papi_br_prc.c

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/* This file attempts to test the predicted correctly branches  */
/* performance event as counted by PAPI_BR_PRC          */

/* Ideally this event should measure                */
/*  predicted correctly *conditional* branches      */

/* If that's not available, then use total branches.        */

/* by Vince Weaver, <vincent.weaver@maine.edu>          */


#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>

#include "papi.h"
#include "papi_test.h"

#include "display_error.h"
#include "testcode.h"



int main(int argc, char **argv) {

    int num_runs=100,i;
    int num_random_branches=500000;
    long long high=0,low=0,average=0,expected=1500000;
    long long expected_high,expected_low;

    long long count,total=0;
    int quiet=0,retval,ins_result;
    int total_eventset=PAPI_NULL,miss_eventset=PAPI_NULL;

    quiet=tests_quiet(argc,argv);

    if (!quiet) {
        printf("\nTesting the PAPI_BR_PRC event.\n\n");
        printf("This should measure predicted correctly conditional branches\n");
        printf("If such a counter is not available, it may report predicted correctly\n");
        printf("total branches instead.\n");
    }

    /* Init the PAPI library */
    retval = PAPI_library_init( PAPI_VER_CURRENT );
    if ( retval != PAPI_VER_CURRENT ) {
        test_fail( __FILE__, __LINE__, "PAPI_library_init", retval );
    }

    /* Create total eventset */
    retval=PAPI_create_eventset(&total_eventset);
    if (retval!=PAPI_OK) {
        test_fail( __FILE__, __LINE__, "PAPI_create_eventset", retval );
    }

    retval=PAPI_add_named_event(total_eventset,"PAPI_BR_CN");
    if (retval!=PAPI_OK) {
        if (!quiet) printf("Could not add PAPI_BR_CN\n");
        //test_skip( __FILE__, __LINE__, "adding PAPI_BR_CN", retval );

        retval=PAPI_add_named_event(total_eventset,"PAPI_BR_INS");
        if (retval!=PAPI_OK) {
            if (!quiet) printf("Could not add PAPI_BR_INS\n");
            test_skip( __FILE__, __LINE__, "adding PAPI_BR_INS", retval );
        }
    }





    /* Create correct eventset */
    retval=PAPI_create_eventset(&miss_eventset);
    if (retval!=PAPI_OK) {
        test_fail( __FILE__, __LINE__, "PAPI_create_eventset", retval );
    }

    retval=PAPI_add_named_event(miss_eventset,"PAPI_BR_PRC");
    if (retval!=PAPI_OK) {
        if (!quiet) printf("Could not add PAPI_BR_PRC\n");
        test_skip( __FILE__, __LINE__, "adding PAPI_BR_PRC", retval );
    }

    if (!quiet) {
        printf("\nPart 1: Testing that easy to predict loop has few misses\n");
        printf("Testing a loop with %lld branches (%d times):\n",
            expected,num_runs);
        printf("\tOn a simple loop like this, "
            "hit rate should be very high.\n");
    }

    for(i=0;i<num_runs;i++) {

        PAPI_reset(miss_eventset);
                PAPI_start(miss_eventset);

        ins_result=branches_testcode();

        retval=PAPI_stop(miss_eventset,&count);

        if (ins_result==CODE_UNIMPLEMENTED) {
            fprintf(stderr,"\tCode unimplemented\n");
            test_skip( __FILE__, __LINE__, "unimplemented", 0);
        }

        if (retval!=PAPI_OK) {
            test_fail( __FILE__, __LINE__,
                "reading PAPI_TOT_INS", retval );
        }

        if (count>high) high=count;
        if ((low==0) || (count<low)) low=count;
        total+=count;
    }

    average=(total/num_runs);

    if (!quiet) printf("\tAverage number of branch hits: %lld\n",average);

    if (average<expected/2) {
        if (!quiet) printf("Branch miss rate too high\n");
        test_fail( __FILE__, __LINE__, "Error too high", 1 );
    }

    /*******************/

    if (!quiet) {
        printf("\nPart 2\n");
    }

    high=0; low=0; total=0;

    for(i=0;i<num_runs;i++) {
        PAPI_reset(total_eventset);
                PAPI_start(total_eventset);

        ins_result=random_branches_testcode(num_random_branches,1);

        retval=PAPI_stop(total_eventset,&count);

        if (ins_result==CODE_UNIMPLEMENTED) {
            fprintf(stderr,"\tCode unimplemented\n");
            test_skip( __FILE__, __LINE__, "unimplemented", 0);
        }

        if (retval!=PAPI_OK) {
            test_fail( __FILE__, __LINE__,
                "reading PAPI_TOT_INS", retval );
        }

        if (count>high) high=count;
        if ((low==0) || (count<low)) low=count;
        total+=count;
    }

    average=total/num_runs;

    expected=average;
    if (!quiet) {
        printf("\nTesting a function that branches "
            "based on a random number\n");
        printf("   The loop has %lld conditional branches.\n",expected);
        printf("   %d are random branches.\n",num_random_branches);
    }

    high=0; low=0; total=0;

    for(i=0;i<num_runs;i++) {
        PAPI_reset(miss_eventset);
                PAPI_start(miss_eventset);

        ins_result=random_branches_testcode(num_random_branches,1);

        retval=PAPI_stop(miss_eventset,&count);

        if (ins_result==CODE_UNIMPLEMENTED) {
            fprintf(stderr,"\tCode unimplemented\n");
            test_skip( __FILE__, __LINE__, "unimplemented", 0);
        }

        if (retval!=PAPI_OK) {
            test_fail( __FILE__, __LINE__,
                "reading eventset", retval );
        }

        if (count>high) high=count;
        if ((low==0) || (count<low)) low=count;
        total+=count;
    }

    average=total/num_runs;

    expected_low=expected-((num_random_branches/4)*3);
    expected_high=expected-(num_random_branches/4);

    if (!quiet) {
        printf("\nOut of %lld branches, "
            "%lld were correctly predicted\n",expected,average);
        printf("Assuming a good random number generator and no "
            "freaky luck\n");
        printf("The mispredicts should be roughly "
            "between %lld and %lld\n",
            expected_low,expected_high);

    }

    if ( average < expected_low) {
        if (!quiet) printf("Branch hits too low\n");
        test_fail( __FILE__, __LINE__, "Error too low", 1 );
    }

    if (average > expected_high) {
        if (!quiet) printf("Branch hits too high\n");
        test_fail( __FILE__, __LINE__, "Error too high", 1 );
    }

    if (!quiet) printf("\n");

    test_pass( __FILE__ );

    PAPI_shutdown();

    return 0;

}