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Fix bug in logf() algorithm that caused erroneous INFINITY results.

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This commit is contained in:
David Alessio 2016-07-14 20:15:37 -06:00 committed by Gregory Nutt
parent 18059d6821
commit 912ad2d345
2 changed files with 10 additions and 7 deletions
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3
libc/math/lib_erf.c
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@ -67,6 +67,7 @@ double erf(double x)
sign = (x >= 0 ? 1 : -1); sign = (x >= 0 ? 1 : -1);
t = 1.0/(1.0 + p*x); t = 1.0/(1.0 + p*x);
return sign * (1.0 - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t * expf(-x * x)); return sign * (1.0 - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t *
(double)expf(-x * x));
} }
#endif #endif

14
libc/math/lib_logf.c
View File

@ -32,6 +32,8 @@
#include <math.h> #include <math.h>
#include <float.h> #include <float.h>
#define FLT_MAX_EXP_X 88.0F
/**************************************************************************** /****************************************************************************
* Public Functions * Public Functions
****************************************************************************/ ****************************************************************************/
@ -50,25 +52,25 @@ float logf(float x)
ey = exp(y); ey = exp(y);
y -= (ey - x) / ey; y -= (ey - x) / ey;
if (y > 700.0F) if (y > FLT_MAX_EXP_X)
{ {
y = 700.0F; y = FLT_MAX_EXP_X;
} }
if (y < -700.0F) if (y < -FLT_MAX_EXP_X)
{ {
y = -700.0F; y = -FLT_MAX_EXP_X;
} }
epsilon = (fabsf(y) > 1.0F) ? fabsf(y) * FLT_EPSILON : FLT_EPSILON; epsilon = (fabsf(y) > 1.0F) ? fabsf(y) * FLT_EPSILON : FLT_EPSILON;
} }
if (y == 700.0F) if (y == FLT_MAX_EXP_X)
{ {
return INFINITY; return INFINITY;
} }
if (y == -700.0F) if (y == -FLT_MAX_EXP_X)
{ {
return INFINITY; return INFINITY;
} }