span>.<br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: a preconditioner data structure <a href="userhtmlse3.html#precdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_prec</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 289--><p class="noindent" > <span class="cmbx-10">On Exit</span> </dt><dd class="description"> <!--l. 289--><p class="noindent" > </dd><dt class="description"> <!--l. 291--><p class="noindent" > <span class="cmbx-10">prec</span> </dt><dd class="description"> <!--l. 291--><p class="noindent" >Scope: <span class="cmbx-10">local </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">inout</span>.<br class="newline" />Specified as: a preconditioner data structure <a href="userhtmlse3.html#precdata"><span class="cmtt-10">psb</span><span class="cmtt-10">_prec</span><span class="cmtt-10">_type</span></a>. </dd><dt class="description"> <!--l. 296--><p class="noindent" > <span class="cmbx-10">info</span> </dt><dd class="description"> <!--l. 296--><p class="noindent" >Scope: <span class="cmbx-10">global </span><br class="newline" />Type: <span class="cmbx-10">required</span><br class="newline" />Intent: <span class="cmbx-10">out</span>.<br class="newline" />Error code: if no error, 0 is returned.</dd></dl> <!--l. 302--><p class="noindent" ><span class="cmbx-12">Notes </span>Releases all internal storage. <!--l. 1--><div class="crosslinks"><p class="noindent">[<a href="userhtmlse9.html" >prev</a>] [<a href="userhtmlse9.html#tailuserhtmlse9.html" >prev-tail</a>] [<a href="userhtmlse10.html" >front</a>] [<a href="userhtml.html#userhtmlse13.html" >up</a>] </p></div> <!--l. 1--><p class="indent" > <a id="tailuserhtmlse10.html"></a> </body></html>