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//----------------------------------------------------------------------------------------------------
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//$Header: /home/dashley/cvsrep/e3ft_gpl01/e3ft_gpl01/dtaipubs/cron/2010/blackjack_201010/source/bjcceval/random.c,v 1.7 2012/04/15 12:57:08 dashley Exp $
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//----------------------------------------------------------------------------------------------------
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//Copyright (C) 2012, David T. Ashley.
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//
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//This file is part of BJCCEVAL, a program that evaluates by simulation
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//the best basic strategy, card-counting, and other playing strategies
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//for several variants of the game of Blackjack.
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//
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//BJCCEVAL is free software: you can redistribute it and/or modify
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//it under the terms of the GNU General Public License as published by
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//the Free Software Foundation, either version 3 of the License, or
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//(at your option) any later version.
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//
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//BJCCEVAL is distributed in the hope that it will be useful,
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//but WITHOUT ANY WARRANTY; without even the implied warranty of
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//MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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//GNU General Public License for more details.
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//
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//You should have received a copy of the GNU General Public License
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//along with this program. If not, see <http://www.gnu.org/licenses/>.
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//(A copy of the GNU General Public License, Version 3 is provided in
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//the file "COPYING" distributed with BJCCEVAL.)
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//
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//David T. Ashley can be contacted at DASHLEY@GMAIL.COM and/or at
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//P.O. Box 918, Marshall MI 49068.
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//----------------------------------------------------------------------------------------------------
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#define MODULE_RANDOM
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#include "mt19937.h"
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#include "random.h"
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//Returns a single random bit as FALSE or TRUE.
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//
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//Unit-tested 20120411. Unit-testing involved stepping
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//through the function and observing behavior.
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//
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unsigned RANDOM_Bit(void)
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{
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static unsigned nbitsavail = 0;
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static unsigned bit_buffer;
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unsigned rv;
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if (! nbitsavail)
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{
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bit_buffer = RANDOM_Uint32();
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nbitsavail = 32;
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}
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if (bit_buffer & 0x01)
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{
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rv = 1;
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}
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else
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{
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rv = 0;
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}
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bit_buffer >>= 1;
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nbitsavail--;
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return(rv);
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}
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//Returns a random unsigned integer. Because the MT19937
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//test vectors passed when the MT19937 code was added,
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//this was not carefully unit-tested.
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//
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//However, a basic unit test involving 256 bins for modulo
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//result and 256 bins for partition was performed. The results
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//seemed reasonable.
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//
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//Unit tested 20120411.
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//
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unsigned RANDOM_Uint32(void)
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{
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unsigned rv;
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rv = MT19937_genrand_int32();
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return(rv);
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}
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//Returns a randomly-distributed value between min and max inclusive.
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//
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//20120411: Unit-tested. Attempted full statement coverage.
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//
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unsigned RANDOM_UintBounded32(unsigned min, unsigned max)
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{
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unsigned diff;
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//Difference between max and min values.
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unsigned span;
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//Number of different values that could be returned that would satisfy the
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//criteria of being between min and max, inclusive.
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unsigned max_random_allowed;
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//Max random value that would be of use to us.
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unsigned random_val;
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//The random value obtained.
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unsigned rv;
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//The value returned to the caller.
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//Swap min and max if they are reversed.
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if (min > max)
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{
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unsigned temp;
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temp = min;
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min = max;
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max = temp;
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}
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//Calculate parameters that parameterize the generation.
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diff = max - min;
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span = diff + 1; //Possible rollover to 0, but this case excluded below.
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if (diff == 0)
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{
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rv = min; //We can choose only one value. Choose it.
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}
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else if (diff == 0xFFFFFFFF)
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{
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rv = RANDOM_Uint32(); //The input parameters are 0 and 0xFFFFFFFF. We can't
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//safely calculate with this max range, so return without
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//further calculation.
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}
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else
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{
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//At this point we can possibly "fold" or "equivalence class"
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//any random integer we obtain to meet the interval.
