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//================================================================= // // rand3.c // // Testcase for C library rand() // //================================================================= //####ECOSGPLCOPYRIGHTBEGIN#### // ------------------------------------------- // This file is part of eCos, the Embedded Configurable Operating System. // Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc. // // eCos is free software; you can redistribute it and/or modify it under // the terms of the GNU General Public License as published by the Free // Software Foundation; either version 2 or (at your option) any later version. // // eCos is distributed in the hope that it will be useful, but WITHOUT ANY // WARRANTY; without even the implied warranty of MERCHANTABILITY or // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License // for more details. // // You should have received a copy of the GNU General Public License along // with eCos; if not, write to the Free Software Foundation, Inc., // 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. // // As a special exception, if other files instantiate templates or use macros // or inline functions from this file, or you compile this file and link it // with other works to produce a work based on this file, this file does not // by itself cause the resulting work to be covered by the GNU General Public // License. However the source code for this file must still be made available // in accordance with section (3) of the GNU General Public License. // // This exception does not invalidate any other reasons why a work based on // this file might be covered by the GNU General Public License. // // Alternative licenses for eCos may be arranged by contacting Red Hat, Inc. // at http://sources.redhat.com/ecos/ecos-license/ // ------------------------------------------- //####ECOSGPLCOPYRIGHTEND#### //================================================================= //#####DESCRIPTIONBEGIN#### // // Author(s): jlarmour // Contributors: // Date: 2000-04-30 // Description: Contains testcode for C library rand() function. This tests // that random numbers are distributed well between 0 and // RAND_MAX // // //####DESCRIPTIONEND#### // INCLUDES #include <stdlib.h> #include <cyg/infra/testcase.h> // CONSTANTS #define NUM_BUCKETS 1000 // how many categories to define #define TEST_LENGTH 200000 // how many samples to take - careful // when reducing this since it also reduces // BUCKET_DIFF_TOLERANCE below. If you reduce // it too low, BUCKET_DIFF_TOLERANCE will need // a fudge factor #define BUCKET_SIZE (RAND_MAX / NUM_BUCKETS) // number space allocated // to bucket from 0..RAND_MAX #define NUM_PER_BUCKET (TEST_LENGTH/NUM_BUCKETS) // Expected number that went // into each bucket at end // how much the buckets can vary at the end. #define BUCKET_DIFF_TOLERANCE (NUM_PER_BUCKET/4) // allowed to vary 25% // FUNCTIONS static __inline__ int my_abs(int i) { return (i < 0) ? -i : i; } // my_abs() int main(int argc, char *argv[]) { // divide the space from 0..RAND_MAX into NUM_BUCKETS categories *BUT* // RAND_MAX / NUM_BUCKETS may not divide exactly so we leave space for // the bits left over, in case there are any! So we add 1. static cyg_uint8 rand_bucket[NUM_BUCKETS+1]; cyg_ucount32 count; // loop variable int r; // temp for rand() variable 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"); for ( count=0; count < TEST_LENGTH; ++count ) { r = rand(); ++rand_bucket[ r / BUCKET_SIZE ]; if ((count%10000)==0) CYG_TEST_STILL_ALIVE(count, "Still testing..."); } // for for ( count=0; count < NUM_BUCKETS; ++count ) { cyg_ucount32 diff; diff = my_abs( rand_bucket[count] - NUM_PER_BUCKET ); if ( diff > BUCKET_DIFF_TOLERANCE ) break; } // for // if the previous loop completed, we may want to check the "extra" // bucket (see the comment at the top) that may have some bits in if // RAND_MAX doesn't split into NUM_BUCKETS evenly. The number of random // digits that fell into that bucket would be expected to be proportional // to the ratio of the remainder of (RAND_MAX % NUM_BUCKETS) to // NUM_BUCKETS. if (count == NUM_BUCKETS) { cyg_ucount32 rem; cyg_ucount32 last_bucket_expected; cyg_ucount32 diff; rem = RAND_MAX % NUM_BUCKETS; last_bucket_expected = (rem * NUM_PER_BUCKET) / BUCKET_SIZE; diff = my_abs(last_bucket_expected - rand_bucket[count]); CYG_TEST_PASS_FAIL(diff <= BUCKET_DIFF_TOLERANCE, "Upper bound fencepost test"); } CYG_TEST_PASS_FAIL( (count >= NUM_BUCKETS), "even distribution of rand()"); CYG_TEST_FINISH("Finished tests from testcase " __FILE__ " for " "C library rand() function"); } // main() // EOF rand3.c