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   <h4 class="subsectionHead"><span class="titlemark">7.14   </span> <a 
 id="x82-1190007.14"></a>psb_amn &#8212; Global minimum absolute value</h4>
                                                                  

                                                                  
   <pre class="verbatim" id="verbatim-84">
call&#x00A0;psb_amn(ctxt,&#x00A0;dat&#x00A0;[,&#x00A0;root,&#x00A0;mode,&#x00A0;request])
</pre>
<!--l. 851--><p class="nopar" >
<!--l. 853--><p class="indent" >   This subroutine implements a minimum absolute value reduction operation based
on the underlying communication library.
     <dl class="description"><dt class="description">
<span 
class="cmbx-10">Type:</span> </dt><dd 
class="description">Synchronous.
     </dd><dt class="description">
<span 
class="cmbx-10">On Entry</span>  </dt><dd 
class="description">
     </dd><dt class="description">
<span 
class="cmbx-10">ctxt</span> </dt><dd 
class="description">the communication context identifying the virtual parallel machine.<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 variable.
     </dd><dt class="description">
<span 
class="cmbx-10">dat</span> </dt><dd 
class="description">The local contribution to the global minimum.<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 integer, real or complex variable, which may be a scalar, or
     a rank 1 or 2 array. &#x00A0;Type, kind, rank and size must agree on all processes.
     </dd><dt class="description">
<span 
class="cmbx-10">root</span> </dt><dd 
class="description">Process to hold the final value, or <span 
class="cmsy-10">-</span>1 to make it available on all processes.<br 
class="newline" />Scope: <span 
class="cmbx-10">global</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 value <span 
class="cmsy-10">-</span>1 <span 
class="cmmi-10">&#x003C;</span>= <span 
class="cmmi-10">root &#x003C;</span>= <span 
class="cmmi-10">np </span><span 
class="cmsy-10">- </span>1, default -1. <br 
class="newline" />
     </dd><dt class="description">
<span 
class="cmbx-10">mode</span> </dt><dd 
class="description">Whether the call is started in non-blocking mode and completed later,
     or is executed synchronously.<br 
class="newline" />Scope: <span 
class="cmbx-10">global</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 value. The action to be taken is determined by
     its bit fields, which can be set with bitwise <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">OR</span></span></span>. Basic action values are
     <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">psb_collective_start_</span></span></span>, <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">psb_collective_end_</span></span></span>. Default: both fields are
     selected (i.e. require synchronous completion).<br 
class="newline" />
                                                                  

                                                                  
     </dd><dt class="description">
<span 
class="cmbx-10">request</span> </dt><dd 
class="description">A request variable to check for operation completion.<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">inout</span>.<br 
class="newline" />If <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">mode</span></span></span> does not specify synchronous completion, then this variable must
     be present.</dd></dl>
<!--l. 895--><p class="indent" >
     <dl class="description"><dt class="description">
<span 
class="cmbx-10">On Return</span> </dt><dd 
class="description">
     </dd><dt class="description">
<span 
class="cmbx-10">dat</span> </dt><dd 
class="description">On destination process(es), the result of the minimum operation.<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">inout</span>.<br 
class="newline" />Specified as: an integer, real or complex variable, which may be a scalar,
     or a rank 1 or 2 array. <br 
class="newline" />Type, kind, rank and size must agree on all processes.
     </dd><dt class="description">
<span 
class="cmbx-10">request</span> </dt><dd 
class="description">A request variable to check for operation completion.<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">inout</span>.<br 
class="newline" />If <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">mode</span></span></span> does not specify synchronous completion, then this variable must
     be present.</dd></dl>
<!--l. 913--><p class="noindent" ><span 
class="cmbx-12">Notes</span>
     <ol  class="enumerate1" >
     <li 
  class="enumerate" id="x82-119002x1">The <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">dat</span></span></span> argument is both input and output, and its value may be changed
     even on processes different from the final result destination.
     </li>
     <li 
  class="enumerate" id="x82-119004x2">The <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">mode</span></span></span> argument can be built with the bitwise <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">IOR()</span></span></span> operator; in the
     following example, the argument is forcing immediate completion, hence the
     <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">request</span></span></span> argument needs not be specified:
     <div class="center" 
>
<!--l. 928--><p class="noindent" >
<div class="minipage"><pre class="verbatim" id="verbatim-85">
&#x00A0;&#x00A0;call&#x00A0;psb_amn(ctxt,dat,mode=ior(psb_collective_start_,psb_collective_end_))
</pre>
<!--l. 932--><p class="nopar" ></div></div>
     </li>
     <li 
  class="enumerate" id="x82-119006x3">When splitting the operation in two calls, the <span class="obeylines-h"><span class="verb"><span 
class="cmtt-10">dat</span></span></span> argument <span 
class="cmti-10">must not </span>be
     accessed between calls:
                                                                  

                                                                  
     <div class="center" 
>
<!--l. 948--><p class="noindent" >
<div class="minipage"><pre class="verbatim" id="verbatim-86">
&#x00A0;&#x00A0;call&#x00A0;psb_amn(ctxt,dat,mode=psb_collective_start_,request=amn_request)
&#x00A0;&#x00A0;.......&#x00A0;!&#x00A0;Do&#x00A0;not&#x00A0;access&#x00A0;dat
&#x00A0;&#x00A0;call&#x00A0;psb_amn(ctxt,dat,mode=psb_collective_end_,request=amn_request)
</pre>
<!--l. 954--><p class="nopar" ></div></div>
     </li></ol>
                                                                  

                                                                  
                                                                  

                                                                  
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