KokkosKernel.h

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//* This file is part of the MOOSE framework
//* https://www.mooseframework.org
//*
//* All rights reserved, see COPYRIGHT for full restrictions
//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
//*
//* Licensed under LGPL 2.1, please see LICENSE for details
//* https://www.gnu.org/licenses/lgpl-2.1.html

#pragma once

#include "KokkosKernelBase.h"

namespace Moose
{
namespace Kokkos
{

class Kernel : public KernelBase
{
public:
  static InputParameters validParams();

  Kernel(const InputParameters & parameters);

  virtual void computeResidual() override;
  virtual void computeJacobian() override;


  KOKKOS_FUNCTION Real computeQpJacobian(const unsigned int /* i */,
                                         const unsigned int /* j */,
                                         const unsigned int /* qp */,
                                         AssemblyDatum & /* datum */) const
  {
    return 0;
  }
  KOKKOS_FUNCTION Real computeQpOffDiagJacobian(const unsigned int /* i */,
                                                const unsigned int /* j */,
                                                const unsigned int /* jvar */,
                                                const unsigned int /* qp */,
                                                AssemblyDatum & /* datum */) const
  {
    return 0;
  }
  static auto defaultJacobian() { return &Kernel::computeQpJacobian; }
  static auto defaultOffDiagJacobian() { return &Kernel::computeQpOffDiagJacobian; }

  template <typename Derived>
  KOKKOS_FUNCTION void operator()(ResidualLoop, const ThreadID tid, const Derived & kernel) const;
  template <typename Derived>
  KOKKOS_FUNCTION void operator()(JacobianLoop, const ThreadID tid, const Derived & kernel) const;
  template <typename Derived>
  KOKKOS_FUNCTION void
  operator()(OffDiagJacobianLoop, const ThreadID tid, const Derived & kernel) const;


  template <typename Derived>
  KOKKOS_FUNCTION void computeResidualInternal(const Derived & kernel, AssemblyDatum & datum) const;
  template <typename Derived>
  KOKKOS_FUNCTION void computeJacobianInternal(const Derived & kernel, AssemblyDatum & datum) const;
  template <typename Derived>
  KOKKOS_FUNCTION void computeOffDiagJacobianInternal(const Derived & kernel,
                                                      AssemblyDatum & datum) const;

protected:
  const VariableTestValue _test;
  const VariableTestGradient _grad_test;
  const VariablePhiValue _phi;
  const VariablePhiGradient _grad_phi;
  const VariableValue _u;
  const VariableGradient _grad_u;
};

template <typename Derived>
KOKKOS_FUNCTION void
Kernel::operator()(ResidualLoop, const ThreadID tid, const Derived & kernel) const
{
  auto elem = kokkosBlockElementID(tid);

  AssemblyDatum datum(elem,
                      libMesh::invalid_uint,
                      kokkosAssembly(),
                      kokkosSystems(),
                      _kokkos_var,
                      _kokkos_var.var());

  kernel.computeResidualInternal(kernel, datum);
}

template <typename Derived>
KOKKOS_FUNCTION void
Kernel::operator()(JacobianLoop, const ThreadID tid, const Derived & kernel) const
{
  auto elem = kokkosBlockElementID(tid);

  AssemblyDatum datum(elem,
                      libMesh::invalid_uint,
                      kokkosAssembly(),
                      kokkosSystems(),
                      _kokkos_var,
                      _kokkos_var.var());

  kernel.computeJacobianInternal(kernel, datum);
}

template <typename Derived>
KOKKOS_FUNCTION void
Kernel::operator()(OffDiagJacobianLoop, const ThreadID tid, const Derived & kernel) const
{
  auto elem = kokkosBlockElementID(_thread(tid, 1));

  auto & sys = kokkosSystem(_kokkos_var.sys());
  auto jvar = sys.getCoupling(_kokkos_var.var())[_thread(tid, 0)];

  if (!sys.isVariableActive(jvar, kokkosMesh().getElementInfo(elem).subdomain))
    return;

  AssemblyDatum datum(
      elem, libMesh::invalid_uint, kokkosAssembly(), kokkosSystems(), _kokkos_var, jvar);

  kernel.computeOffDiagJacobianInternal(kernel, datum);
}

template <typename Derived>
KOKKOS_FUNCTION void
Kernel::computeResidualInternal(const Derived & kernel, AssemblyDatum & datum) const
{
  ResidualObject::computeResidualInternal(
      datum,
      [&](Real * local_re, const unsigned int ib, const unsigned int ie)
      {
        for (unsigned int qp = 0; qp < datum.n_qps(); ++qp)
        {
          datum.reinit();

          for (unsigned int i = ib; i < ie; ++i)
            local_re[i] += datum.JxW(qp) * kernel.computeQpResidual(i, qp, datum);
        }
      });
}

template <typename Derived>
KOKKOS_FUNCTION void
Kernel::computeJacobianInternal(const Derived & kernel, AssemblyDatum & datum) const
{
  ResidualObject::computeJacobianInternal(
      datum,
      [&](Real * local_ke, const unsigned int ijb, const unsigned int ije)
      {
        for (unsigned int qp = 0; qp < datum.n_qps(); ++qp)
        {
          datum.reinit();

          for (unsigned int ij = ijb; ij < ije; ++ij)
          {
            unsigned int i = ij % datum.n_jdofs();
            unsigned int j = ij / datum.n_jdofs();

            local_ke[ij] += datum.JxW(qp) * kernel.computeQpJacobian(i, j, qp, datum);
          }
        }
      });
}

template <typename Derived>
KOKKOS_FUNCTION void
Kernel::computeOffDiagJacobianInternal(const Derived & kernel, AssemblyDatum & datum) const
{
  ResidualObject::computeJacobianInternal(
      datum,
      [&](Real * local_ke, const unsigned int ijb, const unsigned int ije)
      {
        for (unsigned int qp = 0; qp < datum.n_qps(); ++qp)
        {
          datum.reinit();

          for (unsigned int ij = ijb; ij < ije; ++ij)
          {
            unsigned int i = ij % datum.n_jdofs();
            unsigned int j = ij / datum.n_jdofs();

            local_ke[ij] +=
                datum.JxW(qp) * kernel.computeQpOffDiagJacobian(i, j, datum.jvar(), qp, datum);
          }
        }
      });
}

} // namespace Kokkos
} // namespace Moose