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Commit655473a

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Add commentary about Cygwin's broken erand48, per report from Andrew Dunstan.
1 parentdc7aa36 commit655473a

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3 files changed

+20
-10
lines changed

3 files changed

+20
-10
lines changed

‎configure

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -19085,7 +19085,8 @@ esac
1908519085

1908619086
fi
1908719087

19088-
# Cygwin's erand48 sometimes hangs, so force use of ours
19088+
# Cygwin's erand48() is broken (always returns zero) in some releases,
19089+
# so force use of ours.
1908919090
if test "$PORTNAME" = "cygwin"; then
1909019091
case " $LIBOBJS " in
1909119092
*" erand48.$ac_objext "* ) ;;

‎configure.in

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
dnl Process this file with autoconf to produce a configure script.
2-
dnl $PostgreSQL: pgsql/configure.in,v 1.606 2009/07/23 23:50:29 adunstan Exp $
2+
dnl $PostgreSQL: pgsql/configure.in,v 1.607 2009/07/24 15:03:07 tgl Exp $
33
dnl
44
dnl Developers, please strive to achieve this order:
55
dnl
@@ -1289,7 +1289,8 @@ if test "$PORTNAME" = "solaris"; then
12891289
AC_LIBOBJ(getopt)
12901290
fi
12911291

1292-
# Cygwin's erand48 sometimes hangs, so force use of ours
1292+
# Cygwin's erand48() is broken (always returns zero) in some releases,
1293+
# so force use of ours.
12931294
if test "$PORTNAME" = "cygwin"; then
12941295
AC_LIBOBJ(erand48)
12951296
fi

‎src/backend/optimizer/geqo/geqo_selection.c

Lines changed: 15 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
9-
* $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_selection.c,v 1.25 2009/07/16 20:55:44 tgl Exp $
9+
* $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_selection.c,v 1.26 2009/07/24 15:03:07 tgl Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -42,7 +42,7 @@
4242
#include"optimizer/geqo_random.h"
4343
#include"optimizer/geqo_selection.h"
4444

45-
staticintlinear(PlannerInfo*root,intmax,doublebias);
45+
staticintlinear_rand(PlannerInfo*root,intmax,doublebias);
4646

4747

4848
/*
@@ -57,21 +57,29 @@ geqo_selection(PlannerInfo *root, Chromosome *momma, Chromosome *daddy,
5757
intfirst,
5858
second;
5959

60-
first=linear(root,pool->size,bias);
61-
second=linear(root,pool->size,bias);
60+
first=linear_rand(root,pool->size,bias);
61+
second=linear_rand(root,pool->size,bias);
6262

63+
/*
64+
* Ensure we have selected different genes, except if pool size is only
65+
* one, when we can't.
66+
*
67+
* This code has been observed to hang up in an infinite loop when the
68+
* platform's implementation of erand48() is broken. We consider that a
69+
* feature: it lets you know you'd better fix the random-number generator.
70+
*/
6371
if (pool->size>1)
6472
{
6573
while (first==second)
66-
second=linear(root,pool->size,bias);
74+
second=linear_rand(root,pool->size,bias);
6775
}
6876

6977
geqo_copy(root,momma,&pool->data[first],pool->string_length);
7078
geqo_copy(root,daddy,&pool->data[second],pool->string_length);
7179
}
7280

7381
/*
74-
*linear
82+
*linear_rand
7583
* generates random integer between 0 and input max number
7684
* using input linear bias
7785
*
@@ -81,7 +89,7 @@ geqo_selection(PlannerInfo *root, Chromosome *momma, Chromosome *daddy,
8189
* bias = (prob of first rule) / (prob of middle rule)
8290
*/
8391
staticint
84-
linear(PlannerInfo*root,intpool_size,doublebias)
92+
linear_rand(PlannerInfo*root,intpool_size,doublebias)
8593
{
8694
doubleindex;/* index between 0 and pop_size */
8795
doublemax= (double)pool_size;

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