Difference between revisions of "Resequence Command"

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<p>The <code>Resequence</code> command is used to renumber the numbers in an attempt to minimize the bandwidth of the problem. The smaller the bandwidth, the faster will be the FEA calculations. The two options are:</p>
The <tt>Resequence</tt> command is used to renumber the numbers in an attempt to minimize the bandwidth of the problem. The smaller the bandwidth, the faster will be the FEA calculations.
 
== Scripted Input Files ==
 
The two options in scripted input files are
<pre>Resequence #1,#2
Resequence (x),(y)
</pre>


<p>or</p>
or
<pre>Resequence #3
Resequence (id)
</pre>


<p>where</p>
where


<ul>
* (<tt>x</tt>, <tt>y</tt>) define the coordinates (in mm) for a point (or <rr>(R, Z)</rr> coordinates if axisymmetric). The resequencing will start at the one node nearest to that point.
* <tt>(id)</tt> is a previously defined [[Keypoint Command|keypoint]]. The resequencing will start at the node at that keypoint.


<li>(#1, #2) define <code>(x, y)</code> coordinates (in mm) for a point (or <code>(R, Z)</code> if axisymmetric). The resequencing will start at the one node nearest to that point.</li>
== XML Input Files ==


<li>#3 is a previously defined <a href="keypoint.html">key point</a>. The resequencing will start at the node at that key point.</li>
In <tt>XML<tt> files, the two options, which must be within the <tt><GridBCs</tt> element, are:


</ul>
<Resequence x='(x)' y='(y)'/>


<h2>Notes</h2>
or
 
<ol>
<Resequence keypt='(id)'/>
 
<li>It is best to start the resequencing at a node on the boundary of the object and probably on a corner. The final bandwidth may depend on the node selected for resequencing. The bandwidth is report in FEA output results. You can vary the resequencing node to find the minimum value.</li>
 
<li>Another use of this command is to verify mesh connectivity. Since disconnected sections of a static FEA mesh will cause a singular stiffness matrix, the calculations will fail. This command will find such connectivity problems before the calculations start.</li>
 
<li>The algorithm used to resequence the nodes in described in a paper by <a href="../references.html#Gibbs1976">Gibbs, Poole, and Stockmeyer (1976)</a>.</li>


<li>The <code>Resequencing</code> command should come after the other <a href="definemesh.html">meshing commands</a> are done</li>
where <tt>(x)</tt>, <tt>(x)</tt>, and <tt>(id)</tt> are the same as define [[#Scripted Input Files|above]].


<li>The <code>Resequence</code> command is only allowed for <a href="analysis.html">FEA analyses</a>.</li>
== Notes ==


</ol>
# It is best to start the resequencing at a node on the boundary of the object and probably on a corner. The final bandwidth may depend on the node selected for resequencing. The bandwidth is reported in FEA output results. You can vary the resequencing node to find the minimum value.
# Another use of this command is to verify mesh connectivity. Since disconnected sections of a static FEA mesh will cause a singular stiffness matrix, the calculations will fail. This command will find such connectivity problems before the calculations start.
# The algorithm used to resequence the nodes in described in a paper by Gibbs, Poole, and Stockmeyer.<ref name='RS'>N. E. Gibbs, W. G. Poole, and P. K. Stockmeyer, "An Algorithm for Reducing the Bandwidth and Profile of a Sparse Matrix," <i>SIAM Journal of Numerical Analysis</i>, <b>13</b>, 236-250 (1976).</ref>
# In scripted files, The <tt>Resequencing</t> command should come after the other <a href="definemesh.html">meshing commands</a> are done</li>

Revision as of 21:34, 10 September 2013

The Resequence command is used to renumber the numbers in an attempt to minimize the bandwidth of the problem. The smaller the bandwidth, the faster will be the FEA calculations.

Scripted Input Files

The two options in scripted input files are

Resequence (x),(y)

or

Resequence (id)

where

  • (x, y) define the coordinates (in mm) for a point (or <rr>(R, Z)</rr> coordinates if axisymmetric). The resequencing will start at the one node nearest to that point.
  • (id) is a previously defined keypoint. The resequencing will start at the node at that keypoint.

XML Input Files

In XML files, the two options, which must be within the <GridBCs element, are:

<Resequence x='(x)' y='(y)'/>

or

<Resequence keypt='(id)'/>

where (x), (x), and (id) are the same as define above.

Notes

  1. It is best to start the resequencing at a node on the boundary of the object and probably on a corner. The final bandwidth may depend on the node selected for resequencing. The bandwidth is reported in FEA output results. You can vary the resequencing node to find the minimum value.
  2. Another use of this command is to verify mesh connectivity. Since disconnected sections of a static FEA mesh will cause a singular stiffness matrix, the calculations will fail. This command will find such connectivity problems before the calculations start.
  3. The algorithm used to resequence the nodes in described in a paper by Gibbs, Poole, and Stockmeyer.[1]
  4. In scripted files, The Resequencing</t> command should come after the other <a href="definemesh.html">meshing commands</a> are done
  1. N. E. Gibbs, W. G. Poole, and P. K. Stockmeyer, "An Algorithm for Reducing the Bandwidth and Profile of a Sparse Matrix," SIAM Journal of Numerical Analysis, 13, 236-250 (1976).