From: Johannes Singler <singler@kit.edu>
Date: Tue, 8 Jun 2010 09:11:49 +0000 (+0000)
Subject: 2010-06-08  Johannes Singler  <singler@kit.edu>
X-Git-Tag: releases/gcc-4.6.0~6678
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=736cc331c60f5ce97001b386d5af44076549f086;p=thirdparty%2Fgcc.git

2010-06-08  Johannes Singler  <singler@kit.edu>

        * include/parallel/partial_sum.h
        (__parallel_partial_sum_linear):
        Correctly calculate part lengths for partial_sum_dilation!=1.0f.

From-SVN: r160428
---

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 0f24ab4f6e7c..3ebfd13bac37 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,9 @@
+2010-06-08  Johannes Singler  <singler@kit.edu>
+
+        * include/parallel/partial_sum.h
+        (__parallel_partial_sum_linear):
+        Correctly calculate part lengths for partial_sum_dilation!=1.
+
 2010-06-07  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR libstdc++/44417
diff --git a/libstdc++-v3/include/parallel/partial_sum.h b/libstdc++-v3/include/parallel/partial_sum.h
index 966d9db05727..d398c4585a25 100644
--- a/libstdc++-v3/include/parallel/partial_sum.h
+++ b/libstdc++-v3/include/parallel/partial_sum.h
@@ -127,10 +127,13 @@ namespace __gnu_parallel
 	    equally_split(__n, __num_threads + 1, __borders);
 	  else
 	    {
+	      _DifferenceType __first_part_length =
+		  std::max<_DifferenceType>(1,
+		    __n / (1.0f + __s.partial_sum_dilation * __num_threads));
 	      _DifferenceType __chunk_length =
-		((double)__n
-		 / ((double)__num_threads + __s.partial_sum_dilation)),
-		__borderstart = __n - __num_threads * __chunk_length;
+		  (__n - __first_part_length) / __num_threads;
+	      _DifferenceType __borderstart =
+		  __n - __num_threads * __chunk_length;
 	      __borders[0] = 0;
 	      for (_ThreadIndex __i = 1; __i < (__num_threads + 1); ++__i)
 		{