Improved the seeding algorithm. Old behaviour can be achived by setting

2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>

	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c:
	Improved the seeding algorithm. Old behaviour can be achived by
	setting envvar G_RANDOM_VERSION to "2.0". (#99262)

	* docs/reference/glib/glib-docs.sgml,
	docs/reference/glib/Makefile.am: Renamed
	docs/reference/glib/changes-2.0.sgml to
	docs/reference/glib/changes.sgml and added section for changes
	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).

	* README.in, docs/reference/glib/running.sgml,
	docs/reference/glib/tmpl/random_numbers.sgml,
	docs/reference/glib/changes.sgml: Added notes about the new
	seeding algorithm.

ChangeLog

@@ -1,9 +1,24 @@
 2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>
 
+	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c: 
+	Changed the seeding algorithm. Old behaviour can be achived by
+	setting envvar G_RANDOM_VERSION to "2.0". (#99262)
+
+	* docs/reference/glib/glib-docs.sgml,
+	docs/reference/glib/Makefile.am: Renamed
+	docs/reference/glib/changes-2.0.sgml to
+	docs/reference/glib/changes.sgml and added section for changes
+	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).
+
+	* README.in, docs/reference/glib/running.sgml,
+	docs/reference/glib/tmpl/random_numbers.sgml,
+	docs/reference/glib/changes.sgml: Added notes about the new
+	seeding algorithm.
+
 	* configure.in: Make CPPFLAGS, not CFLAGS, include
 	G_THREAD_CFLAGS. CFLAGS is used while linking too and thus GLib
 	programs would link to the threads library on some platforms. Also
-	fixed a bug manifesting through this change.
+	fixed a bug manifesting through this change. (#77981)
 
 2002-11-26  Matthias Clasen  <maclas@gmx.de>
 

ChangeLog.pre-2-10

@@ -1,9 +1,24 @@
 2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>
 
+	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c: 
+	Changed the seeding algorithm. Old behaviour can be achived by
+	setting envvar G_RANDOM_VERSION to "2.0". (#99262)
+
+	* docs/reference/glib/glib-docs.sgml,
+	docs/reference/glib/Makefile.am: Renamed
+	docs/reference/glib/changes-2.0.sgml to
+	docs/reference/glib/changes.sgml and added section for changes
+	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).
+
+	* README.in, docs/reference/glib/running.sgml,
+	docs/reference/glib/tmpl/random_numbers.sgml,
+	docs/reference/glib/changes.sgml: Added notes about the new
+	seeding algorithm.
+
 	* configure.in: Make CPPFLAGS, not CFLAGS, include
 	G_THREAD_CFLAGS. CFLAGS is used while linking too and thus GLib
 	programs would link to the threads library on some platforms. Also
-	fixed a bug manifesting through this change.
+	fixed a bug manifesting through this change. (#77981)
 
 2002-11-26  Matthias Clasen  <maclas@gmx.de>
 

ChangeLog.pre-2-12

@@ -1,9 +1,24 @@
 2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>
 
+	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c: 
+	Changed the seeding algorithm. Old behaviour can be achived by
+	setting envvar G_RANDOM_VERSION to "2.0". (#99262)
+
+	* docs/reference/glib/glib-docs.sgml,
+	docs/reference/glib/Makefile.am: Renamed
+	docs/reference/glib/changes-2.0.sgml to
+	docs/reference/glib/changes.sgml and added section for changes
+	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).
+
+	* README.in, docs/reference/glib/running.sgml,
+	docs/reference/glib/tmpl/random_numbers.sgml,
+	docs/reference/glib/changes.sgml: Added notes about the new
+	seeding algorithm.
+
 	* configure.in: Make CPPFLAGS, not CFLAGS, include
 	G_THREAD_CFLAGS. CFLAGS is used while linking too and thus GLib
 	programs would link to the threads library on some platforms. Also
-	fixed a bug manifesting through this change.
+	fixed a bug manifesting through this change. (#77981)
 
