Math Performance(exp)

[Gordan Bobic]

Why not use:

expf(myFloat);

That's what it's for.

On Thu, 20 Sep 2007, Blankenship, David wrote:

> I am calling the exp function in a tight loop, a little over 238 million
> times. As expected, it takes a while, but it seemed to take longer than
> necessary, so I was looking into this. What I found was that if I call
> exp as I am with a single precision floating point value:
>
> exp( myFloat );
>
> it takes a long time, but if I cast my single precision value to a
> double:
>
> exp( double(myFloat) );
>
> it takes about 1/3 of the time to execute. This is fantastic, but I need
> to know why this works so I can fix my code to use this as well as
> updating any other code that might benefit from this change.