Enable the case N != ldc in EigenBlasGemm. (#5976)

* Enable the case N != ldc in EigenBlasGemm.

* Use MemoryHandle instead of direct calling of posix_memalign to alloc temporary memory.

* Use Eigen's slice() instead of a temporary memory.

* Add if-else for different cases in EigenBlasGemm (for N ?= ldc).

Author: Xreki

paddle/function/EigenGemm.cpp

@@ -21,7 +21,7 @@ template <class T>
 struct EigenBlasGemm {
   typedef Eigen::TensorMap<Eigen::Tensor<T, 2, Eigen::RowMajor, int>,
                            Eigen::Aligned>
-      Matrix;
+      EigenMatrix;
 
   static void compute(const bool transA,
                       const bool transB,
@@ -56,14 +56,13 @@ struct EigenBlasGemm {
       sizeB[1] = N;
       CHECK_EQ(N, ldb);
     }
-    Eigen::array<int, 2> sizeC;
-    sizeC[0] = M;
-    sizeC[1] = N;
-    CHECK_EQ(N, ldc);
+    Eigen::array<int, 2> sizeC = {{M, ldc}};
+    Eigen::array<int, 2> offsetC = {{0, 0}};
+    Eigen::array<int, 2> extentC = {{M, N}};
 
-    const Matrix a(const_cast<T*>(A), sizeA);
-    const Matrix b(const_cast<T*>(B), sizeB);
-    Matrix c(C, sizeC);
+    const EigenMatrix a(const_cast<T*>(A), sizeA);
+    const EigenMatrix b(const_cast<T*>(B), sizeB);
+    EigenMatrix c(C, sizeC);
 
     typedef typename Eigen::Tensor<T, 2>::DimensionPair DimPair;
     Eigen::array<DimPair, 1> dims;
@@ -72,12 +71,23 @@ struct EigenBlasGemm {
     dims[0].second = transB ? 1 : 0;
 
     Eigen::DefaultDevice device;
-    if (alpha == T(1) && beta == T(0)) {
-      c.device(device) = a.contract(b, dims);
-    } else if (alpha == T(1) && beta == T(1)) {
-      c.device(device) += a.contract(b, dims);
+    if (N == ldc) {
+      if (alpha == T(1) && beta == T(0)) {
+        c.device(device) = a.contract(b, dims);
+      } else if (alpha == T(1) && beta == T(1)) {
+        c.device(device) += a.contract(b, dims);
+      } else {
+        c.device(device) = alpha * a.contract(b, dims) + beta * c;
+      }
     } else {
-      c.device(device) = alpha * a.contract(b, dims) + beta * c;
+      if (alpha == T(1) && beta == T(0)) {
+        c.slice(offsetC, extentC).device(device) = a.contract(b, dims);
+      } else if (alpha == T(1) && beta == T(1)) {
+        c.slice(offsetC, extentC).device(device) += a.contract(b, dims);
+      } else {
+        c.slice(offsetC, extentC).device(device) =
+            alpha * a.contract(b, dims) + beta * c.slice(offsetC, extentC);
+      }
     }
   }
 };