kopia lustrzana https://github.com/OpenRTX/OpenRTX
271 wiersze
11 KiB
C
271 wiersze
11 KiB
C
/*
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*********************************************************************************************************
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* uC/LIB
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* Custom Library Modules
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*
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* Copyright 2004-2020 Silicon Laboratories Inc. www.silabs.com
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*
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* SPDX-License-Identifier: APACHE-2.0
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*
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* This software is subject to an open source license and is distributed by
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* Silicon Laboratories Inc. pursuant to the terms of the Apache License,
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* Version 2.0 available at www.apache.org/licenses/LICENSE-2.0.
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*
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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*
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* MATHEMATIC OPERATIONS
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*
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* Filename : lib_math.c
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* Version : V1.39.00
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*********************************************************************************************************
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* Note(s) : (1) NO compiler-supplied standard library functions are used in library or product software.
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*
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* (a) ALL standard library functions are implemented in the custom library modules :
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*
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* (1) \<Custom Library Directory>\lib_*.*
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*
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* (2) \<Custom Library Directory>\Ports\<cpu>\<compiler>\lib*_a.*
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*
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* where
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* <Custom Library Directory> directory path for custom library software
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* <cpu> directory name for specific processor (CPU)
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* <compiler> directory name for specific compiler
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*
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* (b) Product-specific library functions are implemented in individual products.
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*
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*********************************************************************************************************
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* Notice(s) : (1) The Institute of Electrical and Electronics Engineers and The Open Group, have given
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* us permission to reprint portions of their documentation. Portions of this text are
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* reprinted and reproduced in electronic form from the IEEE Std 1003.1, 2004 Edition,
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* Standard for Information Technology -- Portable Operating System Interface (POSIX),
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* The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute
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* of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
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* discrepancy between these versions and the original IEEE and The Open Group Standard,
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* the original IEEE and The Open Group Standard is the referee document. The original
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* Standard can be obtained online at http://www.opengroup.org/unix/online.html.
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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* INCLUDE FILES
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*********************************************************************************************************
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*/
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#define MICRIUM_SOURCE
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#define LIB_MATH_MODULE
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#include <lib_math.h>
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/*
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*********************************************************************************************************
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* LOCAL DEFINES
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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* LOCAL CONSTANTS
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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* LOCAL DATA TYPES
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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* LOCAL TABLES
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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* LOCAL GLOBAL VARIABLES
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*********************************************************************************************************
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*/
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RAND_NBR Math_RandSeedCur; /* Cur rand nbr seed. */
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/*
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*********************************************************************************************************
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* LOCAL FUNCTION PROTOTYPES
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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* LOCAL CONFIGURATION ERRORS
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*********************************************************************************************************
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*/
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/*
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*********************************************************************************************************
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* Math_Init()
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*
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* Description : (1) Initialize Mathematic Module :
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*
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* (a) Initialize random number seed value
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*
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*
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* Argument(s) : none.
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*
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* Return(s) : none.
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*
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* Caller(s) : Application.
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*
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* Note(s) : (2) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "if rand()
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* is called before any calls to srand() are made, the same sequence shall be generated
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* as when srand() is first called with a seed value of 1".
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*********************************************************************************************************
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*/
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void Math_Init (void)
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{
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Math_RandSetSeed((RAND_NBR)RAND_SEED_INIT_VAL); /* See Note #2. */
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}
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/*
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*********************************************************************************************************
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* Math_RandSetSeed()
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*
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* Description : Set the current pseudo-random number generator seed.
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*
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* Argument(s) : seed Initial (or current) value to set for the pseudo-random number sequence.
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*
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* Return(s) : none.
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*
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* Caller(s) : Application.
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*
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* Note(s) : (1) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "srand()
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* ... uses the argument as a seed for a new sequence of pseudo-random numbers to be
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* returned by subsequent calls to rand()".
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*
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* (2) 'Math_RandSeedCur' MUST always be accessed exclusively in critical sections.
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*
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* See also 'Math_Rand() Note #1b'.
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*********************************************************************************************************
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*/
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void Math_RandSetSeed (RAND_NBR seed)
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{
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CPU_SR_ALLOC();
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CPU_CRITICAL_ENTER();
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Math_RandSeedCur = seed;
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CPU_CRITICAL_EXIT();
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}
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/*
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*********************************************************************************************************
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* Math_Rand()
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*
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* Description : Calculate the next pseudo-random number.
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*
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* Argument(s) : none.
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*
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* Return(s) : Next pseudo-random number in the sequence after 'Math_RandSeedCur'.
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*
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* Caller(s) : Application.
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*
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* Note(s) : (1) (a) The pseudo-random number generator is implemented as a Linear Congruential
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* Generator (LCG).
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*
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* (b) The pseudo-random number generated is in the range [0, RAND_LCG_PARAM_M].
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*
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* See also 'Math_RandSeed() Note #1'.
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*
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* (2) (a) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "rand()
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* ... need not be reentrant ... [and] is not required to be thread-safe".
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*
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* (b) However, in order to implement Math_Rand() as re-entrant; 'Math_RandSeedCur' MUST
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* always be accessed & updated exclusively in critical sections.
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*
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* See also 'Math_RandSeed() Note #2'.
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*********************************************************************************************************
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*/
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RAND_NBR Math_Rand (void)
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{
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RAND_NBR seed;
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RAND_NBR rand_nbr;
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CPU_SR_ALLOC();
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CPU_CRITICAL_ENTER();
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seed = Math_RandSeedCur;
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rand_nbr = Math_RandSeed(seed);
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Math_RandSeedCur = rand_nbr;
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CPU_CRITICAL_EXIT();
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return (rand_nbr);
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}
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/*
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*********************************************************************************************************
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* Math_RandSeed()
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*
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* Description : Calculate the next pseudo-random number.
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*
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* Argument(s) : seed Initial (or current) value for the pseudo-random number sequence.
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*
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* Return(s) : Next pseudo-random number in the sequence after 'seed'.
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*
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* Caller(s) : Math_Rand(),
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* Application.
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*
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* Note(s) : (1) (a) BSD/ANSI-C implements rand() as a Linear Congruential Generator (LCG) :
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*
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* (A) random_number = [(a * random_number ) + b] modulo m
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* n + 1 n
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*
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* where
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* (1) (a) random_number Next random number to generate
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* n+1
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* (b) random_number Previous random number generated
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* n
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*
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* (2) a = RAND_LCG_PARAM_A LCG multiplier
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* (3) b = RAND_LCG_PARAM_B LCG incrementor
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* (4) m = RAND_LCG_PARAM_M + 1 LCG modulus
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*
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* (b) The pseudo-random number generated is in the range [0, RAND_LCG_PARAM_M].
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*
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See also 'lib_math.h RANDOM NUMBER DEFINES Note #1b'.
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*
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* (2) (a) IEEE Std 1003.1, 2004 Edition, Section 'rand() : DESCRIPTION' states that "rand()
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* ... need not be reentrant ... [and] is not required to be thread-safe".
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*
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* (b) However, Math_RandSeed() is re-entrant since it calculates the next random number
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* using ONLY local variables.
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*********************************************************************************************************
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*/
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RAND_NBR Math_RandSeed (RAND_NBR seed)
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{
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RAND_NBR rand_nbr;
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rand_nbr = (((RAND_NBR)RAND_LCG_PARAM_A * seed) + (RAND_NBR)RAND_LCG_PARAM_B) % ((RAND_NBR)RAND_LCG_PARAM_M + 1u);
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return (rand_nbr);
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}
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