ldexp and frexp benchmark between Mir, C and Phobos

Guillaume Piolat first.last at gmail.com
Wed Jan 2 14:05:04 UTC 2019

On Wednesday, 2 January 2019 at 09:35:39 UTC, kinke wrote:
> On Tuesday, 1 January 2019 at 23:36:55 UTC, Guillaume Piolat 
> wrote:
>> llvm_exp (defers to C runtime) gives considerable speed 
>> improvement over `std.math.exp`.
> My tests back then on Linux also showed new `exp(float)` being 
> about half as fast as C, while the double-version was somehow 
> 4x faster.

Interesting. At least the VS runtime seems to have different code 
for `exp(float)` and `exp(double)`. This could be an explanation.

> Then look at the implementation of exp() and you'll see that it 
> uses ldexp() once. So by porting Ilya's version (or the Cephes 
> one) to Phobos, I'm sure we can match the C speed for 
> single-precision too.

Good idea.

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