Re: [Mesa-dev] [PATCH] Replace ONE_DIV_LN2 constant with M_LOG2E

2011-05-07 Thread Brian Paul
On Fri, May 6, 2011 at 11:01 AM, Matt Turner matts...@gmail.com wrote:
 1/ln(2) is equivalent to log2(e), so define it as such.

 log2(e) = ln(e)/ln(2) = 1/ln(2)

 Worst of all, the definitions for M_LOG2E and ONE_DIV_LN2
 (right beside each other!) weren't the same.

 Reviewed-by: Alex Deucher alexdeuc...@gmail.com
 Signed-off-by: Matt Turner matts...@gmail.com

I've applied this and the M_PI change.  Thanks.

-Brian
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[Mesa-dev] [PATCH] Replace ONE_DIV_LN2 constant with M_LOG2E

2011-05-06 Thread Matt Turner
1/ln(2) is equivalent to log2(e), so define it as such.

log2(e) = ln(e)/ln(2) = 1/ln(2)

Worst of all, the definitions for M_LOG2E and ONE_DIV_LN2
(right beside each other!) weren't the same.

Reviewed-by: Alex Deucher alexdeuc...@gmail.com
Signed-off-by: Matt Turner matts...@gmail.com
---
 src/mesa/main/compiler.h  |4 
 src/mesa/program/prog_statevars.c |2 +-
 2 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/src/mesa/main/compiler.h b/src/mesa/main/compiler.h
index e17fd0f..81e08a0 100644
--- a/src/mesa/main/compiler.h
+++ b/src/mesa/main/compiler.h
@@ -366,10 +366,6 @@ static INLINE GLuint CPU_TO_LE32(GLuint x)
 #define M_LOG2E (1.4426950408889634074)
 #endif
 
-#ifndef ONE_DIV_LN2
-#define ONE_DIV_LN2 (1.442695040888963456)
-#endif
-
 #ifndef ONE_DIV_SQRT_LN2
 #define ONE_DIV_SQRT_LN2 (1.201122408786449815)
 #endif
diff --git a/src/mesa/program/prog_statevars.c 
b/src/mesa/program/prog_statevars.c
index d94d7fe..16f9690 100644
--- a/src/mesa/program/prog_statevars.c
+++ b/src/mesa/program/prog_statevars.c
@@ -459,7 +459,7 @@ _mesa_fetch_state(struct gl_context *ctx, const 
gl_state_index state[],
  value[0] = (ctx-Fog.End == ctx-Fog.Start)
 ? 1.0f : (GLfloat)(-1.0F / (ctx-Fog.End - ctx-Fog.Start));
  value[1] = ctx-Fog.End * -value[0];
- value[2] = (GLfloat)(ctx-Fog.Density * ONE_DIV_LN2);
+ value[2] = (GLfloat)(ctx-Fog.Density * M_LOG2E); /* M_LOG2E == 
1/ln(2) */
  value[3] = (GLfloat)(ctx-Fog.Density * ONE_DIV_SQRT_LN2);
  return;
 
-- 
1.7.3.4

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