KokkosBlas::gemm

Defined in header: KokkosBlas2_gemm.hpp

template <class execution_space, class AViewType, class BViewType, class CViewType>
void gemm(const execution_space& space, const char transA[], const char transB[],
          typename AViewType::const_value_type& alpha, const AViewType& A, const BViewType& B,
          typename CViewType::const_value_type& beta, const CViewType& C);

template <class AViewType, class BViewType, class CViewType>
void gemm(const char transA[], const char transB[], typename AViewType::const_value_type& alpha, const AViewType& A,
          const BViewType& B, typename CViewType::const_value_type& beta, const CViewType& C);

Perform a dense matrix-matrix multiplication

\[C = \beta * C + \alpha * A * B\]

  1. Iterate over the entries of C, scale them with beta, compute the corresponding dot product of a row of A with a column of B, scale the result with alpha and accumulate back into C using the resources from the space instance, or

  2. Iterate over the entries of C, scale them with beta, compute the corresponding dot product of a row of A with a column of B, scale the result with alpha and accumulate back into C using resources from the default instance of typename CViewType::execution_space.

The function will throw a runtime exception if any of the following conditions are not met:

  • transA stores a valid control value, see below.

  • transB stores a valid control value, see below.

  • A.extent(1) == B.extent(0) && A.extent(0) == C.extent(0) && B.extent(1) == C.extent(1)

Parameters

space:

execution space instance.

transA, transB:

control parameters to apply transformations to A and B respectively, the accepted values are “N” for no transpose, “T” for transpose and “C” for conjugate transpose, all characters after the first one are ignored.

alpha, beta:

scaling parameters for A*B and C, respectively.

A, B, C:

the two matrices to multiply and the matrix where the scaled multiplication values will be accumulated.

Type Requirements

  • execution_space must be a Kokkos execution space

  • AViewType must be a Kokkos View of rank 2 that satisfies

    • Kokkos::SpaceAccessibility<execution_space, typename AViewType::memory_space>::accessible

  • BViewType must be a Kokkos View of rank 2 that satisfies

    • Kokkos::SpaceAccessibility<execution_space, typename BViewType::memory_space>::accessible

  • CViewType must be a Kokkos View of rank 2 that satisfies

    • Kokkos::SpaceAccessibility<execution_space, typename CViewType::memory_space>::accessible

Example

#include<Kokkos_Core.hpp>
#include<KokkosBlas3_gemm.hpp>

int main(int argc, char* argv[]) {
  Kokkos::initialize();
  {
    int M = atoi(argv[1]);
    int N = atoi(argv[2]);

    Kokkos::View<double**> A("A",M,N);
    Kokkos::View<double**> B("B",N,M);
    Kokkos::View<double**> C("C",M,M);

    Kokkos::deep_copy(A,1.0);
    Kokkos::deep_copy(B,2.0);

    const double alpha = double(1.0);
    const double beta = double(0.0);

    KokkosBlas::gemm("N","N",alpha,A,B,beta,C);
  }
  Kokkos::finalize();
}