https://ascend4.org/index.php?action=history&feed=atom&title=Checking_models 2026-05-03T16:54:51Z Revision history for this page on the wiki MediaWiki 1.43.6 https://ascend4.org/index.php?title=Checking_models&diff=117&oldid=prev 2010-05-13T13:53:14Z

<p>Restored page from Google Cache, uploaded by John Pye</p> <p><b>New page</b></p><div>&lt;div&gt;&#039;&#039;This article is incomplete or needs expanding. Please help out by adding your comments.&#039;&#039;&lt;/div&gt;<br /> <br /> ASCEND includes a number of features for &#039;&#039;&#039;checking&#039;&#039;&#039; that a model is correctly written. Currently the following checks are performed.<br /> <br /> <br /> == Instance check ==<br /> <br /> Firstly, the model&#039;s instance tree is checked for integrity. Instances are checked for being of the correct type, un-executed statements are searched for, correct parent-child relationships are verified and [[Cliques]] are checked for containing items of identical type. The function &lt;tt&gt;RecursiveCheckInstance&lt;/tt&gt; in {{src|ascend/compiler/check.c}} does the hard work for this one.<br /> <br /> <br /> == Degrees of freedom check ==<br /> <br /> The degrees of freedom check tests to see if a model is underspecified (too many unknown variables, not enough equations) or overspecified (too many equations, not enough free variables), or structurally singular. The code in the file {{src|ascend/solver/slvDOF.c}}, together with the functions &lt;tt&gt;mtx_output_assign&lt;/tt&gt; and &lt;tt&gt;mtx_symbolic_rank&lt;/tt&gt; from {{src|ascend/linear/mtx_perms.c}} do this work.<br /> <br /> A structurally singular system is one which has the variables and equations arranged in such a way that it is impossible to develop a strategy for solving them.<br /> <br /> <br /> <br /> <br /> [[Category:Incomplete]]<br /> [[Category:Documentation]]</div>

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