b08a86171f
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3 42af7a65-404d-4744-a932-0658087f49c3
213 lines
6.0 KiB
C
213 lines
6.0 KiB
C
/************************************************************
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* lib_rand.c
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*
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* Copyright (C) 2007 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 Gregory Nutt 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 RND_ORDER
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#define RND_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 RND_ORDER == 1
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# define RND_CONSTP RND1_CONSTP
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#elif RND_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 frand1(void);
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#if (RND_ORDER > 1)
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static double frand2(void);
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#if (RND_ORDER > 2)
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static double 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 (RND_ORDER > 1)
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static unsigned long g_nRandInt2;
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#if (RND_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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* 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 (RND_ORDER > 1)
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g_nRandInt2 = seed;
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(void)frand1();
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#if (RND_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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static unsigned int nrand(unsigned int nLimit)
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{
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unsigned long nResult;
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double 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 (RND_ORDER == 1)
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fRatio = frand1();
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#elif (RND_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)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 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)nRandInt) / ((double)RND_CONSTP);
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} /* end frand */
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#if (RND_ORDER > 1)
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static double 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)nRandInt) / ((double)RND_CONSTP);
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} /* end frand */
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#if (RND_ORDER > 2)
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static double frand(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)nRandInt) / ((double)RND_CONSTP);
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} /* end frand */
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#endif
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#endif
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