]> https://gitweb.dealii.org/ - dealii.git/commitdiff
Improve documentation for allow_check_for_cell_similarity
authorDaniel Arndt <arndtd@ornl.gov>
Tue, 29 Aug 2023 12:33:33 +0000 (08:33 -0400)
committerDaniel Arndt <arndtd@ornl.gov>
Tue, 29 Aug 2023 12:33:33 +0000 (08:33 -0400)
include/deal.II/fe/fe_values_base.h

index 1b275f1ee6d63f6398b2215181c5d2aa7f9702f4..70375e33a4465342dbd3a211b6a5274ee1d61221 100644 (file)
@@ -223,8 +223,14 @@ public:
   virtual ~FEValuesBase() override;
 
   /**
-   * Explicitly allow to check for cell similarity. By default, this is only
-   * enabled when the number of threads is 1.
+   * Explicitly allow to check for cell similarity.
+   * The detection of simple geometries with CellSimilarity is sensitive to the
+   * first cell detected. When using multiple threads, each thread might get a
+   * thread local copy of the FEValues object that is initialized to the first
+   * cell the thread sees. As this cell might be differ between runs and number
+   * of threads used, this slight deviation leads to difference in roundoff
+   * errors that propagate through the program. Therefore, the CellSimilarity
+   * check is disabled by default in case more than one thread is used.
    */
   void
   allow_check_for_cell_similarity(bool allow);

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