From ac9aa47bbc3ab6a6921c2df9d2430bc054196be6 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Mon, 23 Jun 2008 15:50:28 +0000
Subject: [PATCH] optimize linear vectorization both in Assign and Sum (optimal
 amortized perf)

---
 Eigen/src/Core/Assign.h | 17 +++++++++++------
 Eigen/src/Core/Sum.h    | 35 +++++++++++++----------------------
 2 files changed, 24 insertions(+), 28 deletions(-)

diff --git a/Eigen/src/Core/Assign.h b/Eigen/src/Core/Assign.h
index 63eda1e85..c28a0371b 100644
--- a/Eigen/src/Core/Assign.h
+++ b/Eigen/src/Core/Assign.h
@@ -307,12 +307,17 @@ struct ei_assign_impl<Derived1, Derived2, LinearVectorization, NoUnrolling>
     int index = 0;
 
     // do the vectorizable part of the assignment
-    for ( ; index<alignedSize ; index+=packetSize)
+    int row = 0;
+    int col = 0;
+    while (index<alignedSize)
     {
-      // FIXME the following is not really efficient
-      const int row = rowMajor ? index/innerSize : index%innerSize;
-      const int col = rowMajor ? index%innerSize : index/innerSize;
-      dst.template writePacket<Aligned>(row, col, src.template packet<Aligned>(row, col));
+      int start = rowMajor ? col : row;
+      int end = std::min(innerSize, start + alignedSize-index);
+      for ( ; (rowMajor ? col : row)<end; (rowMajor ? col : row)+=packetSize)
+        dst.template writePacket<Aligned>(row, col, src.template packet<Aligned>(row, col));
+      index += (rowMajor ? col : row) - start;
+      row = rowMajor ? index/innerSize : index%innerSize;
+      col = rowMajor ? index%innerSize : index/innerSize;
     }
 
     // now we must do the rest without vectorization.
@@ -380,7 +385,7 @@ struct ei_assign_impl<Derived1, Derived2, SliceVectorization, NoUnrolling>
     const int innerSize = rowMajor ? dst.cols() : dst.rows();
     const int outerSize = rowMajor ? dst.rows() : dst.cols();
     const int alignedInnerSize = (innerSize/packetSize)*packetSize;
-    
+
     for(int i = 0; i < outerSize; i++)
     {
       // do the vectorizable part of the assignment
diff --git a/Eigen/src/Core/Sum.h b/Eigen/src/Core/Sum.h
index c6b7cacce..d638f0979 100644
--- a/Eigen/src/Core/Sum.h
+++ b/Eigen/src/Core/Sum.h
@@ -54,7 +54,7 @@ public:
     Unrolling = Cost <= UnrollingLimit
               ? CompleteUnrolling
               : NoUnrolling
-  };       
+  };
 };
 
 /***************************************************************************
@@ -62,7 +62,7 @@ public:
 ***************************************************************************/
 
 /*** no vectorization ***/
- 
+
 template<typename Derived, int Start, int Length>
 struct ei_sum_novec_unroller
 {
@@ -194,32 +194,23 @@ struct ei_sum_impl<Derived, LinearVectorization, NoUnrolling>
     // do the vectorizable part of the sum
     if(size >= packetSize)
     {
-    asm("#begin");
-
       PacketScalar packet_res;
       packet_res = mat.template packet<Aligned>(0, 0);
-      int index;
-      if(Derived::IsVectorAtCompileTime)
+      int row = 0;
+      int col = 0;
+      int index = packetSize;
+      while (index<alignedSize)
       {
-        for(index = packetSize; index<alignedSize ; index+=packetSize)
-        {
-          const int row = Derived::RowsAtCompileTime==1 ? 0 : index;
-          const int col = Derived::RowsAtCompileTime==1 ? index : 0;
+        row = rowMajor ? index/innerSize : index%innerSize;
+        col = rowMajor ? index%innerSize : index/innerSize;
+        int start = rowMajor ? col : row;
+        int end = std::min(innerSize, start+alignedSize-index);
+        if (end<start) getchar();
+        for ( ; (rowMajor ? col : row)<end; (rowMajor ? col : row)+=packetSize)
           packet_res = ei_padd(packet_res, mat.template packet<Aligned>(row, col));
-        }
-      }
-      else
-      {
-        for(index = packetSize; index<alignedSize ; index+=packetSize)
-        {
-          // FIXME the following is not really efficient
-          const int row = rowMajor ? index/innerSize : index%innerSize;
-          const int col = rowMajor ? index%innerSize : index/innerSize;
-          packet_res = ei_padd(packet_res, mat.template packet<Aligned>(row, col));
-        }
+        index += (rowMajor ? col : row) - start;
       }
       res = ei_predux(packet_res);
-    asm("#end");
 
       // now we must do the rest without vectorization.
       if(alignedSize == size) return res;