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/*
cpucycles/alpha.c version 20060316
D. J. Bernstein
Public domain.
*/
#include <time.h>
#include <unistd.h>
#include <sys/time.h>
static long long tod(void)
{
struct timeval t;
gettimeofday(&t,(struct timezone *) 0);
return t.tv_sec * (long long) 1000000 + t.tv_usec;
}
static long long rpcc(void)
{
unsigned long long t;
asm volatile("rpcc %0" : "=r"(t));
return t & 0xffffffff;
}
static long long firstrpcc;
static long long firsttod;
static long long lastrpcc;
static long long lasttod;
static double mhz = 0;
static void init(void)
{
firstrpcc = rpcc();
firsttod = tod();
do {
lastrpcc = rpcc();
lasttod = tod();
} while (lasttod - firsttod < 10000);
lastrpcc -= firstrpcc; lastrpcc &= 0xffffffff;
lasttod -= firsttod;
mhz = (double) lastrpcc / (double) lasttod;
}
long long cpucycles_alpha(void)
{
double x;
long long y;
if (!mhz) init();
lastrpcc = rpcc();
lasttod = tod();
lastrpcc -= firstrpcc; lastrpcc &= 0xffffffff;
lasttod -= firsttod;
/* Number of cycles since firstrpcc is lastrpcc + 2^32 y for unknown y. */
/* Number of microseconds since firsttod is lasttod. */
x = (lasttod * mhz - lastrpcc) * 0.00000000023283064365386962890625;
y = x;
while (x > y + 0.5) y += 1;
while (x < y - 0.5) y -= 1;
y *= 4294967296ULL;
lastrpcc += y;
mhz = (double) lastrpcc / (double) lasttod;
return firstrpcc + lastrpcc;
}
long long cpucycles_alpha_persecond(void)
{
if (!mhz) init();
return 1000000.0 * mhz;
}
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