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Issue #11888: Use system log2() when available 

I expect the system libc to use more accurate functions than Python. The GNU
libc uses for example FYL2X and FYL2XP1 hardware instructions on Intel FPU.
This commit is contained in:
Victor Stinner 2011-05-09 12:45:41 +02:00
parent 936d518dc8
commit 8f9f8d612a
4 changed files with 10 additions and 3 deletions
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4
Modules/mathmodule.c
View File

@ -602,6 +602,9 @@ m_log2(double x)
} }
if (x > 0.0) { if (x > 0.0) {
#ifdef HAVE_LOG2
return log2(x);
#else
double m; double m;
int e; int e;
m = frexp(x, &e); m = frexp(x, &e);
@ -617,6 +620,7 @@ m_log2(double x)
else { else {
return log(m) / log(2.0) + e; return log(m) / log(2.0) + e;
} }
#endif
} }
else if (x == 0.0) { else if (x == 0.0) {
errno = EDOM; errno = EDOM;

2
configure vendored
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@ -11864,7 +11864,7 @@ _ACEOF
fi fi
done done
for ac_func in hypot lgamma log1p round tgamma for ac_func in hypot lgamma log1p log2 round tgamma
do : do :
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh` as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var" ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"

4
configure.in
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@ -2512,7 +2512,7 @@ AC_CHECK_FUNCS(alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
futimens futimes \ futimens futimes \
gai_strerror getgroups getlogin getloadavg getpeername getpgid getpid \ gai_strerror getgroups getlogin getloadavg getpeername getpgid getpid \
getpriority getresuid getresgid getpwent getspnam getspent getsid getwd \ getpriority getresuid getresgid getpwent getspnam getspent getsid getwd \
initgroups kill killpg lchmod lchown lockf linkat lstat lutimes mbrtowc mkdirat mkfifo \ initgroups kill killpg lchmod lchown lockf log2 linkat lstat lutimes mbrtowc mkdirat mkfifo \
mkfifoat mknod mknodat mktime mremap nice openat pathconf pause plock poll \ mkfifoat mknod mknodat mktime mremap nice openat pathconf pause plock poll \
posix_fallocate posix_fadvise pread \ posix_fallocate posix_fadvise pread \
pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath renameat \ pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath renameat \
@ -3368,7 +3368,7 @@ LIBS_SAVE=$LIBS
LIBS="$LIBS $LIBM" LIBS="$LIBS $LIBM"
AC_CHECK_FUNCS([acosh asinh atanh copysign erf erfc expm1 finite gamma]) AC_CHECK_FUNCS([acosh asinh atanh copysign erf erfc expm1 finite gamma])
AC_CHECK_FUNCS([hypot lgamma log1p round tgamma]) AC_CHECK_FUNCS([hypot lgamma log1p log2 round tgamma])
AC_CHECK_DECLS([isinf, isnan, isfinite], [], [], [[#include <math.h>]]) AC_CHECK_DECLS([isinf, isnan, isfinite], [], [], [[#include <math.h>]])
# On FreeBSD 6.2, it appears that tanh(-0.) returns 0. instead of # On FreeBSD 6.2, it appears that tanh(-0.) returns 0. instead of

3
pyconfig.h.in
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@ -476,6 +476,9 @@
/* Define to 1 if you have the `log1p' function. */ /* Define to 1 if you have the `log1p' function. */
#undef HAVE_LOG1P #undef HAVE_LOG1P
/* Define to 1 if you have the `log2' function. */
#undef HAVE_LOG2
/* Define this if you have the type long double. */ /* Define this if you have the type long double. */
#undef HAVE_LONG_DOUBLE #undef HAVE_LONG_DOUBLE