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      <title>ITER</title>
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      <div class="title_refTopic" id="xps10_pagetitle">ITER </div>
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      <h4 class="refClassification">Iterative Solver Options </h4>
      <p class="para_refTopic">Defines options for the global iterative solver in SOLs 1, 8, 11, 66, 101, 106, 108, 111, 153 and the element iterative solver in SOLS 1 and 101. </p>
      <div class="title_refCategory">Format: </div>
      <div class="refCategoryContent">
         <table border="1" width="100%" align="center">
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                     <p class="para_th">1 </p>
                  </th>
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                     <p class="para_th">2 </p>
                  </th>
                  <th align="center" colspan="1" rowspan="1">
                     <p class="para_th">3 </p>
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                     <p class="para_th">4 </p>
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                     <p class="para_th">5 </p>
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                     <p class="para_th">6 </p>
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                     <p class="para_th">7 </p>
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                     <p class="para_th">8 </p>
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                     <p class="para_th">9 </p>
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                  <th align="center" colspan="1" rowspan="1">
                     <p class="para_th">10 </p>
                  </th>
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            <tbody>
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                  <td align="left" colspan="1" rowspan="1">
                     <p class="para_td">ITER </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">SID </p>
                  </td>
                  <td align="center" colspan="7" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
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                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="8" rowspan="1">
                     <p class="para_td">OPTION1VALUE1     OPTION2VALUE2     -etc.- </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
            </tbody>
         </table><br></div>
      <div class="title_refCategory">Example: </div>
      <div class="refCategoryContent">
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                  <td align="left" colspan="1" rowspan="1">
                     <p class="para_td">ITER </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">100 </p>
                  </td>
                  <td align="center" colspan="7" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
               </tr>
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                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="center" colspan="8" rowspan="1">
                     <p class="para_td">ITSEPS=1.0E0-7, MSGFLG=YES, PRECOND=BICWELL, IPAD=3 </p>
                  </td>
                  <td align="center" colspan="1" rowspan="1">
                     <p class="para_td">&nbsp; </p>
                  </td>
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      <div class="title_refCategory">Fields:</div>
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                     <p class="para_th"><b class="uiTerm">Field </b></p>
                  </th>
                  <th align="left" colspan="2" rowspan="1">
                     <p class="para_th"><b class="uiTerm">Contents </b></p>
                  </th>
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            <tbody>
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                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">SID </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Set identification number.  (Integer &gt; 0). </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">PRECOND </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Preconditioner option for global and element iterative solution.  (Global default = &ldquo;BIC&rdquo; for real analysis, &ldquo;BICCMPLX&rdquo; for complex analysis and &ldquo;PBDJ&rdquo; for p-version analysis. Element default is to leave option blank)  See Remark <a class="links" href="javascript:void(0)" onclick="top.openFile('QRG/16topic_38.html#refz8Gjq1a4lori');return(false);">56-3</a>. 
                     </p>
                  </td>
               </tr>
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                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Global preconditioner options: </p>
                  </td>
               </tr>
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                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">J </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Jacobi </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">JS </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Jacobi with diagonal scaling. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">C </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Incomplete Cholesky. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CS </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Incomplete Cholesky with diagonal scaling. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">RIC </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Reduced incomplete Cholesky. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">RICS </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Reduced incomplete Cholesky with diagonal scaling. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">PBCJ </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">p-version block Cholesky/Jacobi. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">PBDJ </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">p-version block Direct/Jacobi. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">PBDC </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">p-version block Direct/Cholesky. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">BIC </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Block incomplete Cholesky for real problems. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">BICCMPLX </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Block incomplete Cholesky for complex problems. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">USER </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">User given preconditioning.  For direct frequency response (SOL 108): a decomposition will be done for 1st frequency and the factor will be used for all subsequent frequencies as a preconditioner with the iterative solver.  Other solutions require a DMAP alter.  Please refer to the <em>NX Nastran Numerical Methods User&rsquo;s Guide</em> description of the SOLVIT module. 