 2002-11-26  Matthias Clasen  <maclas@gmx.de>
 

ChangeLog.pre-2-2

@@ -1,9 +1,24 @@
 2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>
 
+	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c: 
+	Changed the seeding algorithm. Old behaviour can be achived by
+	setting envvar G_RANDOM_VERSION to "2.0". (#99262)
+
+	* docs/reference/glib/glib-docs.sgml,
+	docs/reference/glib/Makefile.am: Renamed
+	docs/reference/glib/changes-2.0.sgml to
+	docs/reference/glib/changes.sgml and added section for changes
+	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).
+
+	* README.in, docs/reference/glib/running.sgml,
+	docs/reference/glib/tmpl/random_numbers.sgml,
+	docs/reference/glib/changes.sgml: Added notes about the new
+	seeding algorithm.
+
 	* configure.in: Make CPPFLAGS, not CFLAGS, include
 	G_THREAD_CFLAGS. CFLAGS is used while linking too and thus GLib
 	programs would link to the threads library on some platforms. Also
-	fixed a bug manifesting through this change.
+	fixed a bug manifesting through this change. (#77981)
 
 2002-11-26  Matthias Clasen  <maclas@gmx.de>
 

ChangeLog.pre-2-4

@@ -1,9 +1,24 @@
 2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>
 
+	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c: 
+	Changed the seeding algorithm. Old behaviour can be achived by
+	setting envvar G_RANDOM_VERSION to "2.0". (#99262)
+
+	* docs/reference/glib/glib-docs.sgml,
+	docs/reference/glib/Makefile.am: Renamed
+	docs/reference/glib/changes-2.0.sgml to
+	docs/reference/glib/changes.sgml and added section for changes
+	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).
+
+	* README.in, docs/reference/glib/running.sgml,
+	docs/reference/glib/tmpl/random_numbers.sgml,
+	docs/reference/glib/changes.sgml: Added notes about the new
+	seeding algorithm.
+
 	* configure.in: Make CPPFLAGS, not CFLAGS, include
 	G_THREAD_CFLAGS. CFLAGS is used while linking too and thus GLib
 	programs would link to the threads library on some platforms. Also
-	fixed a bug manifesting through this change.
+	fixed a bug manifesting through this change. (#77981)
 
 2002-11-26  Matthias Clasen  <maclas@gmx.de>
 

ChangeLog.pre-2-6

@@ -1,9 +1,24 @@
 2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>
 
+	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c: 
+	Changed the seeding algorithm. Old behaviour can be achived by
+	setting envvar G_RANDOM_VERSION to "2.0". (#99262)
+
+	* docs/reference/glib/glib-docs.sgml,
+	docs/reference/glib/Makefile.am: Renamed
+	docs/reference/glib/changes-2.0.sgml to
+	docs/reference/glib/changes.sgml and added section for changes
+	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).
+
+	* README.in, docs/reference/glib/running.sgml,
+	docs/reference/glib/tmpl/random_numbers.sgml,
+	docs/reference/glib/changes.sgml: Added notes about the new
+	seeding algorithm.
+
 	* configure.in: Make CPPFLAGS, not CFLAGS, include
 	G_THREAD_CFLAGS. CFLAGS is used while linking too and thus GLib
 	programs would link to the threads library on some platforms. Also
-	fixed a bug manifesting through this change.
+	fixed a bug manifesting through this change. (#77981)
 
