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/*******************************************************************************
* Copyright (c) 2006 International Business Machines Corporation. *
* All rights reserved. This program and the accompanying materials *
* are made available under the terms of the Common Public License v1.0 *
* which accompanies this distribution, and is available at *
* http://www.opensource.org/licenses/cpl1.0.php *
* *
* Contributors: *
* Douglas M. Pase - initial API and implementation *
*******************************************************************************/
//
// Configuration
//
// Implementation header
#include "timer.h"
// System includes
#include <cstdio>
#include <sys/time.h>
static int64 read_rtc();
static void calibrate_rtc(int n);
static double wall_seconds();
static int wall_ticks = -1;
static int rtc_ticks = -1;
static double wall_elapsed = -1;
static int64 rtc_elapsed = -1;
static double time_factor = -1;
#if !defined(RTC) && !defined(GTOD)
#define RTC
#endif
//
// Implementation
//
#if defined(RTC)
double Timer::seconds() {
return (double) read_rtc() * time_factor;
}
int64 Timer::ticks() {
// See pg. 406 of the AMD x86-64 Architecture
// Programmer's Manual, Volume 2, System Programming
unsigned int eax = 0, edx = 0;
__asm__ __volatile__(
"rdtsc ;"
"movl %%eax,%0;"
"movl %%edx,%1;"
""
: "=r"(eax), "=r"(edx)
:
: "%eax", "%edx"
);
return ((int64) edx << 32) | (int64) eax;
}
static int64 read_rtc() {
// See pg. 406 of the AMD x86-64 Architecture
// Programmer's Manual, Volume 2, System Programming
unsigned int eax = 0, edx = 0;
__asm__ __volatile__(
"rdtsc ;"
"movl %%eax,%0;"
"movl %%edx,%1;"
""
: "=r"(eax), "=r"(edx)
:
: "%eax", "%edx"
);
return ((int64) edx << 32) | (int64) eax;
}
void Timer::calibrate() {
Timer::calibrate(1000);
}
void Timer::calibrate(int n) {
wall_ticks = n;
double wall_start, wall_finish, t;
t = wall_seconds();
while (t == (wall_start = wall_seconds())) {
;
}
int64 rtc_start = read_rtc();
for (int i = 0; i < wall_ticks; i++) {
t = wall_seconds();
while (t == (wall_finish = wall_seconds())) {
;
}
}
int64 rtc_finish = read_rtc();
wall_elapsed = wall_finish - wall_start;
rtc_elapsed = rtc_finish - rtc_start;
time_factor = wall_elapsed / (double) rtc_elapsed;
}
static double wall_seconds() {
struct timeval t;
gettimeofday(&t, NULL);
return (double) t.tv_sec + (double) t.tv_usec * 1E-6;
}
#else
double
Timer::seconds()
{
struct timeval t;
gettimeofday(&t, NULL);
return (double) t.tv_sec + (double) t.tv_usec * 1E-6;
}
int64
Timer::ticks()
{
struct timeval t;
gettimeofday(&t, NULL);
return 1000000 * (int64) t.tv_sec + (int64) t.tv_usec;
}
void
Timer::calibrate()
{
}
void
Timer::calibrate(int n)
{
}
#endif
static double min(double v1, double v2) {
if (v2 < v1)
return v2;
return v1;
}
double Timer::resolution() {
double a, b, c = 1E9;
for (int i = 0; i < 10; i++) {
a = Timer::seconds();
while (a == (b = Timer::seconds()))
;
a = Timer::seconds();
while (a == (b = Timer::seconds()))
;
c = min(b - a, c);
}
return c;
}
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