KokkosBlas::axpby

Defined in header: KokkosBlas1_axpby.hpp

template <class execution_space, class AV, class XMV, class BV, class YMV>
void axpby(const execution_space& exec_space, const AV& a, const XMV& X, const BV& b, const YMV& Y) {

template <class AV, class XMV, class BV, class YMV>
void axpby(const AV& a, const XMV& X, const BV& b, const YMV& Y) {

Scale Y by coefficient b and then add entries of X scaled by coefficient a: Y := a*X + b*Y

  1. Compute Y := a*X + b*Y on the provided exec_space.

  2. Compute Y := a*X + b*Y on the default execution space instance of type XMV::execution_space.

a and b may each be any of the following:

  • a scalar value

  • a rank-0 host-accessible Kokkos::View

  • a rank-0 device-accessible Kokkos::View

  • a rank-1 device-accessible Kokkos::View with extent 1 (the coefficient will be applied to all columns)

  • a rank-1 device-accessible Kokkos::View with extent Y.extent(1) (one coefficient per column)

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

  • Y.extent(0) == X.extent(0) && Y.extent(1) == X.extent(1)

If a is a rank-1 View:

  • a.extent(0) == 1 || a.extent(0) == X.extent(1)

If b is a rank-1 View:

  • b.extent(0) == 1 || b.extent(0) == Y.extent(1)

Note: if b is a single coefficient to apply to all columns of Y, and b is zero, then the values of Y on input are treated as zeros. This means that the axpby will overwrite any NaN or infinity values in Y.

Parameters

space:

execution space instance

a:

scaling factor(s) applied to X

X:

input vector or multi-vector

b:

scaling factor(s) applied to Y

Y:

output vector or multi-vector

Type Requirements

  • execution_space must be a Kokkos execution space

  • XMV must be a Kokkos View of rank 1 or 2 that satisfies

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

  • YMV must be a Kokkos View that satisfies

    • YMV::rank == XMV::rank

    • !std::is_const_v<typename YMV::value_type>

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

  • AV must be a scalar or a Kokkos View that satisfies one of the following:

    • AV::rank == 0

    • AV::rank == 1 && Kokkos::SpaceAccessibility<execution_space, typename YMV::memory_space>::accessible

  • BV must be a scalar or a Kokkos View that satisfies one of the following:

    • BV::rank == 0

    • BV::rank == 1 && Kokkos::SpaceAccessibility<execution_space, typename YMV::memory_space>::accessible