From 6e40454a6e6cc57c07c7340148657c985ca6c928 Mon Sep 17 00:00:00 2001
From: Eugene Zhulenev <ezhulenev@google.com>
Date: Wed, 2 Oct 2019 11:06:02 -0700
Subject: Add beta to TensorContractionKernel and make memset optional

---
 .../CXX11/src/Tensor/TensorContractionThreadPool.h | 29 ++++++++++++++--------
 1 file changed, 18 insertions(+), 11 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 873db5efd..26c9fac17 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorContractionThreadPool.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorContractionThreadPool.h
@@ -904,14 +904,16 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
 
       const Index nend = n * gn_ + gn(n);
       for (Index n1 = n * gn_; n1 < nend; n1++) {
-        if (k == 0) {
-          // Zero the output memory in parallel.
-          // On 10000x2x10000 mm zeroing can easily take half of time.
-          // Zero (bn x m) row. Safe to do here because all kernels that will
-          // write to this memory depend on completion of this task.
-          // Note: don't call device_.memset() here. device_.memset() blocks on
-          // thread pool worker thread, which can lead to underutilization and
-          // deadlocks.
+        if (!TensorContractionKernel::HasBeta && k == 0) {
+          // Zero the output memory in parallel, only if contraction kernel does
+          // not support `beta`. Otherwise we will pass beta 0.0 to the first
+          // call to the `TensorContractionKernel::invoke()`.
+          //
+          // On 10000x2x10000 mm zeroing can easily take half of time. Zero (bn
+          // x m) row. Safe to do here because all kernels that will write to
+          // this memory depend on completion of this task. Note: don't call
+          // device_.memset() here. device_.memset() blocks on thread pool
+          // worker thread, which can lead to underutilization and deadlocks.
           memset(buffer_ + n1 * bn_ * m_, 0, bn(n1) * m_ * sizeof(Scalar));
         }
         kernel_.packRhs(&packed_rhs(n, k, n1, use_thread_local),
@@ -936,6 +938,12 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
       // (rhs fits into L2$ while lhs only into L3$).
       const Index nend = n * gn_ + gn(n);
       const Index mend = m * gm_ + gm(m);
+
+      // NOTE: output = alpha * LHS * RHS + beta * output.
+      const Scalar alpha = Scalar(1);
+      const Scalar beta =
+          (TensorContractionKernel::HasBeta && k == 0) ? Scalar(0) : Scalar(1);
+
       if (shard_by_col_) {
         for (Index n1 = n * gn_; n1 < nend; n1++) {
           for (Index m1 = m * gm_; m1 < mend; m1++) {
@@ -944,7 +952,7 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
                 output_mapper,
                 packed_lhs(m, k, m1, !shard_by_col_ && use_thread_local),
                 packed_rhs(n, k, n1, shard_by_col_ && use_thread_local), bm(m1),
-                bk(k), bn(n1), Scalar(1));
+                bk(k), bn(n1), alpha, beta);
 
             // We are done with the last task for the [m1, n1] block.
             if (k + 1 == nk_) {
@@ -961,7 +969,7 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
                 output_mapper,
                 packed_lhs(m, k, m1, !shard_by_col_ && use_thread_local),
                 packed_rhs(n, k, n1, shard_by_col_ && use_thread_local), bm(m1),
-                bk(k), bn(n1), Scalar(1));
+                bk(k), bn(n1), alpha, beta);
 
             // We are done with the last task for the [m1, n1] block.
             if (k + 1 == nk_) {
@@ -1266,7 +1274,6 @@ struct TensorEvaluator<const TensorContractionOp<Indices, LeftArgType, RightArgT
     template <int Alignment>
     void processBlock(Index block_idx, Index begin, Index end) {
       Scalar* buf = block_buffers[block_idx];
-      ::memset(buf, 0, buffer_size_bytes);
 
       TENSOR_CONTRACTION_DISPATCH(
           evaluator->template evalGemmPartialWithoutOutputKernel, Alignment,
-- 
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