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.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@160428 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 0f24ab4..3ebfd13 100644 (file)
--- 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 966d9db..d398c45 100644 (file)
--- 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)
                {