xref: /libCEED/examples/mfem/bp3.h (revision d4cc18453651bd0f94c1a2e078b2646a92dafdcc)

// Copyright (c) 2017-2026, Lawrence Livermore National Security, LLC and other CEED contributors.
// All Rights Reserved. See the top-level LICENSE and NOTICE files for details.
//
// SPDX-License-Identifier: BSD-2-Clause
//
// This file is part of CEED:  http://github.com/ceed

#include <ceed/types.h>

/// A structure used to pass additional data to f_build_diff and f_apply_diff
struct BuildContext {
  CeedInt dim, space_dim;
};

/// libCEED Q-function for building quadrature data for a diffusion operator
CEED_QFUNCTION(f_build_diff)(void *ctx, const CeedInt Q, const CeedScalar *const *in, CeedScalar *const *out) {
  BuildContext *bc = (BuildContext *)ctx;
  // in[0] is Jacobians with shape [dim, nc=dim, Q]
  // in[1] is quadrature weights, size (Q)
  //
  // At every quadrature point, compute w/det(J).adj(J).adj(J)^T and store the symmetric part of the result.
  const CeedScalar *J = in[0], *w = in[1];
  CeedScalar       *qdata = out[0];

  switch (bc->dim + 10 * bc->space_dim) {
    case 11:
      // Quadrature Point Loop
      CeedPragmaSIMD for (CeedInt i = 0; i < Q; i++) { qdata[i] = w[i] / J[i]; }
      break;
    case 22:
      // Quadrature Point Loop
      CeedPragmaSIMD for (CeedInt i = 0; i < Q; i++) {
        // J: 0 2   qdata: 0 2   adj(J):  J22 -J12
        //    1 3          2 1           -J21  J11
        const CeedScalar J11 = J[i + Q * 0];
        const CeedScalar J21 = J[i + Q * 1];
        const CeedScalar J12 = J[i + Q * 2];
        const CeedScalar J22 = J[i + Q * 3];
        const CeedScalar qw  = w[i] / (J11 * J22 - J21 * J12);
        qdata[i + Q * 0]     = qw * (J12 * J12 + J22 * J22);
        qdata[i + Q * 1]     = qw * (J11 * J11 + J21 * J21);
        qdata[i + Q * 2]     = -qw * (J11 * J12 + J21 * J22);
      }
      break;
    case 33:
      // Quadrature Point Loop
      CeedPragmaSIMD for (CeedInt i = 0; i < Q; i++) {
        // J: 0 3 6   qdata: 0 5 4
        //    1 4 7          5 1 3
        //    2 5 8          4 3 2
        const CeedScalar J11 = J[i + Q * 0];
        const CeedScalar J21 = J[i + Q * 1];
        const CeedScalar J31 = J[i + Q * 2];
        const CeedScalar J12 = J[i + Q * 3];
        const CeedScalar J22 = J[i + Q * 4];
        const CeedScalar J32 = J[i + Q * 5];
        const CeedScalar J13 = J[i + Q * 6];
        const CeedScalar J23 = J[i + Q * 7];
        const CeedScalar J33 = J[i + Q * 8];
        const CeedScalar A11 = J22 * J33 - J23 * J32;
        const CeedScalar A12 = J13 * J32 - J12 * J33;
        const CeedScalar A13 = J12 * J23 - J13 * J22;
        const CeedScalar A21 = J23 * J31 - J21 * J33;
        const CeedScalar A22 = J11 * J33 - J13 * J31;
        const CeedScalar A23 = J13 * J21 - J11 * J23;
        const CeedScalar A31 = J21 * J32 - J22 * J31;
        const CeedScalar A32 = J12 * J31 - J11 * J32;
        const CeedScalar A33 = J11 * J22 - J12 * J21;
        const CeedScalar qw  = w[i] / (J11 * A11 + J21 * A12 + J31 * A13);
        qdata[i + Q * 0]     = qw * (A11 * A11 + A12 * A12 + A13 * A13);
        qdata[i + Q * 1]     = qw * (A21 * A21 + A22 * A22 + A23 * A23);
        qdata[i + Q * 2]     = qw * (A31 * A31 + A32 * A32 + A33 * A33);
        qdata[i + Q * 3]     = qw * (A21 * A31 + A22 * A32 + A23 * A33);
        qdata[i + Q * 4]     = qw * (A11 * A31 + A12 * A32 + A13 * A33);
        qdata[i + Q * 5]     = qw * (A11 * A21 + A12 * A22 + A13 * A23);
      }
      break;
  }
  return 0;
}

/// libCEED Q-function for applying a diff operator
CEED_QFUNCTION(f_apply_diff)(void *ctx, const CeedInt Q, const CeedScalar *const *in, CeedScalar *const *out) {
  BuildContext *bc = (BuildContext *)ctx;
  // in[0], out[0] have shape [dim, nc=1, Q]
  const CeedScalar *ug = in[0], *qdata = in[1];
  CeedScalar       *vg = out[0];

  switch (bc->dim) {
    case 1:
      // Quadrature Point Loop
      CeedPragmaSIMD for (CeedInt i = 0; i < Q; i++) { vg[i] = ug[i] * qdata[i]; }
      break;
    case 2:
      // Quadrature Point Loop
      CeedPragmaSIMD for (CeedInt i = 0; i < Q; i++) {
        const CeedScalar ug0 = ug[i + Q * 0];
        const CeedScalar ug1 = ug[i + Q * 1];
        vg[i + Q * 0]        = qdata[i + Q * 0] * ug0 + qdata[i + Q * 2] * ug1;
        vg[i + Q * 1]        = qdata[i + Q * 2] * ug0 + qdata[i + Q * 1] * ug1;
      }
      break;
    case 3:
      // Quadrature Point Loop
      CeedPragmaSIMD for (CeedInt i = 0; i < Q; i++) {
        const CeedScalar ug0 = ug[i + Q * 0];
        const CeedScalar ug1 = ug[i + Q * 1];
        const CeedScalar ug2 = ug[i + Q * 2];
        vg[i + Q * 0]        = qdata[i + Q * 0] * ug0 + qdata[i + Q * 5] * ug1 + qdata[i + Q * 4] * ug2;
        vg[i + Q * 1]        = qdata[i + Q * 5] * ug0 + qdata[i + Q * 1] * ug1 + qdata[i + Q * 3] * ug2;
        vg[i + Q * 2]        = qdata[i + Q * 4] * ug0 + qdata[i + Q * 3] * ug1 + qdata[i + Q * 2] * ug2;
      }
      break;
  }
  return 0;
}