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/*
* fcyc.c - Estimate the time (in CPU cycles) used by a function f
*
* Copyright (c) 2002, R. Bryant and D. O'Hallaron, All rights reserved.
* May not be used, modified, or copied without permission.
*
* Uses the cycle timer routines in clock.c to estimate the
* the time in CPU cycles for a function f.
*/
#include <stdlib.h>
#include <sys/times.h>
#include <stdio.h>
#include "fcyc.h"
#include "clock.h"
/* Default values */
#define K 3 /* Value of K in K-best scheme */
#define MAXSAMPLES 20 /* Give up after MAXSAMPLES */
#define EPSILON 0.01 /* K samples should be EPSILON of each other*/
#define COMPENSATE 0 /* 1-> try to compensate for clock ticks */
#define CLEAR_CACHE 0 /* Clear cache before running test function */
#define CACHE_BYTES (1<<19) /* Max cache size in bytes */
#define CACHE_BLOCK 32 /* Cache block size in bytes */
static int kbest = K;
static int maxsamples = MAXSAMPLES;
static double epsilon = EPSILON;
static int compensate = COMPENSATE;
static int clear_cache = CLEAR_CACHE;
static int cache_bytes = CACHE_BYTES;
static int cache_block = CACHE_BLOCK;
static int *cache_buf = NULL;
static double *values = NULL;
static int samplecount = 0;
/* for debugging only */
#define KEEP_VALS 0
#define KEEP_SAMPLES 0
#if KEEP_SAMPLES
static double *samples = NULL;
#endif
/*
* init_sampler - Start new sampling process
*/
static void init_sampler()
{
if (values)
free(values);
values = calloc(kbest, sizeof(double));
#if KEEP_SAMPLES
if (samples)
free(samples);
/* Allocate extra for wraparound analysis */
samples = calloc(maxsamples+kbest, sizeof(double));
#endif
samplecount = 0;
}
/*
* add_sample - Add new sample
*/
static void add_sample(double val)
{
int pos = 0;
if (samplecount < kbest) {
pos = samplecount;
values[pos] = val;
} else if (val < values[kbest-1]) {
pos = kbest-1;
values[pos] = val;
}
#if KEEP_SAMPLES
samples[samplecount] = val;
#endif
samplecount++;
/* Insertion sort */
while (pos > 0 && values[pos-1] > values[pos]) {
double temp = values[pos-1];
values[pos-1] = values[pos];
values[pos] = temp;
pos--;
}
}
/*
* has_converged- Have kbest minimum measurements converged within epsilon?
*/
static int has_converged()
{
return
(samplecount >= kbest) &&
((1 + epsilon)*values[0] >= values[kbest-1]);
}
/*
* clear - Code to clear cache
*/
static volatile int sink = 0;
static void clear()
{
int x = sink;
int *cptr, *cend;
int incr = cache_block/sizeof(int);
if (!cache_buf) {
cache_buf = malloc(cache_bytes);
if (!cache_buf) {
fprintf(stderr, "Fatal error. Malloc returned null when trying to clear cache\n");
exit(1);
}
}
cptr = (int *) cache_buf;
cend = cptr + cache_bytes/sizeof(int);
while (cptr < cend) {
x += *cptr;
cptr += incr;
}
sink = x;
}
/*
* fcyc - Use K-best scheme to estimate the running time of function f
*/
double fcyc(test_funct f, void *argp)
{
double result;
init_sampler();
if (compensate) {
do {
double cyc;
if (clear_cache)
clear();
start_comp_counter();
f(argp);
cyc = get_comp_counter();
add_sample(cyc);
} while (!has_converged() && samplecount < maxsamples);
} else {
do {
double cyc;
if (clear_cache)
clear();
start_counter();
f(argp);
cyc = get_counter();
add_sample(cyc);
} while (!has_converged() && samplecount < maxsamples);
}
#ifdef DEBUG
{
int i;
printf(" %d smallest values: [", kbest);
for (i = 0; i < kbest; i++)
printf("%.0f%s", values[i], i==kbest-1 ? "]\n" : ", ");
}
#endif
result = values[0];
#if !KEEP_VALS
free(values);
values = NULL;
#endif
return result;
}
/*************************************************************
* Set the various parameters used by the measurement routines
************************************************************/
/*
* set_fcyc_clear_cache - When set, will run code to clear cache
* before each measurement.
* Default = 0
*/
void set_fcyc_clear_cache(int clear)
{
clear_cache = clear;
}
/*
* set_fcyc_cache_size - Set size of cache to use when clearing cache
* Default = 1<<19 (512KB)
*/
void set_fcyc_cache_size(int bytes)
{
if (bytes != cache_bytes) {
cache_bytes = bytes;
if (cache_buf) {
free(cache_buf);
cache_buf = NULL;
}
}
}
/*
* set_fcyc_cache_block - Set size of cache block
* Default = 32
*/
void set_fcyc_cache_block(int bytes) {
cache_block = bytes;
}
/*
* set_fcyc_compensate- When set, will attempt to compensate for
* timer interrupt overhead
* Default = 0
*/
void set_fcyc_compensate(int compensate_arg)
{
compensate = compensate_arg;
}
/*
* set_fcyc_k - Value of K in K-best measurement scheme
* Default = 3
*/
void set_fcyc_k(int k)
{
kbest = k;
}
/*
* set_fcyc_maxsamples - Maximum number of samples attempting to find
* K-best within some tolerance.
* When exceeded, just return best sample found.
* Default = 20
*/
void set_fcyc_maxsamples(int maxsamples_arg)
{
maxsamples = maxsamples_arg;
}
/*
* set_fcyc_epsilon - Tolerance required for K-best
* Default = 0.01
*/
void set_fcyc_epsilon(double epsilon_arg)
{
epsilon = epsilon_arg;
}