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A comment on Weird compiler bug – Same code, different results. Parent comment

Re:Weird compiler bug – Same code, different results by jcranmer on Friday January 29, 2021 @06:11PM (#25964061)
They do those optimizations when you enable fast-math flags. Some compilers (e.g., icc) enable those by default. When fast-math is not enabled, then the IEEE 754-violating optimizations are disabled.

Source: I've been working on such optimizations this past week. And that means establishing precisely which flags I need to have enabled in order for optimization to kick in.

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Re:Weird compiler bug – Same code, different results by zaitanz on Friday January 29, 2021 @06:30PM (#25964249)
This is very true. Once upon a time -o3 would enable fast-math. We're very careful to ensure we use test models to verify the outputs of release binaries. Enabling fast-math as you have said optimises the equations in a way that produces different results.
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