 2002-11-26  Matthias Clasen  <maclas@gmx.de>
 

ChangeLog.pre-2-8

@@ -1,9 +1,24 @@
 2002-11-26  Sebastian Wilhelmi  <wilhelmi@ira.uka.de>
 
+	* glib/grand.c, gthread/gthread-impl.c, tests/rand-test.c: 
+	Changed the seeding algorithm. Old behaviour can be achived by
+	setting envvar G_RANDOM_VERSION to "2.0". (#99262)
+
+	* docs/reference/glib/glib-docs.sgml,
+	docs/reference/glib/Makefile.am: Renamed
+	docs/reference/glib/changes-2.0.sgml to
+	docs/reference/glib/changes.sgml and added section for changes
+	from 2.0 to 2.2 (Also corrected 1.0 to 1.2).
+
+	* README.in, docs/reference/glib/running.sgml,
+	docs/reference/glib/tmpl/random_numbers.sgml,
+	docs/reference/glib/changes.sgml: Added notes about the new
+	seeding algorithm.
+
 	* configure.in: Make CPPFLAGS, not CFLAGS, include
 	G_THREAD_CFLAGS. CFLAGS is used while linking too and thus GLib
 	programs would link to the threads library on some platforms. Also
-	fixed a bug manifesting through this change.
+	fixed a bug manifesting through this change. (#77981)
 
 2002-11-26  Matthias Clasen  <maclas@gmx.de>
 

README.in

@@ -24,6 +24,22 @@ Installation
 
 See the file 'INSTALL'
 
+Notes about GLib-2.2.0
+======================
+
+* GLib changed the seeding algorithm for the pseudo-random number
+  generator Mersenne Twister, as used by GRand and GRandom. This was
+  necessary, because some seeds would yield very bad pseudo-random
+  streams. Further information can be found at:
+
+          http://www.math.keio.ac.jp/~matumoto/emt.html
+
+  The original seeding algorithm, as found in GLib-2.0.x, can be used
+  instead of the new one by setting the environment variable
+  G_RANDOM_VERSION to the value of "2.0". Use the GLib-2.0 algorithm 
+  only if you have sequences of numbers generated with Glib-2.0 that 
+  you need to reproduce exactly.
+
 How to report bugs
 ==================
 

docs/reference/glib/Makefile.am

@@ -48,7 +48,7 @@ HTML_IMAGES =  				\
 content_files =				\
 	running.sgml			\
 	building.sgml			\
-	changes-2.0.sgml		\
+	changes.sgml			\
 	compiling.sgml			\
 	resources.sgml			\
 	version.xml

docs/reference/glib/changes.sgml

@@ -1,26 +1,58 @@
-<refentry id="glib-changes-2-0" revision="17 Jan 2002">
+<refentry id="glib-changes" revision="17 Jan 2002">
 <refmeta>
-<refentrytitle>Changes from 1.0 to 2.0</refentrytitle>
+<refentrytitle>Changes to GLib</refentrytitle>
 <manvolnum>3</manvolnum>
-<refmiscinfo>Changes from 1.0 to 2.0</refmiscinfo>
+<refmiscinfo>Changes to GLib</refmiscinfo>
 </refmeta>
 
 <refnamediv>
-<refname>Changes from 1.0 to 2.0</refname>
+<refname>Changes to GLib</refname>
 <refpurpose>
-Incompatible changes made between version 1.0 and version 2.0
+Incompatible changes made between successing versions of GLib
 </refpurpose>
 </refnamediv>
 
 
 <refsect1>
-<title>Incompatible changes from 1.0 to 2.0</title>
+<title>Incompatible changes from 2.0 to 2.2</title>
+
+<itemizedlist>
+
+<listitem>
+<para>
+GLib changed the seeding algorithm for the pseudo-random number
+generator Mersenne Twister, as used by <structname>GRand</structname>
+and <structname>GRandom</structname>. This was necessary, because some
+seeds would yield very bad pseudo-random streams.
+</para>
+
+<para>
+Further information can be found at the website of the Mersenne
+Twister random number generator at <ulink
+url="http://www.math.keio.ac.jp/~matumoto/emt.html">http://www.math.keio.ac.jp/~matumoto/emt.html</ulink>.
+</para> 
+
+<para>
+The original seeding algorithm, as found in GLib 2.0.x, can be used
+instead of the new one by setting the environment variable
+<envar>G_RANDOM_VERSION</envar> to the value of '2.0'. Use the
+GLib-2.0 algorithm only if you have sequences of numbers generated
+with Glib-2.0 that you need to reproduce exactly.
+</para> 
+</listitem>
+
+</itemizedlist>
+
+</refsect1>
+
+<refsect1>
+<title>Incompatible changes from 1.2 to 2.0</title>
 