                     </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Element preconditioner options: </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">blank </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Standard preconditioning option for element iterative solver (default) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">PRIMAL </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Optional preconditioning option for element iterative solver. This option may produce faster convergence for models which contain a large number of elements with bad aspect ratios. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">CONV </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Convergence criterion.  (Character; Default = &ldquo;AREX&rdquo;) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Global iterative solution: </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">AR </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">||<em>r</em>||/||<em>b</em>|| where r is the residual vector of current iteration and b is the initial load vector; internal criterion. 
                     </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">GE </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Alternative convergence criterion using geometric progression and the differences between two consecutive solution updates; internal criterion. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">AREX </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Same criterion as AR but with the additional consideration of the external convergence criterion.  See Remark <a class="links" href="javascript:void(0)" onclick="top.openFile('QRG/16topic_38.html#refjFAjn2efjuli');return(false);">56-2. </a> (Default). 
                     </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">GEEX </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Same criterion as GE but with the additional consideration of the external convergence criterion.  See Remark <a class="links" href="javascript:void(0)" onclick="top.openFile('QRG/16topic_38.html#refjFAjn2efjuli');return(false);">56-2. </a></p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Element iterative solution: </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">AR </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">For relative reduction in the residual 2-norm. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">GE </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">For relative reduction in the residual preconditioned norm. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">AREX </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">For one of the other or energy norm of error. Also each must fall below a looser stopping threshold (Default). </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">GEEX </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">For relative reduction in the residual infinity norm. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">MSGFLG </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Message flag.  (Character; Default = &ldquo;NO&rdquo;) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">YES </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Messages will be printed for each iteration. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">NO </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Only minimal messages will be printed from the iterative solver (Default). </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">ITSEPS </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">User-given convergence parameter epsilon. (Real&gt;0.0; Default=1.0E-6) (Default=1.0E-8 when the element iterative solver is used.) See remark <a class="links" href="javascript:void(0)" onclick="top.openFile('QRG/16topic_38.html#conv_options');return(false);">56-5</a> for information on setting ITSEPS with the element iterative solver.
                     </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">ITSMAX </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Maximum number of iterations.  (Integer &gt; 0; Default = N/4 where N is the number of rows in the matrix) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">IPAD </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Padding value for RIC, RICS, BIC, and BICCMPLX preconditioning in global iterative solutions. (Integer &gt; 0) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Default = 0 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">for PRECOND = &ldquo;RIC&rdquo; or &ldquo;RICS&rdquo; </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Default = 2 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">for PRECOND = &ldquo;BIC&rdquo; for purely three-dimensional models and three for two-dimensional and mixed element models.  IPAD may be reset automatically by the program to the best value. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Default = 5 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">for PRECOND = &ldquo;BICCMPLX&rdquo;. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">IEXT </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Extraction level in reduced incomplete Cholesky preconditioning in global iterative solution.  Block structuring method in block incomplete Cholesky preconditioning in global iterative solution.  (Integer = 0 thought 7; Default = 0) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">0 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Uses USET/SIL tables (Default). </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">1 - 7 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">The default value of 0 is recommended for all problems.  The values 1 - 7 use a heuristic algorithm with a maximum block size equal to IEXT.  Although setting IEXT to a value other than 0 could lead to slightly improved performance or reduced disk space use, it should be considered exploratory without the expectation of a benefit. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">PREFONLY </p>
                  </td>
                  <td align="left" colspan="2" rowspan="1">
                     <p class="para_td">Specifies early termination of the global iterative solver.  (Integer = 0 or -1; Default = 0) </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">0 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Runs to completion (Default). </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">&nbsp; </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">-1 </p>
                  </td>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">Terminates after preface giving resource estimates. </p>
                  </td>
               </tr>
               <tr>
                  <td align="left" colspan="1" rowspan="1" valign="top">
                     <p class="para_td">ZPIVOT</p>
                  </td>
                  <td align="left" colspan="2" rowspan="1" valign="top">
                     <p class="para_td">Used to adjust the singularity tolerance during the preconditioner phase of an element iterative solution. (Real, Default=1.0E-10)</p>
                  </td>
               </tr>
            </tbody>
         </table><br></div>
      <div class="title_refCategory">Remarks: </div>
      <div class="refCategoryContent">
         <ol type="1" start="1">
            <li>
               <p class="para_item">The global iterative solver is requested by specifying ITER = YES on the NASTRAN statement.  To request the element iterative solver, specify ELEMITER = YES in addition to ITER = YES. The ITER Bulk Data entry is optional and only required to override the defaults specified above.  The ITER Bulk Data entry must be selected by the SMETHOD = SID Case Control command. </p>
            </li>
            <li><a name="refjFAjn2efjuli"></a><p class="para_item">The external epsilon is computed as follows: </p>
               <p class="para_item"><img align="bottom" src="graphics/bulkfgil-equ62.gif" border="0"></p>
               <p class="para_item">where r is the final residual vector, x is the final solution vector and b is the initial load vector (<em>r</em>, <em>x</em>) indicates the inner product of <em>r</em> and <em>x</em> and (<em>b</em>, <em>x</em>) indicates the inner product of <em>b</em> and <em>x</em>. 
