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277 lines
7.6 KiB
277 lines
7.6 KiB
/**************************************************************************** |
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* libc/stdlib/lib_rand.c |
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* |
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* Copyright (C) 2007, 2011 Gregory Nutt. All rights reserved. |
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* Author: Gregory Nutt <gnutt@nuttx.org> |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* 3. Neither the name NuttX nor the names of its contributors may be |
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* used to endorse or promote products derived from this software |
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* without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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* POSSIBILITY OF SUCH DAMAGE. |
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* |
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****************************************************************************/ |
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/**************************************************************************** |
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* Included Files |
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****************************************************************************/ |
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#include <sys/types.h> |
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#include <stdlib.h> |
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/**************************************************************************** |
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* Pre-processor Definitions |
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****************************************************************************/ |
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/* First, second, and thired order congruential generators are supported */ |
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#ifndef CONFIG_LIB_RAND_ORDER |
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# define CONFIG_LIB_RAND_ORDER 1 |
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#endif |
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#if CONFIG_LIB_RAND_ORDER > 3 |
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# undef CONFIG_LIB_RAND_ORDER |
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# define CONFIG_LIB_RAND_ORDER 3 |
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#endif |
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/* Values needed by the random number generator */ |
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#define RND1_CONSTK 470001 |
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#define RND1_CONSTP 999563 |
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#define RND2_CONSTK1 366528 |
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#define RND2_CONSTK2 508531 |
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#define RND2_CONSTP 998917 |
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#define RND3_CONSTK1 360137 |
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#define RND3_CONSTK2 519815 |
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#define RND3_CONSTK3 616087 |
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#define RND3_CONSTP 997783 |
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/**************************************************************************** |
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* Private Function Prototypes |
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****************************************************************************/ |
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static unsigned int nrand(unsigned int nLimit); |
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/* First order congruential generators */ |
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static inline unsigned long fgenerate1(void); |
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#if (CONFIG_LIB_RAND_ORDER == 1) |
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static double_t frand1(void); |
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#endif |
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/* Second order congruential generators */ |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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static inline unsigned long fgenerate2(void); |
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#if (CONFIG_LIB_RAND_ORDER == 2) |
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static double_t frand2(void); |
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#endif |
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/* Third order congruential generators */ |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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static inline unsigned long fgenerate3(void); |
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static double_t frand3(void); |
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#endif |
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#endif |
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/**************************************************************************** |
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* Private Data |
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****************************************************************************/ |
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static unsigned long g_randint1; |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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static unsigned long g_randint2; |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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static unsigned long g_randint3; |
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#endif |
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#endif |
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/**************************************************************************** |
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* Private Functions |
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****************************************************************************/ |
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static unsigned int nrand(unsigned int nLimit) |
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{ |
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unsigned long result; |
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double_t ratio; |
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/* Loop to be sure a legal random number is generated */ |
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do |
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{ |
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/* Get a random integer in the requested range */ |
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#if (CONFIG_LIB_RAND_ORDER == 1) |
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ratio = frand1(); |
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#elif (CONFIG_LIB_RAND_ORDER == 2) |
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ratio = frand2(); |
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#else /* if (CONFIG_LIB_RAND_ORDER > 2) */ |
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ratio = frand3(); |
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#endif |
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/* Then, produce the return-able value */ |
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result = (unsigned long)(((double_t)nLimit) * ratio); |
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} |
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while (result >= (unsigned long)nLimit); |
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return (unsigned int)result; |
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} |
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/* First order congruential generators */ |
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static inline unsigned long fgenerate1(void) |
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{ |
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unsigned long randint; |
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/* First order congruential generator. One may be added to the result of the |
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* generated value to avoid the value zero. This would be fatal for the |
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* first order random number generator. |
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*/ |
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randint = (RND1_CONSTK * g_randint1) % RND1_CONSTP; |
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g_randint1 = (randint == 0 ? 1 : randint); |
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return randint; |
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} |
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#if (CONFIG_LIB_RAND_ORDER == 1) |
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static double_t frand1(void) |
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{ |
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/* First order congruential generator. */ |
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unsigned long randint = fgenerate1(); |
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/* Construct an floating point value in the range from 0.0 up to 1.0 */ |
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return ((double_t)randint) / ((double_t)RND1_CONSTP); |
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} |
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#endif |
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/* Second order congruential generators */ |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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static inline unsigned long fgenerate2(void) |
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{ |
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unsigned long randint; |
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/* Second order congruential generator. */ |
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randint = (RND2_CONSTK1 * g_randint1 + |
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RND2_CONSTK2 * g_randint2) % RND2_CONSTP; |
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g_randint2 = g_randint1; |
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g_randint1 = randint; |
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/* We cannot permit both values to become zero. That would be fatal for the |
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* second order random number generator. |
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*/ |
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if (g_randint2 == 0 && g_randint1 == 0) |
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{ |
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g_randint2 = 1; |
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} |
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return randint; |
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} |
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#if (CONFIG_LIB_RAND_ORDER == 2) |
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static double_t frand2(void) |
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{ |
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/* Second order congruential generator */ |
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unsigned long randint = fgenerate2(); |
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/* Construct an floating point value in the range from 0.0 up to 1.0 */ |
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return ((double_t)randint) / ((double_t)RND2_CONSTP); |
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} |
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#endif |
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/* Third order congruential generators */ |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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static inline unsigned long fgenerate3(void) |
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{ |
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unsigned long randint; |
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/* Third order congruential generator. */ |
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randint = (RND3_CONSTK1 * g_randint1 + |
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RND3_CONSTK2 * g_randint2 + |
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RND3_CONSTK2 * g_randint3) % RND3_CONSTP; |
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g_randint3 = g_randint2; |
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g_randint2 = g_randint1; |
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g_randint1 = randint; |
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/* We cannot permit all three values to become zero. That would be fatal for the |
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* third order random number generator. |
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*/ |
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if (g_randint3 == 0 && g_randint2 == 0 && g_randint1 == 0) |
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{ |
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g_randint3 = 1; |
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} |
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return randint; |
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} |
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static double_t frand3(void) |
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{ |
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/* Third order congruential generator */ |
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unsigned long randint = fgenerate3(); |
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/* Construct an floating point value in the range from 0.0 up to 1.0 */ |
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return ((double_t)randint) / ((double_t)RND3_CONSTP); |
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} |
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#endif |
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#endif |
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/**************************************************************************** |
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* Public Functions |
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****************************************************************************/ |
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/**************************************************************************** |
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* Function: srand, rand |
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****************************************************************************/ |
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void srand(unsigned int seed) |
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{ |
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g_randint1 = seed; |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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g_randint2 = seed; |
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(void)fgenerate1(); |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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g_randint3 = seed; |
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(void)fgenerate2(); |
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#endif |
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#endif |
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} |
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int rand(void) |
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{ |
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return (int)nrand(32768); |
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}
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