 <para>
 The <ulink url="http://developer.gnome.org/dotplan/porting/">GNOME 2.0
 porting guide</ulink> on <ulink
 url="http://developer.gnome.org">http://developer.gnome.org</ulink>
-has some more detailed discussion of porting from 1.0 to 2.0.
+has some more detailed discussion of porting from 1.2 to 2.0.
 See the section on GLib.
 </para>
 

docs/reference/glib/glib-docs.sgml

@@ -58,7 +58,7 @@
 <!ENTITY glib-Building SYSTEM "building.sgml">
 <!ENTITY glib-Running SYSTEM "running.sgml">
 <!ENTITY glib-Resources SYSTEM "resources.sgml">
-<!ENTITY glib-Changes-2-0 SYSTEM "changes-2.0.sgml">
+<!ENTITY glib-Changes SYSTEM "changes.sgml">
 
 <!ENTITY version SYSTEM "version.xml">
 ]>
@@ -107,7 +107,7 @@ implementations, e.g. POSIX threads, DCE threads or Solaris threads.
     &glib-Building;
     &glib-Compiling;
     &glib-Running;
-    &glib-Changes-2-0;
+    &glib-Changes;
     &glib-Resources;
  
   </chapter> 

docs/reference/glib/running.sgml

@@ -62,6 +62,17 @@ variables like <envar>LANG</envar>, <envar>PATH</envar> or <envar>HOME</envar>.
   </para>
 </formalpara>
 
+<formalpara>
+  <title><envar>G_RANDOM_VERSION</envar></title>
+
+  <para>
+    If this environment variable is set to '2.0', the outdated
+    pseudo-random number seeding algorithm from GLib-2.0 is used
+    instead of the new better one. Use the GLib-2.0 algorithm only if
+    you have sequences of numbers generated with Glib-2.0 that you
+    need to reproduce exactly.
+  </para> 
+</formalpara> 
 </refsect2>
 
 <refsect2>

docs/reference/glib/tmpl/random_numbers.sgml

@@ -2,12 +2,12 @@
 Random Numbers
 
 <!-- ##### SECTION Short_Description ##### -->
-pseudo random number generator.
+pseudo-random number generator.
 
 <!-- ##### SECTION Long_Description ##### -->
 <para>
 The following functions allow you to use a portable, fast and good
-pseudo random number generator (PRNG). It uses the Mersenne Twister
+pseudo-random number generator (PRNG). It uses the Mersenne Twister
 PRNG, which was originally developed by Makoto Matsumoto and Takuji
 Nishimura. Further information can be found at <ulink
 url="http://www.math.keio.ac.jp/~matumoto/emt.html"
@@ -32,6 +32,18 @@ equally distributed random numbers, whereas for example the
 yield equally distributed numbers.
 </para>
 
+<para>
+GLib changed the seeding algorithm for the pseudo-random number
+generator Mersenne Twister, as used by <structname>GRand</structname>
+and <structname>GRandom</structname>. This was necessary, because some
+seeds would yield very bad pseudo-random streams. The original seeding
+algorithm, as found in GLib 2.0.x, can be used instead of the new one
+by setting the environment variable <envar>G_RANDOM_VERSION</envar> to
+the value of '2.0'. Use the GLib-2.0 algorithm only if you have
+sequences of numbers generated with Glib-2.0 that you need to
+reproduce exactly.  
+</para>
+
 <!-- ##### SECTION See_Also ##### -->
 <para>
 

glib/grand.c

@@ -58,6 +58,41 @@ static GRand* global_random = NULL;
 #define TEMPERING_SHIFT_T(y)  (y << 15)
 #define TEMPERING_SHIFT_L(y)  (y >> 18)
 
