[SYCL][CUDA] Matrix MMA for double type using nvptx.

SYCL/Matrix/joint_matrix_tensorcore_double.cpp

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+// REQUIRES: gpu, cuda
+
+// RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple -Xsycl-target-backend --cuda-gpu-arch=sm_80 -DSYCL_EXT_ONEAPI_MATRIX=3  %s -o %t.out
+//
+// Specifying the sm version via the --cuda-gpu-arch flag is necessary
+// for the Nvidia case.  DPC++ JIT compilation is not
+// supported for the Nvidia case, although some JIT optimizations are performed
+// at the level of the PTX assembly code.
+
+#include <CL/sycl.hpp>
+
+using namespace sycl;
+using namespace sycl::ext::oneapi::experimental::matrix;
+
+// Example usage of Nvidia matrix multiply.
+// Optimizations such as memory paddings for avoiding bank conflicts are not
+// included in this test which aids clarity for what is going on. This example
+// forms a "Big matrix" corresponding to a single "TILE" using cuda example
+// terminology.  Multiple TILES can be used to construct yet larger matrices.
+// This example uses row_major a, b, and accumulator matrices.
+
+// M, N, K define the unit sizes of dimensions of the three types (a, b,
+// accumulator) of matrices per subgroup operation.
+constexpr int M = 8; // number of rows of "C"/"D" (Accumulator) sub-matrices,
+                     // number of cols of "B" sub-matrix.
+constexpr int N = 8; // number of cols of "C"/"D" (Accumulator) sub-matrices,
+                     // number of rows of "A" sub-matrix.
+constexpr int K =
+    4; // number of cols of "A"/number of rows of "B" sub-matrices.
+
+constexpr int N_THREADS_PER_MATRIX_OP =
+    32; // the number of threads per MMA subgroup is always 32 for Nvidia.
+
+constexpr int SUB_TILES_M =
+    77; // number of submatrices per row of accumulator ("C", "D") matrices.
+constexpr int SUB_TILES_N =
+    55; // number of submatrices per col of accumulator matrices.
+constexpr int SUB_TILES_K =
+    257; // number of submatrices per col of "A"/per row of "B", matrices.
+
+constexpr int BIG_M =
+    SUB_TILES_M *
+    M; // total number of M dimension matrix elements for the "Big matrix".
+constexpr int BIG_N =
+    SUB_TILES_N *
+    N; // total number of N dimension matrix elements for the "Big matrix".
+constexpr int BIG_K =
+    SUB_TILES_K *
+    K; // total number of K dimension matrix elements for the "Big matrix".
+
+// The stride should equal the number of elements between consecutive leading
+// dimensions of the "Big matrix". e.g. number of elements per row if matrix is
+// indexed row major. The stride tells the implementation how many elements to
+// skip in memory matrix row/column multiplications.
+constexpr int STRIDE_A = BIG_K; // row major. If col major should equal BIG_M.
+constexpr int STRIDE_B = BIG_N; // row_major. If col major should equal BIG_K.
+constexpr int STRIDE_C = BIG_N; // row major. If col major should equal BIG_M.
+
+double A[BIG_M * BIG_K];
+double B[BIG_K * BIG_N];
+double C[BIG_M * BIG_N];
+double D[BIG_M * BIG_N];
+
+// returns correct (m,n) element of matrix D = A*B + C (assuming all matrices
+// are indexed row_major).
+double matrix_ref_mn(const int &m, const int &n) {
+  double res = C[m * BIG_N + n];
+
+  for (int k = 0; k < BIG_K; k++)
+    res += A[m * BIG_K + k] * B[k * BIG_N + n];
+  return res;
+}
+
+int main() {
+  for (int i = 0; i < BIG_M * BIG_N; i++) {
+    C[i] = i;
+    D[i] = 0;
+  }
+
+  for (int i = 0; i < BIG_M * BIG_K; i++) {
+    A[i] = i;
+  }
+
+  for (int i = 0; i < BIG_K * BIG_N; i++) {
+    B[i] = i;
+  }
+
+  buffer<double, 1> bufA(A, range<1>(BIG_M * BIG_K));
+  buffer<double, 1> bufB(B, range<1>(BIG_K * BIG_N));
+  buffer<double, 1> bufC(C, range<1>(BIG_M * BIG_N));
+  buffer<double, 1> bufD(D, range<1>(BIG_M * BIG_N));
+
+  queue q;
+  q.submit([&](handler &cgh) {
+    auto accC = bufC.get_access<access::mode::read_write>(cgh);
+    auto accA = bufA.get_access<access::mode::read_write>(cgh);
+    auto accB = bufB.get_access<access::mode::read_write>(cgh);
+    auto accD = bufD.get_access<access::mode::read_write>(cgh);
+
+    range<2> LocalRange = {1, N_THREADS_PER_MATRIX_OP};
+    range<2> GlobalRange = {SUB_TILES_M, SUB_TILES_N * N_THREADS_PER_MATRIX_OP};
+
+    cgh.parallel_for<class imatrix>(
+        nd_range<2>(GlobalRange, LocalRange), [=
+    ](nd_item<2> item) [[sycl::reqd_work_group_size(1, 1, 32)]] {
+          sycl::sub_group sg = item.get_sub_group();
+
+          const auto m =
+              item.get_group()
+                  .get_id()[0]; // row id of current submatrix of BIG C matrix
+          const auto n =
+              item.get_group().get_id()[1]; // column id of current submatrix of
+                                            // BIG C matrix
+
+          joint_matrix<double, matrix_use::accumulator, M, N,
+                       matrix_layout::row_major>
+              sub_c;
+
+          joint_matrix<double, matrix_use::a, M, K, matrix_layout::row_major>
+              sub_a;
+
+          joint_matrix<double, matrix_use::b, K, N, matrix_layout::row_major>
+              sub_b;
+
+          joint_matrix_load(sg, sub_c,
+                            accC.get_pointer() + (m * M) * BIG_N + n * N,
+                            STRIDE_C);
+
+          for (int k = 0; k < SUB_TILES_K;
+               k += 1) // row/col id of current submatrix of BIG A/B matrices
+          {
+            joint_matrix_load(sg, sub_a,
+                              accA.get_pointer() + (k * K) + (m * M * BIG_K),
+                              STRIDE_A);
+
+            joint_matrix_load(sg, sub_b,
+                              accB.get_pointer() + (k * K * BIG_N) + (n * N),
+                              STRIDE_B);
+
+            sub_c = joint_matrix_mad(sg, sub_a, sub_b, sub_c);
+          }
+          joint_matrix_store(sg, sub_c,
+                             accD.get_pointer() + (m * M) * BIG_N + n * N,
+                             STRIDE_C);
+        });
+  });
+
+  const auto host_accessor = bufD.get_access<cl::sycl::access::mode::read>();
+
+  for (int m = 0; m < BIG_M; m++)
+    for (int n = 0; n < BIG_N; n++) {
+      assert(host_accessor[m * BIG_N + n] == matrix_ref_mn(m, n));
+    }
+
+  return 0;
+};