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//
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//Figure out how big of a random unsigned integer would be useful to us.
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//
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//The correct expression for the maximum random integer that is useful to us is
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//
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// 0x100000000 - (0x100000000 mod span) - 1.
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//
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//This isn't easy to calculate with 32-bit arithmetic.
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//
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// 0xFFFFFFFF - (0x100000000 mod span)
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//
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//Note that
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//
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// (0x100000000 mod span) = ((0xFFFFFFFF mod span) + 1) mod span
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//
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//So the overall expression is:
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//
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// 0xFFFFFFFF - (((0xFFFFFFFF mod span) + 1) mod span)
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//
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max_random_allowed = 0xFFFFFFFF - (((0xFFFFFFFF % span) + 1) % span);
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do
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{
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random_val = RANDOM_Uint32();
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} while (random_val > max_random_allowed);
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rv = (random_val % span) + min;
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}
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return(rv);
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}
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//Returns a uniformly distributed signed integer.
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//
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//20120414: Unit tested to be sure it attains test cases commented out below.
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//
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int RANDOM_Int32(void)
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{
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unsigned ov;
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int rv;
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//Because the distribution of an unsigned is uniform (no previous
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//value gives information about the next value) it should be
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//acceptable just to let an unsigned int be remapped as an int.
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ov = RANDOM_Uint32();
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rv = ov - 0x80000000;
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//Debugging trap to be sure values map correctly from unsigned to signed.
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//
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//if ( (ov == 0x00000000) || (ov == 0x00000001) || (ov == 0x7FFFFFFF) || (ov == 0x80000000)
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// || (ov == 0x80000001) || (ov == 0xFFFFFFFE) || (ov == 0xFFFFFFFF))
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// {
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// static unsigned count=0;
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//
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// count++;
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//
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// printf("----------\n");
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// printf("Result #%u\n", count);
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// printf("ov: %u rv: %d\n", ov, rv);
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// printf("ov: %08X rv: %08X\n", ov, rv);
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// }
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return(rv);
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}
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//Returns a random signed integer in the interval [min, max].
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//
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//20120415: Several intervals checked. Function seems OK, including intervals
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//at negative and positive limits.
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//
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int RANDOM_IntBounded32(int min, int max)
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{
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long long bigmin, bigmax, bigdiff;
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long long int ri;
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if (min > max)
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{
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int temp;
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temp = min;
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min = max;
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max = temp;
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}
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bigmin = min;
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bigmax = max;
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bigdiff = bigmax - bigmin;
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ri = RANDOM_UintBounded32(0, (unsigned)bigdiff);
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ri += bigmin;
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return((int)ri);
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}
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//Returns version control information for the .C file.
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//
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const char *RANDOM_Vcinfo_C(void)
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{
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return("$Revision: 1.7 $");
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}
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//Returns version control for the .H file.
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//
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const char *RANDOM_Vcinfo_H(void)
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{
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return(RANDOM_VCINFO_H);
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}
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#if defined(P_TEST) || defined(P_TEST_RANDOM)
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int RANDOM_Test(void)
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{
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return(1);
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}
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#endif
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//----------------------------------------------------------------------------------------------------
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//$Log: random.c,v $
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//Revision 1.7 2012/04/15 12:57:08 dashley
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//Unit testing performed.
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//
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//Revision 1.6 2012/04/12 01:51:57 dashley
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//Edits.
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//
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//Revision 1.5 2012/04/11 03:31:51 dashley
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//Edits.
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//
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//Revision 1.4 2012/03/30 00:20:14 dashley
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//Edits.
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//
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//Revision 1.3 2012/03/29 23:44:01 dashley
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//Edits.
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//
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//Revision 1.2 2012/03/15 23:38:08 dashley
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//License text enhanced.
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//
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//Revision 1.1 2012/03/11 21:01:46 dashley
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//Initial checkin.
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//----------------------------------------------------------------------------------------------------
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//End of $RCSfile: random.c,v $
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//----------------------------------------------------------------------------------------------------
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