               </p>
            </li>
            <li><a name="refz8Gjq1a4lori"></a><p class="para_item">Prior to Version 70.5 of MSC.Nastran, the user had the burden of choosing BICWELL for well conditioned problems and BICILL for ill-conditioned problems.  NX Nastran now determines this automatically.  Thus BICWELL and BICILL are now equivalent to BIC. See &ldquo;Preconditioning Methods&rdquo; in the <em>NX Nastran Numerical Methods User&rsquo;s Guide</em> for more information on these options. 
               </p>
            </li>
            <li>
               <p class="para_item">The restrictions for the element iterative solver are as follows; only available in solution types 1 and 101, does not support superelements, does not support CQUAD8 and TRIA6 elements, CQUAD4 and TRIA3 supported only if K6ROT is defined (results obtained will be the same as if the parameter snorm = 0.0 was entered), DMIG is not supported, inertia relief is not supported, surface-to-surface contact is not supported.</p>
            </li>
            <li><a name="conv_options"></a><p class="para_item">When using the element iterative solver, the convergence tolerance (ITSEPS option) is used to control when the solution terminates. The equation to be solved is:</p>
               <p class="para_item">Kx=b,</p>
               <p class="para_item">let the residual r=b-K(x0)</p>
               <p class="para_item">where x0 is the current solution</p>
               <p class="para_item">The solution stops iterating when the minimum of the following four error measures is below the specified value:</p>
               <ul>
                  <li>
                     <p class="para_item">the relative reduction in the 2&ndash;Norm of the residual (the 2&ndash;Norm of r divided by the 2&ndash;Norm of b)</p>
                  </li>
                  <li>
                     <p class="para_item">The relative reduction in the preconditioned norm of the residual</p>
                  </li>
                  <li>
                     <p class="para_item">the relative reduction in the infinity norm of the residual</p>
                  </li>
                  <li>
                     <p class="para_item">the estimated energy norm of the error</p>
                  </li>
               </ul>
               <p class="para_item">For each error measure, the software also applies a looser tolerance than the tolerance you define here.</p>
               <p class="para_item">This table shows typical results obtained for convergence tolerances:</p>
               <table border="1" cellpadding="2" cellspacing="1" align="center">
                  <colgroup span="1">
                     <col span="1">
                     <col span="1">
                  </colgroup>
                  <tbody>
                     <tr>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">Convergence Tolerance</p>
                        </td>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">Typical Results</p>
                        </td>
                     </tr>
                     <tr>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">1e-5</p>
                        </td>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">Most displacement within 1% accuracy. Unreliable stresses.</p>
                        </td>
                     </tr>
                     <tr>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">1e-6</p>
                        </td>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">All displacements within 1% accuracy. Some stresses off 10&ndash;20%.</p>
                        </td>
                     </tr>
                     <tr>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">1e-7</p>
                        </td>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">Some stresses off as much as 5%.</p>
                        </td>
                     </tr>
                     <tr>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">1e-8</p>
                        </td>
                        <td colspan="1" rowspan="1">
                           <p class="para_td">All stresses (even the small values) within 1%.</p>
                        </td>
                     </tr>
                  </tbody>
               </table><br></li>
         </ol>
      </div>
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