[Mesa-dev] [PATCH] Improve ONE_DIV_LN2 and M_PI constants

[Alex Deucher]

On Wed, May 4, 2011 at 3:25 PM, Matt Turner <mattst88 at gmail.com> wrote:
> On Thu, Dec 2, 2010 at 8:20 PM, Matt Turner <mattst88 at gmail.com> wrote:
>> On Wed, Dec 1, 2010 at 11:24 PM, Ian Romanick <idr at freedesktop.org> wrote:
>>> On 12/01/2010 01:40 PM, Matt Turner wrote:
>>>> 1/ln(2) is equivalent to log2(e), so define it as such.
>>>>
>>>> log2(e) = ln(e)/ln(2) = 1/ln(2)
>>>>
>>>> M_PI is updated to add some precision (value found in my math.h header).
>>>
>>> I wish I had noticed this when I added M_LOG2E.  It seems better to
>>> replace the single use of ONE_DIV_LN2 (in prog_statevars.c) with M_LOG2E.
>>
>> I think replacing ONE_DIV_LN2 with M_LOG2E in its single use makes the
>> code harder to understand, especially since the next line is
>>
>> value[2] = (GLfloat)(ctx->Fog.Density * ONE_DIV_LN2);
>> value[3] = (GLfloat)(ctx->Fog.Density * ONE_DIV_SQRT_LN2);
>>
>> It's not intuitively obvious that M_LOG2E == 1/ln(2), so I actually
>> think the patch is good as is.
>>
>> Matt
>
> I never saw any response, so how about the two attached patches?

They look fine to me.

Reviewed-by: Alex Deucher <alexdeucher at gmail.com>

>
> Matt
>
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