1 #include <petscvec_kokkos.hpp> 2 #include <../src/vec/vec/impls/seq/kokkos/veckokkosimpl.hpp> 3 #include <petscdevice.h> 4 #include <../src/ksp/pc/impls/vpbjacobi/vpbjacobi.h> 5 #include <../src/mat/impls/aij/seq/kokkos/aijkok.hpp> // for MatInvertVariableBlockDiagonal_SeqAIJKokkos 6 #include <KokkosBlas2_gemv.hpp> 7 8 /* A class that manages helper arrays assisting parallel PCApply() with Kokkos */ 9 struct PC_VPBJacobi_Kokkos { 10 /* Cache the old sizes to check if we need realloc */ 11 PetscInt n; /* number of rows of the local matrix */ 12 PetscInt nblocks; /* number of point blocks */ 13 PetscInt nsize; /* sum of sizes (elements) of the point blocks */ 14 15 /* Helper arrays that are pre-computed on host and then copied to device. 16 bs: [nblocks+1], "csr" version of bsizes[] 17 bs2: [nblocks+1], "csr" version of squares of bsizes[] 18 blkMap: [n], row i of the local matrix belongs to the blkMap[i]-th block 19 */ 20 PetscIntKokkosDualView bs_dual, bs2_dual, blkMap_dual; 21 PetscScalarKokkosView diag; // buffer to store diagonal blocks 22 PetscScalarKokkosView work; // work buffer, with the same size as diag[] 23 PetscLogDouble setupFlops; 24 25 // clang-format off 26 // n: size of the matrix 27 // nblocks: number of blocks 28 // nsize: sum bsizes[i]^2 for i=0..nblocks 29 // bsizes[nblocks]: sizes of blocks 30 PC_VPBJacobi_Kokkos(PetscInt n, PetscInt nblocks, PetscInt nsize, const PetscInt *bsizes) : 31 n(n), nblocks(nblocks), nsize(nsize), bs_dual(NoInit("bs_dual"), nblocks + 1), 32 bs2_dual(NoInit("bs2_dual"), nblocks + 1), blkMap_dual(NoInit("blkMap_dual"), n), 33 diag(NoInit("diag"), nsize), work(NoInit("work"), nsize) 34 { 35 PetscCallVoid(BuildHelperArrays(bsizes)); 36 } 37 // clang-format on 38 39 private: 40 PetscErrorCode BuildHelperArrays(const PetscInt *bsizes) 41 { 42 PetscInt *bs_h = bs_dual.view_host().data(); 43 PetscInt *bs2_h = bs2_dual.view_host().data(); 44 PetscInt *blkMap_h = blkMap_dual.view_host().data(); 45 46 PetscFunctionBegin; 47 setupFlops = 0.0; 48 bs_h[0] = bs2_h[0] = 0; 49 for (PetscInt i = 0; i < nblocks; i++) { 50 PetscInt m = bsizes[i]; 51 bs_h[i + 1] = bs_h[i] + m; 52 bs2_h[i + 1] = bs2_h[i] + m * m; 53 for (PetscInt j = 0; j < m; j++) blkMap_h[bs_h[i] + j] = i; 54 // m^3/3 FMA for A=LU factorization; m^3 FMA for solving (LU)X=I to get the inverse 55 setupFlops += 8.0 * m * m * m / 3; 56 } 57 58 PetscCallCXX(bs_dual.modify_host()); 59 PetscCallCXX(bs2_dual.modify_host()); 60 PetscCallCXX(blkMap_dual.modify_host()); 61 PetscCallCXX(bs_dual.sync_device()); 62 PetscCallCXX(bs2_dual.sync_device()); 63 PetscCallCXX(blkMap_dual.sync_device()); 64 PetscCall(PetscLogCpuToGpu(sizeof(PetscInt) * (2 * (nblocks + 1) + n))); 65 PetscFunctionReturn(PETSC_SUCCESS); 66 } 67 }; 68 69 template <PetscBool transpose> 70 static PetscErrorCode PCApplyOrTranspose_VPBJacobi_Kokkos(PC pc, Vec x, Vec y) 71 { 72 PC_VPBJacobi *jac = (PC_VPBJacobi *)pc->data; 73 PC_VPBJacobi_Kokkos *pckok = static_cast<PC_VPBJacobi_Kokkos *>(jac->spptr); 74 ConstPetscScalarKokkosView xv; 75 PetscScalarKokkosView yv; 76 PetscScalarKokkosView diag = pckok->diag; 77 PetscIntKokkosView bs = pckok->bs_dual.view_device(); 78 PetscIntKokkosView bs2 = pckok->bs2_dual.view_device(); 79 PetscIntKokkosView blkMap = pckok->blkMap_dual.view_device(); 80 const char *label = transpose ? "PCApplyTranspose_VPBJacobi" : "PCApply_VPBJacobi"; 81 82 PetscFunctionBegin; 83 PetscCall(PetscLogGpuTimeBegin()); 84 VecErrorIfNotKokkos(x); 85 VecErrorIfNotKokkos(y); 86 PetscCall(VecGetKokkosView(x, &xv)); 87 PetscCall(VecGetKokkosViewWrite(y, &yv)); 88 #if 0 // TODO: Why the TeamGemv version is 2x worse than the naive one? 89 PetscCallCXX(Kokkos::parallel_for( 90 label, Kokkos::TeamPolicy<>(jac->nblocks, Kokkos::AUTO()), KOKKOS_LAMBDA(const KokkosTeamMemberType &team) { 91 PetscInt bid = team.league_rank(); // block id 92 PetscInt n = bs(bid + 1) - bs(bid); // size of this block 93 const PetscScalar *bbuf = &diag(bs2(bid)); 94 const PetscScalar *xbuf = &xv(bs(bid)); 95 PetscScalar *ybuf = &yv(bs(bid)); 96 const auto &B = Kokkos::View<const PetscScalar **, Kokkos::LayoutLeft>(bbuf, n, n); // wrap it in a 2D view in column-major order 97 const auto &x1 = ConstPetscScalarKokkosView(xbuf, n); 98 const auto &y1 = PetscScalarKokkosView(ybuf, n); 99 if (transpose) { 100 KokkosBlas::TeamGemv<KokkosTeamMemberType, KokkosBlas::Trans::Transpose>::invoke(team, 1., B, x1, 0., y1); // y1 = 0.0 * y1 + 1.0 * B^T * x1 101 } else { 102 KokkosBlas::TeamGemv<KokkosTeamMemberType, KokkosBlas::Trans::NoTranspose>::invoke(team, 1., B, x1, 0., y1); // y1 = 0.0 * y1 + 1.0 * B * x1 103 } 104 })); 105 #else 106 PetscCallCXX(Kokkos::parallel_for( 107 label, pckok->n, KOKKOS_LAMBDA(PetscInt row) { 108 const PetscScalar *Bp, *xp; 109 PetscScalar *yp; 110 PetscInt i, j, k, m; 111 112 k = blkMap(row); /* k-th block/matrix */ 113 m = bs(k + 1) - bs(k); /* block size of the k-th block */ 114 i = row - bs(k); /* i-th row of the block */ 115 Bp = &diag(bs2(k) + i * (transpose ? m : 1)); /* Bp points to the first entry of i-th row/column */ 116 xp = &xv(bs(k)); 117 yp = &yv(bs(k)); 118 119 yp[i] = 0.0; 120 for (j = 0; j < m; j++) { 121 yp[i] += Bp[0] * xp[j]; 122 Bp += transpose ? 1 : m; 123 } 124 })); 125 #endif 126 PetscCall(VecRestoreKokkosView(x, &xv)); 127 PetscCall(VecRestoreKokkosViewWrite(y, &yv)); 128 PetscCall(PetscLogGpuFlops(pckok->nsize * 2)); /* FMA on entries in all blocks */ 129 PetscCall(PetscLogGpuTimeEnd()); 130 PetscFunctionReturn(PETSC_SUCCESS); 131 } 132 133 static PetscErrorCode PCDestroy_VPBJacobi_Kokkos(PC pc) 134 { 135 PC_VPBJacobi *jac = (PC_VPBJacobi *)pc->data; 136 137 PetscFunctionBegin; 138 PetscCallCXX(delete static_cast<PC_VPBJacobi_Kokkos *>(jac->spptr)); 139 PetscCall(PCDestroy_VPBJacobi(pc)); 140 PetscFunctionReturn(PETSC_SUCCESS); 141 } 142 143 PETSC_INTERN PetscErrorCode PCSetUp_VPBJacobi_Kokkos(PC pc) 144 { 145 PC_VPBJacobi *jac = (PC_VPBJacobi *)pc->data; 146 PC_VPBJacobi_Kokkos *pckok = static_cast<PC_VPBJacobi_Kokkos *>(jac->spptr); 147 PetscInt i, nlocal, nblocks, nsize = 0; 148 const PetscInt *bsizes; 149 150 PetscFunctionBegin; 151 PetscCall(MatGetVariableBlockSizes(pc->pmat, &nblocks, &bsizes)); 152 PetscCall(MatGetLocalSize(pc->pmat, &nlocal, NULL)); 153 PetscCheck(!nlocal || nblocks, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call MatSetVariableBlockSizes() before using PCVPBJACOBI"); 154 155 if (!jac->diag) { 156 PetscInt max_bs = -1, min_bs = PETSC_MAX_INT; 157 for (i = 0; i < nblocks; i++) { 158 min_bs = PetscMin(min_bs, bsizes[i]); 159 max_bs = PetscMax(max_bs, bsizes[i]); 160 nsize += bsizes[i] * bsizes[i]; 161 } 162 jac->nblocks = nblocks; 163 jac->min_bs = min_bs; 164 jac->max_bs = max_bs; 165 } 166 167 // If one calls MatSetVariableBlockSizes() multiple times and sizes have been changed (is it allowed?), we delete the old and rebuild anyway 168 if (pckok && (pckok->n != nlocal || pckok->nblocks != nblocks || pckok->nsize != nsize)) { 169 PetscCallCXX(delete pckok); 170 pckok = nullptr; 171 } 172 173 PetscCall(PetscLogGpuTimeBegin()); 174 if (!pckok) { 175 PetscCallCXX(pckok = new PC_VPBJacobi_Kokkos(nlocal, nblocks, nsize, bsizes)); 176 jac->spptr = pckok; 177 } 178 179 // Extract diagonal blocks from the matrix and compute their inverse 180 const auto &bs = pckok->bs_dual.view_device(); 181 const auto &bs2 = pckok->bs2_dual.view_device(); 182 const auto &blkMap = pckok->blkMap_dual.view_device(); 183 PetscCall(MatInvertVariableBlockDiagonal_SeqAIJKokkos(pc->pmat, bs, bs2, blkMap, pckok->work, pckok->diag)); 184 pc->ops->apply = PCApplyOrTranspose_VPBJacobi_Kokkos<PETSC_FALSE>; 185 pc->ops->applytranspose = PCApplyOrTranspose_VPBJacobi_Kokkos<PETSC_TRUE>; 186 pc->ops->destroy = PCDestroy_VPBJacobi_Kokkos; 187 PetscCall(PetscLogGpuTimeEnd()); 188 PetscCall(PetscLogGpuFlops(pckok->setupFlops)); 189 PetscFunctionReturn(PETSC_SUCCESS); 190 } 191