+static guint
+get_random_version (void)
+{
+  static gboolean initialized = FALSE;
+  static guint random_version;
+  
+  if (!initialized)
+    {
+      const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
+      if (!version_string || version_string[0] == '\000' || 
+	  strcmp (version_string, "2.2") == 0)
+	random_version = 22;
+      else if (strcmp (version_string, "2.0") == 0)
+	random_version = 20;
+      else
+	{
+	  g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
+		     version_string);
+	  random_version = 22;
+	}
+      initialized = TRUE;
+    }
+  
+  return random_version;
+}
+
+/* This is called from g_thread_init(). It's used to
+ * initialize some static data in a threadsafe way.
+ */
+void 
+g_rand_init (void)
+{
+  (void)get_random_version ();
+}
+
 struct _GRand
 {
   guint32 mt[N]; /* the array for the state vector  */
@@ -148,6 +183,9 @@ g_rand_set_seed (GRand* rand, guint32 seed)
 {
   g_return_if_fail (rand != NULL);
 
+  switch (get_random_version ())
+    {
+    case 20:
       /* setting initial seeds to mt[N] using         */
       /* the generator Line 25 of Table 1 in          */
       /* [KNUTH 1981, The Art of Computer Programming */
@@ -156,9 +194,24 @@ g_rand_set_seed (GRand* rand, guint32 seed)
       if (seed == 0) /* This would make the PRNG procude only zeros */
 	seed = 0x6b842128; /* Just set it to another number */
       
-  rand->mt[0]= seed & 0xffffffff;
+      rand->mt[0]= seed;
       for (rand->mti=1; rand->mti<N; rand->mti++)
-    rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]) & 0xffffffff;
+	rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
+      
+      break;
+    case 22:
+      /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
+      /* In the previous version (see above), MSBs of the    */
+      /* seed affect only MSBs of the array mt[].            */
+      
+      rand->mt[0]= seed;
+      for (rand->mti=1; rand->mti<N; rand->mti++)
+	rand->mt[rand->mti] = 1812433253UL * 
+	  (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti; 
+      break;
+    default:
+      g_assert_not_reached ();
+    }
 }
 
 /**

gthread/gthread-impl.c

@@ -66,6 +66,7 @@ void g_mutex_init (void);
 void g_mem_init (void);
 void g_messages_init (void);
 void g_convert_init (void);
+void g_rand_init (void);
 void g_main_thread_init (void);
 
 #define G_MUTEX_DEBUG_INFO(mutex) (*((gpointer*)(((char*)mutex)+G_MUTEX_SIZE)))
@@ -382,6 +383,7 @@ g_thread_init (GThreadFunctions* init)
   g_mem_init ();
   g_messages_init ();
   g_convert_init ();
+  g_rand_init ();
   g_main_thread_init ();
 
   /* now we can set g_threads_got_initialized and thus enable

tests/rand-test.c

@@ -6,26 +6,26 @@
 const gint32 first_numbers[] = 
 {
   0x7a7a7a7a,
-  0x20aea82a,
+  0xfdcc2d54,
-  0xcab337ab,
+  0x3a279ceb,
-  0xdcf770ea,
+  0xc4d39c33,
-  0xdf552b2f,
+  0xf31895cd,
-  0x32d1ef7f,
+  0x46ca0afc,
-  0x6bed6dd9,
+  0x3f5484ff,
-  0x7222df44,
+  0x54bc9557,
-  0x6b842128,
+  0xed2c24b1,
-  0x07f8579a,
+  0x84062503,
-  0x9dad1004,
+  0x8f6404b3,
-  0x2df264f2,
+  0x599a94b3,
-  0x13b48989,
+  0xe46d03d5,
-  0xf2929475,
+  0x310beb78,
-  0x30f30c97,
+  0x7bee5d08,
-  0x3f9a1ea7,
+  0x760d09be,
-  0x3bf04710,
+  0x59b6e163,
-  0xb85bd69e,
+  0xbf6d16ec,
-  0x790a48b0,
+  0xcca5fb54,
-  0xfa06b85f,
+  0x5de7259b,
-  0xa64cc9e3
+  0x1696330c,
 };
 
 const gint length = sizeof (first_numbers) / sizeof (first_numbers[0]);