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

        * include/parallel/find.h
        (__find_template(.., growing_blocks_tag)): Make block size
        proportional to current position.
        * include/parallel/settings.h (_Settings): Introduce new tuning
        parameter find_scale_factor to the end of the struct, defaults to
        0.01f.

From-SVN: r160439

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 3ebfd13bac37e739ad6cb4154e68552d1efe9e11..aa2e5bda671ccca829d96b8f055824499957614e 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,12 @@
+2010-06-08  Johannes Singler  <singler@kit.edu>
+
+        * include/parallel/find.h
+        (__find_template(.., growing_blocks_tag)): Make block size
+        proportional to current position.
+        * include/parallel/settings.h (_Settings): Introduce new tuning
+        parameter find_scale_factor to the end of the struct, defaults to
+        0.01f.
+
 2010-06-08  Johannes Singler  <singler@kit.edu>
 
         * include/parallel/partial_sum.h

diff --git a/libstdc++-v3/include/parallel/find.h b/libstdc++-v3/include/parallel/find.h
index b4e581488ae36a471ee1af44aee3413436c1dcb9..eb37d8aace18d80cec3f52f5cb113af8de643387 100644 (file)
--- a/libstdc++-v3/include/parallel/find.h
+++ b/libstdc++-v3/include/parallel/find.h
@@ -168,9 +168,7 @@ namespace __gnu_parallel
    *  @param __selector _Functionality (e. g. std::find_if(), std::equal(),...)
    *  @return Place of finding in both sequences.
    *  @see __gnu_parallel::_Settings::find_sequential_search_size
-   *  @see __gnu_parallel::_Settings::find_initial_block_size
-   *  @see __gnu_parallel::_Settings::find_maximum_block_size
-   *  @see __gnu_parallel::_Settings::find_increasing_factor
+   *  @see __gnu_parallel::_Settings::find_scale_factor
    *
    *  There are two main differences between the growing blocks and
    *  the constant-size blocks variants.
@@ -218,6 +216,8 @@ namespace __gnu_parallel
       omp_lock_t __result_lock;
       omp_init_lock(&__result_lock);
 
+      const float __scale_factor = __s.find_scale_factor;
+
       _ThreadIndex __num_threads = __get_max_threads();
 #     pragma omp parallel shared(__result) num_threads(__num_threads)
       {
@@ -227,7 +227,8 @@ namespace __gnu_parallel
        // Not within first __k elements -> start parallel.
        _ThreadIndex __iam = omp_get_thread_num();
 
-       _DifferenceType __block_size = __s.find_initial_block_size;
+       _DifferenceType __block_size =
+         std::max<_DifferenceType>(1, __scale_factor * __next_block_start);
        _DifferenceType __start = __fetch_and_add<_DifferenceType>
          (&__next_block_start, __block_size);
 
@@ -265,15 +266,14 @@ namespace __gnu_parallel
                omp_unset_lock(&__result_lock);
              }
 
-           __block_size = std::min<_DifferenceType>
-             (__block_size * __s.find_increasing_factor,
-              __s.find_maximum_block_size);
+           _DifferenceType __block_size =
+            std::max<_DifferenceType>(1, __scale_factor * __next_block_start);
 
            // Get new block, update pointer to next block.
            __start = __fetch_and_add<_DifferenceType>(&__next_block_start,
                                                       __block_size);
-           __stop = (__length < (__start + __block_size)
-                     ? __length : (__start + __block_size));
+           __stop =
+             std::min<_DifferenceType>(__length, __start + __block_size);
          }
       } //parallel
 

diff --git a/libstdc++-v3/include/parallel/settings.h b/libstdc++-v3/include/parallel/settings.h
index 3b326ff8e4746df90df54d803a5b1f83af7d5c34..5d00b02694446d3eca7881c1a93c0eaa0cb0d9bd 100644 (file)
--- a/libstdc++-v3/include/parallel/settings.h
+++ b/libstdc++-v3/include/parallel/settings.h
@@ -272,6 +272,9 @@ namespace __gnu_parallel
     /// Minimal input size for search and search_n.
     _SequenceIndex              search_minimal_n;
 
+    /// Block size scale-down factor with respect to current position.
+    float                       find_scale_factor;
+
     /// Get the global settings.
     _GLIBCXX_CONST static const _Settings&
     get() throw();
@@ -331,7 +334,8 @@ namespace __gnu_parallel
             TLB_size(128),
             cache_line_size(64),
             qsb_steals(0),
-            search_minimal_n(1000)
+            search_minimal_n(1000),
+            find_scale_factor(0.01f)
     { }
   };
 }