Clean up bogosities in use of random(3) and srandom(3) --- do not assume
that RAND_MAX applies to them, since it doesn't. Instead add a config.h parameter MAX_RANDOM_VALUE. This is currently set at 2^31-1 but could be auto-configured if that ever proves necessary. Also fix some outright bugs like calling srand() where srandom() is appropriate.
This commit is contained in:
Tom Lane
parent
259489bab7
commit
9426047021
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@ -171,6 +171,18 @@
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<entry>convert floating point to integer</entry>
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<entry>integer(2.0)</entry>
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</row>
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<row>
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<entry>random()</entry>
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<entry>float8</entry>
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<entry>random value in the range 0.0 to 1.0</entry>
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<entry>random()</entry>
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</row>
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<row>
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<entry>setseed(float8)</entry>
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<entry>int</entry>
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<entry>set seed for subsequent random() calls</entry>
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<entry>setseed(0.54823)</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.46 2000/07/14 15:27:14 thomas Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.47 2000/08/07 00:51:18 tgl Exp $
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Postgres documentation
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-->
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@ -194,9 +194,9 @@ SET TIME ZONE { '<replaceable class="PARAMETER">timezone</replaceable>' | LOCAL
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<listitem>
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<para>
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The value for the seed to be used by the
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<function>random</function> catalog function. Significant
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<function>random</function> function. Allowed
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values are floating point numbers between 0 and 1, which
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are then multiplied by RAND_MAX. This product will
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are then multiplied by 2^31-1. This product will
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silently overflow if a number outside the range is used.
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</para>
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: geqo_main.c,v 1.22 2000/06/28 03:31:45 tgl Exp $
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* $Id: geqo_main.c,v 1.23 2000/08/07 00:51:23 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -106,9 +106,9 @@ geqo(Query *root)
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/* seed random number generator */
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/* XXX why is this done every time around? */
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if (Geqo_random_seed >= 0)
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srandom(Geqo_random_seed);
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srandom((unsigned int) Geqo_random_seed);
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else
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srandom(time(NULL));
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srandom((unsigned int) time(NULL));
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/* allocate genetic pool memory */
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pool = alloc_pool(pool_size, number_of_rels);
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@ -11,7 +11,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.158 2000/07/28 02:13:26 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.159 2000/08/07 00:51:30 tgl Exp $
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*
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* NOTES
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*
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@ -1850,7 +1850,7 @@ DoBackend(Port *port)
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*/
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random_seed = 0;
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gettimeofday(&now, &tz);
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srandom(now.tv_usec);
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srandom((unsigned int) now.tv_usec);
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/* ----------------
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* Now, build the argv vector that will be given to PostgresMain.
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@ -2029,7 +2029,6 @@ RandomSalt(char *salt)
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static long
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PostmasterRandom(void)
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{
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static bool initialized = false;
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if (!initialized)
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.67 2000/08/01 18:29:35 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.68 2000/08/07 00:51:14 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1315,7 +1315,7 @@ drandom(PG_FUNCTION_ARGS)
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float8 result;
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/* result 0.0-1.0 */
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result = ((double) random()) / RAND_MAX;
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result = ((double) random()) / ((double) MAX_RANDOM_VALUE);
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PG_RETURN_FLOAT8(result);
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}
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@ -1328,7 +1328,7 @@ Datum
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setseed(PG_FUNCTION_ARGS)
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{
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float8 seed = PG_GETARG_FLOAT8(0);
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int iseed = (seed * RAND_MAX);
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int iseed = (int) (seed * MAX_RANDOM_VALUE);
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srandom((unsigned int) iseed);
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.19 2000/06/05 07:28:52 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.20 2000/08/07 00:51:14 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -45,15 +45,18 @@ nonnullvalue(PG_FUNCTION_ARGS)
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/*
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* oidrand (oid o, int4 X)-
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* takes in an oid and a int4 X, and will return 'true'
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* about 1/X of the time.
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* Takes in an oid and a int4 X, and will return 'true' about 1/X of
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* the time. If X == 0, this will always return true.
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* Useful for doing random sampling or subsetting.
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* if X == 0, this will always return true;
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*
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* Example use:
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* select * from TEMP where oidrand(TEMP.oid, 10)
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* will return about 1/10 of the tuples in TEMP
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*
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* NOTE: the OID input is not used at all. It is there just because of
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* an old optimizer bug: a qual expression containing no variables was
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* mistakenly assumed to be a constant. Pretending to access the row's OID
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* prevented the optimizer from treating the oidrand() result as constant.
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*/
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static bool random_initialized = false;
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@ -61,7 +64,6 @@ static bool random_initialized = false;
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Datum
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oidrand(PG_FUNCTION_ARGS)
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{
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/* XXX seems like we ought to be using the oid for something? */
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#ifdef NOT_USED
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Oid o = PG_GETARG_OID(0);
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#endif
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@ -96,7 +98,7 @@ oidsrand(PG_FUNCTION_ARGS)
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{
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int32 X = PG_GETARG_INT32(0);
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srand(X);
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srandom((unsigned int) X);
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random_initialized = true;
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PG_RETURN_BOOL(true);
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}
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@ -8,7 +8,7 @@
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* or in config.h afterwards. Of course, if you edit config.h, then your
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* changes will be overwritten the next time you run configure.
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*
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* $Id: config.h.in,v 1.128 2000/07/28 02:13:40 tgl Exp $
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* $Id: config.h.in,v 1.129 2000/08/07 00:51:38 tgl Exp $
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*/
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#ifndef CONFIG_H
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@ -484,6 +484,15 @@ extern long random(void);
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extern void srandom(unsigned int seed);
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#endif
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/* The random() function is expected to yield values 0 .. MAX_RANDOM_VALUE */
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/* Currently, all known implementations yield 0..2^31-1, so we just hardwire
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* this constant. We could do a configure test if it proves to be necessary.
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* CAUTION: Think not to replace this with RAND_MAX. RAND_MAX defines the
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* maximum value of the older rand() function, which is often different from
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* --- and considerably inferior to --- random().
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*/
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#define MAX_RANDOM_VALUE (0x7FFFFFFF)
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/* Set to 1 if you have libz.a */
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#undef HAVE_LIBZ
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@ -6,7 +6,7 @@
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: geqo_random.h,v 1.6 2000/01/26 05:58:20 momjian Exp $
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* $Id: geqo_random.h,v 1.7 2000/08/07 00:51:42 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -26,13 +26,13 @@
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#include <math.h>
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#define GEQOMASK 2147483647
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/* geqo_rand returns a random float value between 0 and 1 inclusive */
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#define geqo_rand() ((double)random()/GEQOMASK)
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#define geqo_rand() (((double) random()) / ((double) MAX_RANDOM_VALUE))
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/* geqo_randint returns integer value
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between lower and upper inclusive */
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/* geqo_randint returns integer value between lower and upper inclusive */
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#define geqo_randint(upper,lower) ( (int) floor( geqo_rand()*((upper-lower)+0.999999) ) + lower )
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#define geqo_randint(upper,lower) \
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( (int) floor( geqo_rand()*(((upper)-(lower))+0.999999) ) + (lower) )
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#endif /* GEQO_RANDOM_H */
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