[IPOL discuss] Fast DCT using FFTW3

[Pascal Monasse]

Hi Miguel,

> It even analyzes the numerical expressions and tries to compute it the
> shorter and faster way.
> For example, if y = f(y) + 2*f(y) + 3*f(y), it doesn't call f(y) three
> times.

I doubt that the compiler would dare such an aggressive optimization. f may 
have side effects that the compiler is not able to analyze, therefore it may 
think it is safer to call f(y) three times...

Best,
Pascal