Use distributed::copy() algorithm in distributed::vector

include/boost/compute/distributed/copy.hpp

@@ -27,12 +27,20 @@
 
 #include <boost/compute/distributed/context.hpp>
 #include <boost/compute/distributed/command_queue.hpp>
-#include <boost/compute/distributed/vector.hpp>
+#include <boost/compute/distributed/detail/weight_func.hpp>
 
 namespace boost {
 namespace compute {
 namespace distributed {
 
+// forward declaration for distributed::vector
+template<
+    class T,
+    weight_func weight,
+    class Alloc
+>
+class vector;
+
 namespace detail {
 
 template<class T>

include/boost/compute/distributed/detail/weight_func.hpp

@@ -0,0 +1,79 @@
+//---------------------------------------------------------------------------//
+// Copyright (c) 2016 Jakub Szuppe <j.szuppe@gmail.com>
+//
+// Distributed under the Boost Software License, Version 1.0
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+//
+// See http://boostorg.github.com/compute for more information.
+//---------------------------------------------------------------------------//
+
+#ifndef BOOST_COMPUTE_DETAIL_WEIGHT_FUNC_HPP
+#define BOOST_COMPUTE_DETAIL_WEIGHT_FUNC_HPP
+
+#include <vector>
+
+#include <boost/compute/distributed/context.hpp>
+#include <boost/compute/distributed/command_queue.hpp>
+
+namespace boost {
+namespace compute {
+namespace distributed {
+
+typedef std::vector<double> (*weight_func)(const command_queue&);
+
+namespace detail {
+
+/// \internal_
+/// Rounds up \p n to the nearest multiple of \p m.
+/// Note: \p m must be a multiple of 2.
+size_t round_up(size_t n, size_t m)
+{
+    assert(m && ((m & (m -1)) == 0));
+    return (n + m - 1) & ~(m - 1);
+}
+
+/// \internal_
+///
+std::vector<size_t> partition(const command_queue& queue,
+                              weight_func weight_func,
+                              const size_t size,
+                              const size_t align)
+{
+    std::vector<double> weights = weight_func(queue);
+    std::vector<size_t> partition;
+    partition.reserve(queue.size() + 1);
+    partition.push_back(0);
+
+    if(queue.size() > 1)
+    {
+        double acc = 0;
+        for(size_t i = 0; i < queue.size(); i++)
+        {
+            acc += weights[i];
+            partition.push_back(
+                std::min(
+                    size,
+                    round_up(size * acc, align)
+                )
+            );
+        }
+        return partition;
+    }
+    partition.push_back(size);
+    return partition;
+}
+
+} // end distributed detail
+
+std::vector<double> default_weight_func(const command_queue& queue)
+{
+    return std::vector<double>(queue.size(), 1.0/queue.size());
+}
+
+} // end distributed namespace
+} // end compute namespace
+} // end boost namespace
+
+
+#endif /* INCLUDE_BOOST_COMPUTE_DETAIL_WEIGHT_FUNC_HPP_ */