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//=================================================================

//

//        rand4.c

//

//        Testcase for C library rand()

//

//=================================================================

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//=================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):     rosalia

// Contributors:  jlarmour

// Date:          2000-04-30

// Description:   Contains testcode for C library rand() function. This tests

//                that random numbers do not have periodicity in the lower

//                bit

//

//

//####DESCRIPTIONEND####

// CONFIGURATION

#include <pkgconf/libc_stdlib.h>   // Configuration header

// INCLUDES

#include <stdlib.h>

#include <cyg/infra/testcase.h>

// CONSTANTS

#define TEST_LENGTH 100000        // how many samples to take

// DEFINES

#define TEST_VALID (!defined(CYGIMP_LIBC_RAND_SIMPLEST))

// FUNCTIONS

int

main(int argc, char *argv[])

{

#if TEST_VALID

    int i;

    int r, prev, prevprev;

    int how_many_periodics = 0;

#endif

    CYG_TEST_INIT();

    CYG_TEST_INFO("Starting tests from testcase " __FILE__ " for C library "

                  "rand() function");

    CYG_TEST_INFO("This test tests the distribution of random numbers and");

    CYG_TEST_INFO("may take some time");

#if TEST_VALID

    r = rand() % 2;

    prev = r;

    r = rand() % 2;

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

      prevprev = prev;

      prev = r;

      r = rand() % 2;

      if (r == prevprev) {

        ++how_many_periodics;

      }

      if (how_many_periodics > (2*TEST_LENGTH)/3) {

        break;

      }

    }

    CYG_TEST_PASS_FAIL( (how_many_periodics <= (2*TEST_LENGTH)/3),

                        "periodicity of rand() in lowest bit");

#else

    // TODO: should be an _expected_ fail i.e. XFAIL

    CYG_TEST_NA("Chosen rand algorithm is known to fail this test");

#endif

    CYG_TEST_FINISH("Finished tests from testcase " __FILE__ " for "

                    "C library rand() function");

} // main()

// EOF rand4.c