[dahart]

That’s fair. Ideally transitive dependencies should be completely hidden from you. Hopefully the author of the library you include directly has heeded the instructions of libraries they depend on.

Hey I grant and acknowledge that using fast-math carries a little risk of surprises, we don’t necessarily need to try to think of corner cases. I’m mostly pushing back a little because using floats at all carries almost as much risk. A lot of people seem to use floats without knowing how inaccurate floats are, and a lot of people aren’t doing precision analysis or handling the exceptional cases… and don’t really need to.

[ska]

> A lot of people seem to use floats without knowing how inaccurate floats are,

Small nit, but floats aren't inaccurate, they have non uniform precision. Some float operations can be inaccurate, but that's rather path dependent...

One problem with -ffast-math is that a) it sounds appealing and b) people don't understand floats, so lots of people turn it on without understanding what it does, and that can introduce subtle problems in code they didn't write.

Sometimes in computational code it makes sense e.g. to get rid of denorms, but a very small fraction of programmers understand this properly, or ever will.

I wish they had named it something scary sounding.

[account42]

> Sometimes in computational code it makes sense e.g. to get rid of denorms, but a very small fraction of programmers understand this properly, or ever will.

"Some times" here being almost all the time. It is rare that your code will break without denormals if it doesn't already have precision problems with them.

[dahart]

I am talking about float operations, of course. And they’re all inaccurate, generally speaking, because they round. Fast math rounding error is not much larger than rounding error without fast mast.