Re: d3dx9 [patch 1/3]: Avoid two useless computations

[Rico Schüller]

On 05.04.2013 09:13, Nozomi Kodama wrote:
> s = 0.75f;
> -    if ( order > 2 )
> -        s += 5.0f / 16.0f;
> -    if ( order > 4 )
> -        s -= 3.0f / 32.0f;
> +    if (order > 2)
> +        s = 1.0625f;
> +    if (order > 4)
> +        s = 0.96875f;
>       s /= D3DX_PI;

Doesn't the compiler do that already? If not something like this would 
probably better:

s = 0.23873...f; /* 0.75f / D3DX_PI */
if (order > 2)
	s = 1.0625f / D3DX_PI;
if (order > 4)
	s = 0.96875f / D3DX_PI;

Cheers
Rico

d3dx9 [patch 1/3]: Avoid two useless computations

[Frédéric Delanoy]

On Fri, Apr 5, 2013 at 9:41 AM, Rico Schüller <kgbricola(a)web.de> wrote:
> On 05.04.2013 09:13, Nozomi Kodama wrote:
> > s = 0.75f;
> > -    if ( order > 2 )
> > -        s += 5.0f / 16.0f;
> > -    if ( order > 4 )
> > -        s -= 3.0f / 32.0f;
> > +    if (order > 2)
> > +        s = 1.0625f;
> > +    if (order > 4)
> > +        s = 0.96875f;
> >       s /= D3DX_PI;
>
> Doesn't the compiler do that already?

Most likely,since those are literal constants.
Besides, 5.0f / 16.0f is more readable than a pre-computed result.

So I don't think this patch is really useful.

Frédéric