suite/tests/common/fib.c

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

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/* undefine this for a performance test */
#ifndef NIGHTLY_REGRESSION
# define NIGHTLY_REGRESSION
#endif

#include "tools.h"

#include <stdio.h>

#ifdef WINDOWS
/* and compile with user32.lib */
#include <windows.h>
#endif

#ifdef NIGHTLY_REGRESSION
#  define ITER 10*1000
#else
#  define ITER 10*200*1000 // *100
#endif

#define GOAL 32 /* recursive fib of course is exponential here */

/* now stay a little more realistic depths that fit in the RSB */
#define DEPTH 12

/* ignore overflow errors */
int
fib(int n) {
    if (n <= 1) return 1;
    /* for drcov test, we add a line that won't be executed */
    if (n > 100)
        return 0;
    return fib(n-1) + fib(n-2);
}

int
main(int argc, char** argv)
{
    int i, t;

    INIT();
    USE_USER32();

    print("fib(%d)=%d\n", 5, fib(5));
    print("fib(%d)=%d\n", 15, fib(15));
    /* deep recursion */
    print("fib(%d)=%d\n", 25, fib(25));

    /* show recursion */
    for (i=0; i<=GOAL; i++) {
        t = fib(i);
        print("fib(%d)=%d\n", i, t);
    }

    for (i=0; i<=ITER; i++) {
        t = fib(DEPTH);
    }

    print("fib(%d)=%d\n", DEPTH, t);
}

/*
It is amazing that with default options native=13s dr=12s

only when optimized differences show up in the other direction
$ cl /O2 -I.. fib.c
native=8s dr=11s   ITER=? DEPTH=?

$ cl /O2  /Zi fib.c -I.. /link /incremental:no user32.lib
*/