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<head><title>init &#8212; Initialize a preconditioner</title>
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<h4 class="subsectionHead"><span class="titlemark">10.1 </span> <a
id="x99-13600010.1"></a>init &#8212; Initialize a preconditioner</h4>
<pre class="verbatim" id="verbatim-97">
call&#x00A0;prec%init(icontxt,ptype,&#x00A0;info)
</pre>
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<dl class="description"><dt class="description">
<span
class="cmbx-10">Type:</span> </dt><dd
class="description">Asynchronous.
</dd><dt class="description">
<span
class="cmbx-10">On Entry</span> </dt><dd
class="description">
</dd><dt class="description">
<span
class="cmbx-10">icontxt</span> </dt><dd
class="description">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">
<span
class="cmbx-10">ptype</span> </dt><dd
class="description">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">
<span
class="cmbx-10">On Exit</span> </dt><dd
class="description">
</dd><dt class="description">
<span
class="cmbx-10">prec</span> </dt><dd
class="description">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="userhtmlsu8.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">
<span
class="cmbx-10">info</span> </dt><dd
class="description">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="userhtml100.html#fn4x0"><sup class="textsuperscript">4</sup></a></span><a
id="x99-136001f4"></a> :
<dl class="description"><dt class="description">
<span
class="cmbx-10">NONE</span> </dt><dd
class="description">No preconditioning, i.e. the preconditioner is just a copy operator.
</dd><dt class="description">
<span
class="cmbx-10">DIAG</span> </dt><dd
class="description">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">
<span
class="cmbx-10">BJAC</span> </dt><dd
class="description">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>
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