From: Johannes Singler <singler@kit.edu>
Date: Tue, 30 Mar 2010 14:50:56 +0000 (+0000)
Subject: random_shuffle.h (__parallel_random_shuffle_drs): Take as many threads as possible, i.
X-Git-Tag: releases/gcc-4.5.0~160
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=26e020539c3d5bc0831d0443e38a9f0ed37620a7;p=thirdparty%2Fgcc.git

random_shuffle.h (__parallel_random_shuffle_drs): Take as many threads as possible, i.

2010-03-30  Johannes Singler  <singler@kit.edu>

        * include/parallel/random_shuffle.h
        (__parallel_random_shuffle_drs) : Take as many threads as
        possible, i. e. favor parallelism over cache efficiency.
        Use own PRNG also for the 1 thread case.

From-SVN: r157826
---

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 06457d8bd728..adf53ceac76c 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2010-03-30  Johannes Singler  <singler@kit.edu>
+
+        * include/parallel/random_shuffle.h
+        (__parallel_random_shuffle_drs) : Take as many threads as
+        possible, i. e. favor parallelism over cache efficiency.
+        Use own PRNG also for the 1 thread case.
+
 2010-03-30  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* include/debug/unordered_map: Clean-up includes and guards.
diff --git a/libstdc++-v3/include/parallel/random_shuffle.h b/libstdc++-v3/include/parallel/random_shuffle.h
index 3082ea8dbc03..baad24d4f664 100644
--- a/libstdc++-v3/include/parallel/random_shuffle.h
+++ b/libstdc++-v3/include/parallel/random_shuffle.h
@@ -322,10 +322,16 @@ namespace __gnu_parallel
 	}
 #endif
 
-      __num_threads = std::min<_BinIndex>(__num_threads, __num_bins);
+      __num_bins = __round_up_to_pow2(
+                        std::max<_BinIndex>(__num_threads, __num_bins));
 
       if (__num_threads <= 1)
-	return __sequential_random_shuffle(__begin, __end, __rng);
+      {
+        _RandomNumber __derived_rng(
+                            __rng(std::numeric_limits<uint32_t>::max()));
+	__sequential_random_shuffle(__begin, __end, __derived_rng);
+        return;
+      }
 
       _DRandomShufflingGlobalData<_RAIter> __sd(__begin);
       _DRSSorterPU<_RAIter, _RandomNumber >* __pus;