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220 lines
6.5 KiB
220 lines
6.5 KiB
/************************************************************ |
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* lib/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 <spudmonkey@racsa.co.cr> |
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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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* Compilation Switches |
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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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* Definitions |
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************************************************************/ |
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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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/* 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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#if CONFIG_LIB_RAND_ORDER == 1 |
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# define RND_CONSTP RND1_CONSTP |
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#elif CONFIG_LIB_RAND_ORDER == 2 |
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# define RND_CONSTP RND2_CONSTP |
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#else |
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# define RND_CONSTP RND3_CONSTP |
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#endif |
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/************************************************************ |
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* Private Type Declarations |
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************************************************************/ |
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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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static double_t frand1(void); |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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static double_t frand2(void); |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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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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* Global Constant Data |
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**********************************************************/ |
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/************************************************************ |
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* Global Variables |
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************************************************************/ |
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/********************************************************** |
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* Private Constant Data |
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**********************************************************/ |
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/************************************************************ |
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* Private Variables |
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************************************************************/ |
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static unsigned long g_nRandInt1; |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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static unsigned long g_nRandInt2; |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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static unsigned long g_nRandInt3; |
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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 nResult; |
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double_t fRatio; |
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/* Loop to be sure a legal random number is generated */ |
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do { |
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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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fRatio = frand1(); |
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#elif (CONFIG_LIB_RAND_ORDER == 2) |
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fRatio = frand2(); |
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#else |
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fRatio = frand3(); |
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#endif |
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/* Then, produce the return-able value */ |
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nResult = (unsigned long)(((double_t)nLimit) * fRatio); |
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} while (nResult >= (unsigned long)nLimit); |
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return (unsigned int)nResult; |
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} /* end nrand */ |
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static double_t frand1(void) |
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{ |
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unsigned long nRandInt; |
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/* First order congruential generator */ |
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nRandInt = (RND1_CONSTK * g_nRandInt1) % RND1_CONSTP; |
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g_nRandInt1 = nRandInt; |
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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)nRandInt) / ((double_t)RND_CONSTP); |
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} /* end frand */ |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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static double_t frand2(void) |
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{ |
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unsigned long nRandInt; |
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/* Second order congruential generator */ |
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nRandInt = (RND2_CONSTK1 * g_nRandInt1 + RND2_CONSTK2 * g_nRandInt2) % |
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RND2_CONSTP; |
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g_nRandInt2 = g_nRandInt1; |
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g_nRandInt1 = nRandInt; |
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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)nRandInt) / ((double_t)RND_CONSTP); |
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} /* end frand */ |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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static double_t frand3(void) |
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{ |
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unsigned long nRandInt; |
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/* Third order congruential generator */ |
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nRandInt = (RND3_CONSTK1 * g_nRandInt1 + RND3_CONSTK2 * g_nRandInt2 + |
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RND3_CONSTK2 * g_nRandInt3) % RND3_CONSTP; |
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g_nRandInt3 = g_nRandInt2; |
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g_nRandInt2 = g_nRandInt1; |
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g_nRandInt1 = nRandInt; |
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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)nRandInt) / ((double_t)RND_CONSTP); |
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} /* end frand */ |
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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_nRandInt1 = seed; |
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#if (CONFIG_LIB_RAND_ORDER > 1) |
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g_nRandInt2 = seed; |
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(void)frand1(); |
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#if (CONFIG_LIB_RAND_ORDER > 2) |
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g_nRandInt3 = seed; |
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(void)frand2(); |
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#endif |
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#endif |
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} /* end srand */ |
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int rand(void) |
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{ |
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return (int)nrand(32768); |
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} /* end rand */ |
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