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# ===========================================================================
# http://www.gnu.org/software/autoconf-archive/ax_cpu_freq.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_CPU_FREQ
#
# DESCRIPTION
#
# Compute the CPU frequency and define CPU_FREQ accordingly.
#
# LICENSE
#
# Copyright (c) 2008 Christophe Tournayre <turn3r@users.sourceforge.net>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 7
AC_DEFUN([AX_CPU_FREQ],
[AC_REQUIRE([AC_PROG_CC])
AC_LANG_PUSH([C++])
AC_CACHE_CHECK(your cpu frequency, ax_cpu_freq,
[AC_RUN_IFELSE([AC_LANG_PROGRAM([
#include <iostream>
#include <sys/time.h>
#include <fstream>
using namespace std;
static __inline__ unsigned long long int rdtsc()
{
unsigned long long int x;
__asm__ volatile (".byte 0x0f, 0x31":"=A" (x));
return x;
}
static float estimate_MHz(long sleeptime = 250000)
{
struct timezone tz;
struct timeval tvstart, tvstop;
unsigned long long int cycles[[2]];
float microseconds;
double freq = 1.0f;
memset(&tz, 0, sizeof(tz));
gettimeofday(&tvstart, &tz);
cycles[[0]] = rdtsc();
gettimeofday(&tvstart, &tz);
usleep(sleeptime);
gettimeofday(&tvstop, &tz);
cycles[[1]] = rdtsc();
gettimeofday(&tvstop, &tz);
microseconds = (tvstop.tv_sec - tvstart.tv_sec) * 1000000 +
(tvstop.tv_usec - tvstart.tv_usec);
return (float) (cycles[[1]] - cycles[[0]]) / (microseconds / freq);
}
static float average_MHz(int tries = 2)
{
float frequency = 0;
for (int i = 1; i <= tries; i++)
frequency += estimate_MHz(i * 150000);
if (tries > 0)
return frequency / (float) tries;
else
return 0;
}
], [
ofstream of("conftest_cpufreq");
if(of.is_open())
of << average_MHz();
else
return 1;
of.close()
])],
[ax_cpu_freq=`cat conftest_cpufreq`; rm -f conftest_cpufreq],
[ax_cpu_freq=unknow; rm -f conftest_cpufreq]
)])
AC_LANG_POP([C++])
AC_DEFINE_UNQUOTED([CPU_FREQ], ${ax_cpu_freq}, [The cpu frequency (in MHz)])
])
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