rand4.c

ecos为实时嵌入式操作系统

//=================================================================
//
//        rand4.c
//
//        Testcase for C library rand()
//
//=================================================================
//####COPYRIGHTBEGIN####
//
// -------------------------------------------
// The contents of this file are subject to the Cygnus eCos Public License
// Version 1.0 (the "License"); you may not use this file except in
// compliance with the License.  You may obtain a copy of the License at
// http://sourceware.cygnus.com/ecos
// 
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the
// License for the specific language governing rights and limitations under
// the License.
// 
// The Original Code is eCos - Embedded Cygnus Operating System, released
// September 30, 1998.
// 
// The Initial Developer of the Original Code is Cygnus.  Portions created
// by Cygnus are Copyright (C) 1998,1999 Cygnus Solutions.  All Rights Reserved.
// -------------------------------------------
//
//####COPYRIGHTEND####
//=================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):     rosalia
// Contributors:  rosalia, jlarmour
// Date:          1999-03-19
// 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.h>          // C library configuration

// INCLUDES

#include <stdlib.h>
#include <cyg/infra/testcase.h>
#include <sys/cstartup.h>          // C library initialisation

// CONSTANTS

#define TEST_LENGTH 100000        // how many samples to take

// DEFINES

#define TEST_VALID (!defined(CYGIMP_LIBC_RAND_SIMPLEST))

// FUNCTIONS


externC void
cyg_package_start( void )
{
    cyg_iso_c_start();
} // cyg_package_start()

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
    
    // FIXME: 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