From 6d1107d24181eb33d2cb5581383ded52af0d469a Mon Sep 17 00:00:00 2001 From: Daniel Arndt Date: Tue, 29 Aug 2023 08:33:33 -0400 Subject: [PATCH] Improve documentation for allow_check_for_cell_similarity --- include/deal.II/fe/fe_values_base.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/include/deal.II/fe/fe_values_base.h b/include/deal.II/fe/fe_values_base.h index 1b275f1ee6..70375e33a4 100644 --- a/include/deal.II/fe/fe_values_base.h +++ b/include/deal.II/fe/fe_values_base.h @@ -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); -- 2.39.5