From ab62dc63edac5ac6985ca570dad90a41f135e244 Mon Sep 17 00:00:00 2001 From: abn Date: Wed, 7 Feb 2024 15:13:53 +0100 Subject: [PATCH] [TetraIntersect] Obvious optimisation -> 10% gain by replacing atan2() + use quicker pseudo angle computation suitable for sorting --- src/INTERP_KERNEL/TransformedTriangle.cxx | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/src/INTERP_KERNEL/TransformedTriangle.cxx b/src/INTERP_KERNEL/TransformedTriangle.cxx index 5e1a08606..65ada4f2c 100644 --- a/src/INTERP_KERNEL/TransformedTriangle.cxx +++ b/src/INTERP_KERNEL/TransformedTriangle.cxx @@ -71,8 +71,15 @@ namespace INTERP_KERNEL bool operator()(const double* pt1, const double* pt2) { // calculate angles with the axis - const double ang1 = atan2(pt1[_aIdx] - _a, pt1[_bIdx] - _b); - const double ang2 = atan2(pt2[_aIdx] - _a, pt2[_bIdx] - _b); +// const double ang1 = atan2(pt1[_aIdx] - _a, pt1[_bIdx] - _b); +// const double ang2 = atan2(pt2[_aIdx] - _a, pt2[_bIdx] - _b); + + // A ***much*** faster alternative to atan2 to get a pseudo-angle suitable for sorting: + // https://stackoverflow.com/questions/16542042/fastest-way-to-sort-vectors-by-angle-without-actually-computing-that-angle + const double dy1 = pt1[_aIdx] - _a, dx1 = pt1[_bIdx] - _b, + dy2 = pt2[_aIdx] - _a, dx2 = pt2[_bIdx] - _b; + const double ang1 = std::copysign(1. - dx1/(std::fabs(dx1)+fabs(dy1)),dy1); + const double ang2 = std::copysign(1. - dx2/(std::fabs(dx2)+fabs(dy2)),dy2); return ang1 > ang2; } @@ -690,14 +697,7 @@ namespace INTERP_KERNEL // We keep the test here anyway, to avoid interdependency. // is triangle inclined to x == 0 ? - if(isTriangleInclinedToFacet(OZX)) - { - type = SortOrder::XZ; - } - else //if(isTriangleParallelToFacet(OYZ)) - { - type = SortOrder::YZ; - } + type = isTriangleInclinedToFacet(OZX) ? SortOrder::XZ : SortOrder::YZ; } // create order object -- 2.39.2