Merge pull request #352 from PDLPorters/pdl-srand-seed-func

Add pdl_seed() function that uses PID and epoch time
PDLPorters · Nov 19, 2021 · f1b8b80 · f1b8b80
2 parents 708c3ee + a1d56f7
commit f1b8b80
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Showing 5 changed files with 35 additions and 7 deletions.
diff --git a/Basic/Core/Core.xs b/Basic/Core/Core.xs
@@ -212,6 +212,13 @@ _inf(...)
 
 MODULE = PDL::Core     PACKAGE = PDL::Core
 
+IV
+seed()
+  CODE:
+    RETVAL = pdl_pdl_seed();
+  OUTPUT:
+    RETVAL
+
 int
 online_cpus()
   CODE:

diff --git a/Basic/Core/pdlcore.c b/Basic/Core/pdlcore.c
@@ -1190,3 +1190,23 @@ pdl_slice_args* pdl_slice_args_parse(SV* sv) {
   PDLDEBUG_f(pdl_dump_slice_args(retval));
   return retval;
 }
+
+/* pdl_seed() - prefix as "seed" #define-d by Perl
+ *
+ * Used to seed PDL's built-in RNG.
+ */
+uint64_t pdl_pdl_seed() {
+	/* This implementation is from section 7.1 Seeding of
+	 *
+	 * Helmut G. Katzgraber. "Random Numbers in Scientific Computing:
+	 * An Introduction". <https://arxiv.org/abs/1005.4117v1>.
+	 */
+	uint64_t s, pid;
+	/* Start of Perl-specific symbols */
+	Time_t seconds;
+	pid = (uint64_t)PerlProc_getpid();
+	(void)time(&seconds);
+	/* End of Perl-specific symbols */
+	s = (uint64_t)seconds;
+	return abs(((s*181)*((pid-83)*359))%104729);
+}
diff --git a/Basic/Core/pdlcore.h b/Basic/Core/pdlcore.h
@@ -12,6 +12,8 @@
 #include "XSUB.h"  /* for the win32 perlCAPI crap */
 #include "ppport.h"  /* include this AFTER XSUB.h */
 
+#include <stdint.h>
+
 #if defined(CONTEXT) && defined(__osf__)
 #undef CONTEXT
 #endif
@@ -127,7 +129,8 @@ void pdl_readdata_vaffine(pdl *it);
   X(slice_args_parse_string, pdl_slice_args, ( char* )) \
   X(slice_args_parse, pdl_slice_args*, ( SV* )) \
   X(online_cpus, int, ()) \
-  X(magic_get_thread, int, (pdl *))
+  X(magic_get_thread, int, (pdl *)) \
+  X(pdl_seed, uint64_t, ())
 
 /*************** Function prototypes *********************/
 #define X(sym, rettype, args) \

diff --git a/Basic/Primitive/primitive.pd b/Basic/Primitive/primitive.pd
@@ -2008,7 +2008,7 @@ void pdl_srand(uint64_t **s, uint64_t seed, int n);
 double pdl_drand(uint64_t *s);
 #define PDL_MAYBE_SRAND \
   if (pdl_srand_threads < 0) \
-    pdl_srand(&pdl_rand_state, (uint64_t)time(NULL), PDL->online_cpus());
+    pdl_srand(&pdl_rand_state, PDL->pdl_seed(), PDL->online_cpus());
 #define PDL_RAND_SET_OFFSET(v, thr, pdl) \
   if (v < 0) \
     v = thr.mag_nthr >= 0 ? PDL->magic_get_thread(pdl) % PDL->online_cpus() : 0
@@ -2038,11 +2038,7 @@ L<PDL::Core/online_cpus>.
 EOF
 	PMCode=><<'EOD',
 *srand = \&PDL::srand;
-sub PDL::srand {
-   my $pdl = shift;
-   $pdl //= longlong(time);
-   PDL::_srand_int($pdl);
-}
+sub PDL::srand { PDL::_srand_int($_[0] // PDL::Core::seed()) }
 EOD
 );
 

diff --git a/Changes b/Changes
@@ -1,3 +1,5 @@
+- PDL::Core::seed - thanks @zmughal
+
 2.062 2021-11-19
 - Primitive::srand() added, random() calls if not done yet - thanks @whumann for report
 - Primitive::random() et al to use xoroshiro256plus instead of Perl's rand()