KokkosBlas::syr2

Defined in header: KokkosBlas2_syr2.hpp

template <class ExecutionSpace, class XViewType, class YViewType, class AViewType>
void syr2(const ExecutionSpace& space, const char trans[], const char uplo[],
          const typename AViewType::const_value_type& alpha, const XViewType& x,
          const YViewType& y, const AViewType& A)

template <class XViewType, class YViewType, class AViewType>
void syr2(const char trans[], const char uplo[],
          const typename AViewType::const_value_type& alpha, const XViewType& x,
          const YViewType& y, const AViewType& A)

Perform a symmetric rank-2 update of matrix A by vectors x and y with scaling factor alpha,

\[A = A + \alpha (x * y^T + y * x^T).\]

  1. Iterate of the entries of A and update them with the alpha scaled and symmetrized product of the entries of x and y^T using resources from the space instance.

  2. Iterate of the entries of A and update them with the alpha scaled and symmetrized product of the entries of x and y^T using resources from the default instance of typename AViewType::execution_space.

The function will throw a runtime exception if A.extent(0) != X.extent(0) || A.extent(1) != X.extent(0) || A.extent(0) != Y.extent(0) || A.extent(1) != Y.extent(0).

Parameters

space:

execution space instance.

trans:

“T” for transpose and “H” for conjugate transpose of x and y, all characters after the first one are ignored.

alpha:

scaling parameter for the rank update.

x, y:

vectors used to perform the symmetric rank update.

A:

matrix being updated.

Type Requirements

  • execution_space must be a Kokkos execution space

  • XViewType must be a Kokkos View of rank 1 that satisfies

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

  • YViewType must be a Kokkos View of rank 1 that satisfies

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

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

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

    • std::is_same_v<typename AViewType::value_type, typename AViewType::non_const_value_type>

Example

#include <Kokkos_Core.hpp>
#include <KokkosBlas2_syr2.hpp>

int main(int argc, char* argv[]) {
  Kokkos::initialize(argc, argv);
  {
    constexpr int M = 5;

    Kokkos::View<double**> A("A", M, M);
    Kokkos::View<double*> x("X", M);
    Kokkos::View<double*> y("Y", M);

    Kokkos::deep_copy(A, 1.0);
    Kokkos::deep_copy(x, 3.0);
    Kokkos::deep_copy(y, 1.3);

    const double alpha = double(1.0);

    KokkosBlas::syr2("T", "U", alpha, x, y, A);
  }
  Kokkos::finalize();
}