Measure #FLOP of sqrt() function using PAPI.

measure_sqrt_flops.cpp

/*
 * measure_sqrt_flops.cpp
 * Copyright (C) 2013 Keisuke Fukuda
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

// icpc -g -Wall -xHOST -O3 -std=c++0x -funroll-loops -finline-functions -ansi-alias -o measure_sqrt_flops measure_sqrt_flops.cpp -lpapi-lrt

#include <cmath>
#include <cstdlib>
#include <iostream>
#include <vector>

#include <papi.h>

#define ERRCODE(ecode) case ecode : err = #ecode; break

#define PAPI_SAFE_CALL(stmt) do {                 \
    int ret = (stmt);                             \
    if (ret != PAPI_OK) {                         \
      const char *err = "(unknown)";              \
      switch(ret) {                               \
        ERRCODE(PAPI_EATTR);                      \
        ERRCODE(PAPI_EBUF);                       \
        ERRCODE(PAPI_EBUG);                       \
        ERRCODE(PAPI_ECLOST);                     \
        ERRCODE(PAPI_ECMP);                       \
        /*ERRCODE(PAPI_ESBSTR); same value -4 */  \
        ERRCODE(PAPI_ECNFLCT);                    \
        ERRCODE(PAPI_ECOMBO);                     \
        ERRCODE(PAPI_ECOUNT);                     \
        ERRCODE(PAPI_EINVAL);                     \
        ERRCODE(PAPI_EINVAL_DOM);                 \
        ERRCODE(PAPI_EISRUN);                     \
        ERRCODE(PAPI_EMISC);                      \
        ERRCODE(PAPI_ENOCMP);                     \
        ERRCODE(PAPI_ENOCNTR);                    \
        ERRCODE(PAPI_ENOEVNT);                    \
        ERRCODE(PAPI_ENOEVST);                    \
        ERRCODE(PAPI_ENOIMPL);                    \
        ERRCODE(PAPI_ENOINIT);                    \
        ERRCODE(PAPI_ENOMEM);                     \
        ERRCODE(PAPI_ENOSUPP);                    \
        ERRCODE(PAPI_ENOTPRESET);                 \
        ERRCODE(PAPI_ENOTRUN);                    \
        ERRCODE(PAPI_EPERM);                      \
        ERRCODE(PAPI_ESYS);                       \
      }                                           \
      fprintf(stderr,                             \
              "%s:%d :[PAPI] %s failed: %s.\n",   \
              __FILE__, __LINE__, #stmt, err);    \
      exit(-1);                                   \
    }                                             \
  } while(0)                                    


const int NUM_LOOP = 1000000;

typedef float real_t;
// typedef double real_t;

template<typename T> inline T sqrtx(T v);
template<> inline float sqrtx<float>(float v) { return sqrtf(v); }
template<> inline double sqrtx<double>(double v) { return sqrt(v); }

int main() {
    int ret = PAPI_library_init(PAPI_VER_CURRENT);
    if (ret != PAPI_VER_CURRENT) {
        fprintf(stderr, "PAPI_library_init() failed.\n");
        exit(-1);
    }

    int ctrs[] = {PAPI_SP_OPS};
    int num_events = sizeof(ctrs) / sizeof(ctrs[0]);
    int event_set = PAPI_NULL;
    PAPI_SAFE_CALL(PAPI_create_eventset(&event_set));
    PAPI_SAFE_CALL(PAPI_add_events(event_set, ctrs, num_events));

    for (int i = 0; i < 10; i++) {
        volatile real_t d = rand()  * 1.0/ RAND_MAX;

        std::vector<long long> results(num_events, -1L);

        // Start measurement
        PAPI_SAFE_CALL(PAPI_start(event_set));
        {
            volatile real_t d = 1.0;
#pragma unroll
            for(int i=0; i < NUM_LOOP; i++) {
                d += sqrtx(d); // to prevent optimization
            }
        }
        PAPI_SAFE_CALL(PAPI_stop(event_set, results.data()));

        double sp_flop = (double)results[0];
        sp_flop /= NUM_LOOP;
        sp_flop -= 1; // substract 1 FLOP for minus op.
        std::cout << "SP flop of sqrt() : " << sp_flop << std::endl;
    }

    PAPI_SAFE_CALL(PAPI_cleanup_eventset(event_set));
    PAPI_SAFE_CALL(PAPI_destroy_eventset(&event_set));
}