From 81fd4c05214b7660ad287dc964b3640e127b83a8 Mon Sep 17 00:00:00 2001
From: Tobias Fuchs <fuchs.tobias.ext@siemens.com>
Date: Mon, 23 Feb 2015 17:14:50 +0100
Subject: [PATCH] algorithms_cpp: using block size partitioner in ForEach

---
 algorithms_cpp/include/embb/algorithms/internal/for_each-inl.h | 65 ++++++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 38 insertions(+), 27 deletions(-)

diff --git a/algorithms_cpp/include/embb/algorithms/internal/for_each-inl.h b/algorithms_cpp/include/embb/algorithms/internal/for_each-inl.h
index c1d0c6c..d14dc87 100644
--- a/algorithms_cpp/include/embb/algorithms/internal/for_each-inl.h
+++ b/algorithms_cpp/include/embb/algorithms/internal/for_each-inl.h
@@ -47,48 +47,54 @@ class ForEachFunctor {
   /**
    * Constructs a for-each functor with arguments.
    */
-  ForEachFunctor(RAI first, RAI last, Function unary,
-    const embb::mtapi::ExecutionPolicy& policy, size_t block_size)
-    : first_(first), last_(last), unary_(unary), policy_(policy),
-      block_size_(block_size) {
+  ForEachFunctor(size_t chunk_first, size_t chunk_last, Function unary,
+                 const embb::mtapi::ExecutionPolicy& policy, 
+                 const BlockSizePartitioner<RAI>& partitioner)
+  : chunk_first_(chunk_first), chunk_last_(chunk_last), 
+    unary_(unary), policy_(policy), partitioner_(partitioner) {
   }
 
-  void Action(mtapi::TaskContext& context) {
-    size_t distance = static_cast<size_t>(std::distance(first_, last_));
-    if (distance == 0) return;
-    if (distance <= block_size_) {  // leaf case -> do work
-      for (RAI it = first_; it != last_; ++it) {
+  void Action(mtapi::TaskContext&) {
+    if (chunk_first_ == chunk_last_) {
+      // Leaf case, recursed to single chunk. Do work on chunk:
+      ChunkDescriptor<RAI> chunk = partitioner_[chunk_first_];
+      RAI first = chunk.GetFirst();
+      RAI last  = chunk.GetLast();
+      for (RAI it = first; it != last; ++it) {
         unary_(*it);
       }
-    } else {  // recurse further
-      ChunkPartitioner<RAI> partitioner(first_, last_, 2);
-      ChunkDescriptor<RAI> chunk_l = partitioner[0];
-      ChunkDescriptor<RAI> chunk_r = partitioner[1];
-      self_t functor_l(chunk_l.GetFirst(),
-                       chunk_l.GetLast(),
-                       unary_, policy_, block_size_);
-      self_t functor_r(chunk_r.GetFirst(),
-                       chunk_r.GetLast(),
-                       unary_, policy_, block_size_);
-      // Spawn tasks for right partition first:
+    }
+    else {
+      // Recurse further:
+      size_t chunk_split_index = (chunk_first_ + chunk_last_) / 2;
+      // Split chunks into left / right branches:
+      self_t functor_l(chunk_first_, 
+                       chunk_split_index,
+                       unary_, policy_, partitioner_);
+      self_t functor_r(chunk_split_index + 1, 
+                       chunk_last_,
+                       unary_, policy_, partitioner_);
+      mtapi::Task task_l = mtapi::Node::GetInstance().Spawn(
+        mtapi::Action(
+          base::MakeFunction(
+          functor_l, &ForEachFunctor<RAI, Function>::Action), 
+          policy_));
       mtapi::Task task_r = mtapi::Node::GetInstance().Spawn(
         mtapi::Action(
           base::MakeFunction(
           functor_r, &ForEachFunctor<RAI, Function>::Action), 
           policy_));
-      // Recurse on left partition:
-      functor_l.Action(context);
-      // Wait for tasks on right partition to complete:
       task_r.Wait(MTAPI_INFINITE);
+      task_l.Wait(MTAPI_INFINITE);
     }
   }
 
  private:
-  RAI first_;
-  RAI last_;
+  size_t chunk_first_;
+  size_t chunk_last_;
   Function unary_;
   const embb::mtapi::ExecutionPolicy& policy_;
-  size_t block_size_;
+  const BlockSizePartitioner<RAI>& partitioner_;
 
   /**
    * Disables assignment.
@@ -112,12 +118,17 @@ void ForEachRecursive(RAI first, RAI last, Function unary,
       block_size = 1;
     }
   }
+
   // Perform check of task number sufficiency
   if (((distance / block_size) * 2) + 1 > MTAPI_NODE_MAX_TASKS_DEFAULT) {
     EMBB_THROW(embb::base::ErrorException, "Not enough MTAPI tasks available "
                "to perform the parallel foreach loop");
   }
-  ForEachFunctor<RAI, Function> functor(first, last, unary, policy, block_size);
+
+  BlockSizePartitioner<RAI> partitioner(first, last, block_size);
+  ForEachFunctor<RAI, Function> functor(0, 
+                                        partitioner.Size() - 1, 
+                                        unary, policy, partitioner);
   mtapi::Task task = node.Spawn(mtapi::Action(
                      base::MakeFunction(functor,
                        &ForEachFunctor<RAI, Function>::Action),
--
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