https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104251
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Felix Köhler from comment #0) > According to cppreference.com: > "The behavior is non-deterministic if binary_op is not associative or not > commutative. ... in other words, reduce behaves like std::accumulate except > the elements of the range may be grouped and rearranged in arbitrary order." > which seems to support the CLANG interpretation. I think you read this wrong. this wording says it supports both. That is: If we have 1,2,3,1: it can be done as: (1 op 2) op (3 op 1) or ((1 op 2) op 3) op 1 Or really any order or grouping.
