tensor_ops.H

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#ifndef TENSOR_OPS_H
#define TENSOR_OPS_H
 
#include "AMReX_Gpu.H"
#include "AMReX_REAL.H"
 
using namespace amrex::literals;
 
namespace amr_wind::utils {

template <typename T>
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE T dot_prod(const T* x, const T* y)
{
    static_assert(
        AMREX_SPACEDIM == 3, "Vector ops only defined for AMREX_SPACEDIM == 3");
    return (x[0] * y[0] + x[1] * y[1] + x[2] * y[2]);
}

template <typename T>
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE T vec_mag(const T* x)
{
    return std::sqrt(dot_prod(x, x));
}

template <typename T>
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE void vec_normalize(T* x)
{
    static_assert(
        AMREX_SPACEDIM == 3, "Vector ops only defined for AMREX_SPACEDIM == 3");
    const T inv_mag = 1.0_rt / vec_mag(x);
    x[0] *= inv_mag;
    x[1] *= inv_mag;
    x[2] *= inv_mag;
}
 
template <typename T>
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE T
dot_prod(const T* x, const T* y, const int ndim)
{
    T sum = 0.0_rt;
    for (int i = 0; i < ndim; ++i) {
        sum += x[i] * y[i];
    }
    return sum;
}

template <typename T>
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE void
cross_prod(const T* a, const T* b, T* c)
{
    static_assert(
        AMREX_SPACEDIM == 3, "Vector ops only defined for AMREX_SPACEDIM == 3");
    c[0] = a[1] * b[2] - a[2] * b[1];
    c[1] = a[2] * b[0] - a[0] * b[2];
    c[2] = a[0] * b[1] - a[1] * b[0];
}

template <typename T>
AMREX_GPU_DEVICE AMREX_FORCE_INLINE void transform_vec(
    const amrex::Array2D<T, 0, AMREX_SPACEDIM, 0, AMREX_SPACEDIM>& tmat,
    const T* x,
    T* y)
{
    static_assert(
        AMREX_SPACEDIM == 3, "Vector ops only defined for AMREX_SPACEDIM == 3");
    y[0] = tmat(0, 0) * x[0] + tmat(0, 1) * x[1] + tmat(0, 2) * x[2];
    y[1] = tmat(1, 0) * x[0] + tmat(1, 1) * x[1] + tmat(1, 2) * x[2];
    y[2] = tmat(2, 0) * x[0] + tmat(2, 1) * x[1] + tmat(2, 2) * x[2];
}

template <typename T>
AMREX_GPU_DEVICE AMREX_FORCE_INLINE void inv_transform_vec(
    const amrex::Array2D<T, 0, AMREX_SPACEDIM, 0, AMREX_SPACEDIM>& tmat,
    const T* x,
    T* y)
{
    static_assert(
        AMREX_SPACEDIM == 3, "Vector ops only defined for AMREX_SPACEDIM == 3");
    y[0] = tmat(0, 0) * x[0] + tmat(1, 0) * x[1] + tmat(2, 0) * x[2];
    y[1] = tmat(0, 1) * x[0] + tmat(1, 1) * x[1] + tmat(2, 1) * x[2];
    y[2] = tmat(0, 2) * x[0] + tmat(1, 2) * x[1] + tmat(2, 2) * x[2];
}
 
} // namespace amr_wind::utils
 
#endif /* TENSOR_OPS_H */