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libc/match: Use of exp() vs expf() in logf() caused function to be slow.

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This commit is contained in:
Alan Carvalho de Assis 2017-10-19 09:14:34 -06:00 committed by Gregory Nutt
parent 1182702b80
commit 0ef127e273
2 changed files with 22 additions and 12 deletions
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19
libc/math/lib_logf.c
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@ -3,7 +3,7 @@
* *
* This file is a part of NuttX: * This file is a part of NuttX:
* *
* Copyright (C) 2012 Gregory Nutt. All rights reserved. * Copyright (C) 2012, 2017 Gregory Nutt. All rights reserved.
* Ported by: Darcy Gong * Ported by: Darcy Gong
* *
* It derives from the Rhombus OS math library by Nick Johnson which has * It derives from the Rhombus OS math library by Nick Johnson which has
@ -38,19 +38,26 @@
* Public Functions * Public Functions
****************************************************************************/ ****************************************************************************/
/****************************************************************************
* Name: logf
****************************************************************************/
float logf(float x) float logf(float x)
{ {
float y, y_old, ey, epsilon; float y;
float y_old;
float ey;
float epsilon;
y = 0.0F; y = 0.0F;
y_old = 1.0F; y_old = 1.0F;
epsilon = FLT_EPSILON; epsilon = FLT_EPSILON;
while (y > y_old + epsilon || y < y_old - epsilon) while (y > y_old + epsilon || y < y_old - epsilon)
{ {
y_old = y; y_old = y;
ey = exp(y); ey = expf(y);
y -= (ey - x) / ey; y -= (ey - x) / ey;
if (y > FLT_MAX_EXP_X) if (y > FLT_MAX_EXP_X)
{ {

15
libc/math/lib_logl.c
View File

@ -3,7 +3,7 @@
* *
* This file is a part of NuttX: * This file is a part of NuttX:
* *
* Copyright (C) 2012 Gregory Nutt. All rights reserved. * Copyright (C) 2012, 2017 Gregory Nutt. All rights reserved.
* Ported by: Darcy Gong * Ported by: Darcy Gong
* *
* It derives from the Rhombus OS math library by Nick Johnson which has * It derives from the Rhombus OS math library by Nick Johnson which has
@ -42,17 +42,20 @@
#ifdef CONFIG_HAVE_LONG_DOUBLE #ifdef CONFIG_HAVE_LONG_DOUBLE
long double logl(long double x) long double logl(long double x)
{ {
long double y, y_old, ey, epsilon; long double y;
long double y_old;
long double ey;
long double epsilon;
y = 0.0; y = 0.0;
y_old = 1.0; y_old = 1.0;
epsilon = LDBL_EPSILON; epsilon = LDBL_EPSILON;
while (y > y_old + epsilon || y < y_old - epsilon) while (y > y_old + epsilon || y < y_old - epsilon)
{ {
y_old = y; y_old = y;
ey = expl(y); ey = expl(y);
y -= (ey - x) / ey; y -= (ey - x) / ey;
if (y > 700.0) if (y > 700.0)
{ {