From 2252d481d66ddc3462acbd7473d9a1d4702b64ee Mon Sep 17 00:00:00 2001 From: Andreas Neustifter Date: Wed, 2 Sep 2009 14:03:11 +0000 Subject: [PATCH] Sort edges in MaximumSpanningTree more stable in case of equal weight. (See http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20090824/085890.html) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80789 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Instrumentation/MaximumSpanningTree.cpp | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/lib/Transforms/Instrumentation/MaximumSpanningTree.cpp b/lib/Transforms/Instrumentation/MaximumSpanningTree.cpp index 80f1a15d632..ffd100e0533 100644 --- a/lib/Transforms/Instrumentation/MaximumSpanningTree.cpp +++ b/lib/Transforms/Instrumentation/MaximumSpanningTree.cpp @@ -30,7 +30,11 @@ namespace { const ProfileInfo::EdgeWeight Y) const { if (X.second > Y.second) return true; if (X.second < Y.second) return false; -#ifndef NDEBUG + + // It would be enough to just compare the weights of the edges and be + // done. With edges of the same weight this may lead to a different MST + // each time the MST is created. To have more stable sorting (and thus + // more stable MSTs) furhter sort the edges. if (X.first.first != 0 && Y.first.first == 0) return true; if (X.first.first == 0 && Y.first.first != 0) return false; if (X.first.first == 0 && Y.first.first == 0) return false; @@ -44,7 +48,7 @@ namespace { if (X.first.second->size() > Y.first.second->size()) return true; if (X.first.second->size() < Y.first.second->size()) return false; -#endif + return false; } };