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Add one to internal result of random number generator to avoid the value zero, from Freddie Chopin
git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5404 42af7a65-404d-4744-a932-0658087f49c3
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patacongo
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@ -3722,3 +3722,5 @@
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* include/nuttx/input/keypad.h, arch/arm/src/calypso/calypso_keypad.c, and
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configs/compal_e99/nsh_highram: First cut at a standard keypad interface
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definition. Contributed by Denis Carikli.
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* libc/stdlib/lib_rand.c: Always add one to result congruential generators
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to avoid the value zero. Suggested by Freddie Chopin.
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@ -389,7 +389,7 @@ nx11
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NOTES:
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1. If you do not have the call to sim_tcinitializE(0), the build
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1. If you do not have the call to sim_tcinitialize(0), the build
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will mysteriously fail claiming that is can't find up_tcenter()
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and up_tcleave(). That is a consequence of the crazy way that
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the simulation is built and can only be eliminated by calling
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@ -1,4 +1,4 @@
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/************************************************************
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/****************************************************************************
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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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@ -31,25 +31,21 @@
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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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/************************************************************
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* Compilation Switches
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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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****************************************************************************/
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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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/****************************************************************************
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* Pre-processor 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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# 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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@ -65,20 +61,16 @@
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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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# 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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# define RND_CONSTP RND2_CONSTP
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#else
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# define RND_CONSTP RND3_CONSTP
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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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/****************************************************************************
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* Private Function Prototypes
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************************************************************/
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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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@ -89,132 +81,133 @@ 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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* Private 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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static unsigned long g_randint1;
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#if (CONFIG_LIB_RAND_ORDER > 1)
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static unsigned long g_nRandInt2;
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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_nRandInt3;
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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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/****************************************************************************
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* Private Functions
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************************************************************/
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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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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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/* Get a random integer in the requested range */
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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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fRatio = frand1();
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ratio = frand1();
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#elif (CONFIG_LIB_RAND_ORDER == 2)
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fRatio = frand2();
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ratio = frand2();
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#else
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fRatio = frand3();
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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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nResult = (unsigned long)(((double_t)nLimit) * fRatio);
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/* Then, produce the return-able value */
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} while (nResult >= (unsigned long)nLimit);
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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)nResult;
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} /* end nrand */
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return (unsigned int)result;
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}
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static double_t frand1(void)
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{
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unsigned long nRandInt;
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unsigned long randint;
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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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/* First order congruential generator. One is added to the result of the
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* generated value to avoid the value zero which breaks the logic.
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*/
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randint = (RND1_CONSTK * g_randint1) % RND1_CONSTP + 1;
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g_randint1 = randint;
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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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return ((double_t)randint) / ((double_t)RND_CONSTP);
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}
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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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unsigned long randint;
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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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/* Second order congruential generator. One is added to the result of the
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* generated value to avoid the value zero which breaks the logic.
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*/
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randint = (RND2_CONSTK1 * g_randint1 +
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RND2_CONSTK2 * g_randint2) % RND2_CONSTP + 1;
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g_randint2 = g_randint1;
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g_randint1 = randint;
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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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return ((double_t)randint) / ((double_t)RND_CONSTP);
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}
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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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unsigned long randint;
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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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/* Third order congruential generator. One is added to the result of the
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* generated value to avoid the value zero which breaks the logic.
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*/
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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 + 1;
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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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/* 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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return ((double_t)randint) / ((double_t)RND_CONSTP);
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}
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#endif
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#endif
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/************************************************************
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/****************************************************************************
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* Public Functions
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************************************************************/
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/************************************************************
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****************************************************************************/
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/****************************************************************************
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* Function: srand, rand
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************************************************************/
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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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g_randint1 = seed;
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#if (CONFIG_LIB_RAND_ORDER > 1)
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g_nRandInt2 = seed;
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g_randint2 = 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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g_randint3 = 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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}
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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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}
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