From 01fd4096d395e7b816459f571bf2328c8435cc37 Mon Sep 17 00:00:00 2001
From: Eugene Zhulenev <ezhulenev@google.com>
Date: Tue, 10 Jul 2018 13:16:38 -0700
Subject: Fuse computations into the Tensor contractions using output kernel

---
 .../CXX11/src/Tensor/TensorContractionThreadPool.h | 51 ++++++++++++++++------
 1 file changed, 38 insertions(+), 13 deletions(-)

(limited to 'unsupported/Eigen/CXX11/src/Tensor/TensorContractionThreadPool.h')

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorContractionThreadPool.h b/unsupported/Eigen/CXX11/src/Tensor/TensorContractionThreadPool.h
index 3c007b183..d7536bd6a 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorContractionThreadPool.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorContractionThreadPool.h
@@ -56,16 +56,16 @@ struct packRhsAndKernelArg {
 }  // end namespace internal
 #endif  // EIGEN_USE_SIMPLE_THREAD_POOL
 
-template<typename Indices, typename LeftArgType, typename RightArgType>
-struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgType>, ThreadPoolDevice> :
-    public TensorContractionEvaluatorBase<TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgType>, ThreadPoolDevice> > {
+template<typename Indices, typename LeftArgType, typename RightArgType, typename OutputKernelType>
+struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgType, OutputKernelType>, ThreadPoolDevice> :
+    public TensorContractionEvaluatorBase<TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgType, OutputKernelType>, ThreadPoolDevice> > {
 
   typedef ThreadPoolDevice Device;
 
-  typedef TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgType>, Device> Self;
+  typedef TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgType, OutputKernelType>, Device> Self;
   typedef TensorContractionEvaluatorBase<Self> Base;
 
-  typedef TensorContractionOp<Indices, LeftArgType, RightArgType> XprType;
+  typedef TensorContractionOp<Indices, LeftArgType, RightArgType, OutputKernelType> XprType;
   typedef typename internal::remove_const<typename XprType::Scalar>::type Scalar;
   typedef typename XprType::Index Index;
   typedef typename XprType::CoeffReturnType CoeffReturnType;
@@ -308,7 +308,7 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
                   this->m_k_strides);
 
     Context<LhsPacker, RhsPacker, GebpKernel, LhsMapper, RhsMapper,
-            OutputMapper>(this->m_device, num_threads, lhs, rhs, buffer, m, n,
+            OutputMapper>(this, num_threads, lhs, rhs, buffer, m, n,
                           k, bm, bn, bk, nm, nn, nk, gm, gn, nm0, nn0,
                           shard_by_col, parallel_pack)
         .run();
@@ -319,16 +319,18 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
             typename LhsMapper, typename RhsMapper, typename OutputMapper>
   class Context {
    public:
-    Context(const Device& device, int num_threads, LhsMapper& lhs,
+    Context(const Self* self, int num_threads, LhsMapper& lhs,
             RhsMapper& rhs, Scalar* buffer, Index tm, Index tn, Index tk, Index bm,
             Index bn, Index bk, Index nm, Index nn, Index nk, Index gm,
             Index gn, Index nm0, Index nn0, bool shard_by_col,
             bool parallel_pack)
-        : device_(device),
+        : device_(self->m_device),
           lhs_(lhs),
           rhs_(rhs),
           buffer_(buffer),
           output_(buffer, tm),
+          output_kernel_(self->m_output_kernel),
+          tensor_contraction_params_(self->m_tensor_contraction_params),
           num_threads_(num_threads),
           shard_by_col_(shard_by_col),
           parallel_pack_(parallel_pack),
@@ -420,6 +422,8 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
     RhsMapper& rhs_;
     Scalar* const buffer_;
     OutputMapper output_;
+    OutputKernelType output_kernel_;
+    TensorContractionParams tensor_contraction_params_;
     const int num_threads_;
     const bool shard_by_col_;
     const bool parallel_pack_;
@@ -536,19 +540,32 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
       const Index mend = m * gm_ + gm(m);
       if (shard_by_col_) {
         for (Index n1 = n * gn_; n1 < nend; n1++) {
-          for (Index m1 = m * gm_; m1 < mend; m1++)
-            GebpKernel()(output_.getSubMapper(m1 * bm_, n1 * bn_),
-                         packed_lhs_[k % (P - 1)][m1],
+          for (Index m1 = m * gm_; m1 < mend; m1++) {
+            const auto output_mapper = output_.getSubMapper(m1 * bm_, n1 * bn_);
+            GebpKernel()(output_mapper, packed_lhs_[k % (P - 1)][m1],
                          packed_rhs_[k % (P - 1)][n1], bm(m1), bk(k), bn(n1),
                          Scalar(1), -1, -1, 0, 0);
+
+            // We are done with the last task for the [m1, n1] block.
+            if (k + 1 == nk_) {
+              output_kernel_(output_mapper, tensor_contraction_params_,
+                             m1 * bm_, n1 * bn_, bm(m1), bn(n1));
+            }
+          }
         }
       } else {
         for (Index m1 = m * gm_; m1 < mend; m1++)
           for (Index n1 = n * gn_; n1 < nend; n1++) {
-            GebpKernel()(output_.getSubMapper(m1 * bm_, n1 * bn_),
-                         packed_lhs_[k % (P - 1)][m1],
+            const auto output_mapper = output_.getSubMapper(m1 * bm_, n1 * bn_);
+            GebpKernel()(output_mapper, packed_lhs_[k % (P - 1)][m1],
                          packed_rhs_[k % (P - 1)][n1], bm(m1), bk(k), bn(n1),
                          Scalar(1), -1, -1, 0, 0);
+
+            // We are done with the last task for the [m1, n1] block.
+            if (k + 1 == nk_) {
+              output_kernel_(output_mapper, tensor_contraction_params_,
+                             m1 * bm_, n1 * bn_, bm(m1), bn(n1));
+            }
           }
       }
       signal_kernel(m, n, k + 1, false);
@@ -747,6 +764,10 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
   }
 
 #else  // EIGEN_USE_SIMPLE_THREAD_POOL
+  // TODO(ezhulenev): SimpleThreadPool will be removed in the future, and seems
+  // like it's not worth adding output kernel support here.
+  static_assert(std::is_same<OutputKernelType, const NoOpOutputKernel>::value,
+                "SimpleThreadPool does not support contraction output kernels.");
 
   template <bool lhs_inner_dim_contiguous, bool rhs_inner_dim_contiguous, bool rhs_inner_dim_reordered, int Alignment>
   void evalProduct(Scalar* buffer) const {
@@ -1065,6 +1086,10 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
   }
 
 #if defined(EIGEN_VECTORIZE_AVX) && defined(EIGEN_USE_LIBXSMM)
+  // TODO(ezhulenev): Add support for output kernels and LIBXSMM.
+  static_assert(std::is_same<OutputKernelType, const NoOpOutputKernel>::value,
+                "XSMM does not support contraction output kernels.");
+
   template<int Alignment>
   class ContextXsmm {
    public:
-- 
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