Date: 2026-03-01T05:24:44+00:00

Actual source code: ex1f90.F90

      1: ! Example program demonstrating projection between particle and finite element spaces
      2: program DMSwarmTestProjection
      3: #include <petsc/finclude/petscdmplex.h>
      4: #include <petsc/finclude/petscdmswarm.h>
      5: #include <petsc/finclude/petscksp.h>
      6:   use petscdmplex
      7:   use petscdmswarm
      8:   use petscksp
      9:   implicit none

     11:   DM ::          dm, sw
     12:   PetscFE ::     fe
     13:   KSP ::         ksp
     14:   Mat ::         M_p, M
     15:   Vec ::         f, rho, rhs
     16:   PetscInt ::    dim, Nc = 1, degree = 1, timestep = 0
     17:   PetscInt ::    Np = 100, p, field = 0, zero = 0, bs
     18:   PetscReal ::   time = 0.0, norm
     19:   PetscBool ::   removePoints = PETSC_TRUE
     20:   PetscDataType :: dtype
     21:   PetscScalar, pointer :: coords(:)
     22:   PetscScalar, pointer :: wq(:)
     23:   PetscErrorCode :: ierr

     25:   PetscCallA(PetscInitialize(PETSC_NULL_CHARACTER, ierr))
     26:   PetscCallA(DMCreate(PETSC_COMM_WORLD, dm, ierr))
     27:   PetscCallA(DMSetType(dm, DMPLEX, ierr))
     28:   PetscCallA(DMSetFromOptions(dm, ierr))
     29:   PetscCallA(DMGetDimension(dm, dim, ierr))
     30:   PetscCallA(DMViewFromOptions(dm, PETSC_NULL_OBJECT, '-dm_view', ierr))

     32: !     Create finite element space
     33:   PetscCallA(PetscFECreateLagrange(PETSC_COMM_SELF, dim, Nc, PETSC_FALSE, degree, PETSC_DETERMINE, fe, ierr))
     34:   PetscCallA(DMSetField(dm, field, PETSC_NULL_DMLABEL, PetscObjectCast(fe), ierr))
     35:   PetscCallA(DMCreateDS(dm, ierr))
     36:   PetscCallA(PetscFEDestroy(fe, ierr))

     38: !     Create particle swarm
     39:   PetscCallA(DMCreate(PETSC_COMM_WORLD, sw, ierr))
     40:   PetscCallA(DMSetType(sw, DMSWARM, ierr))
     41:   PetscCallA(DMSetDimension(sw, dim, ierr))
     42:   PetscCallA(DMSwarmSetType(sw, DMSWARM_PIC, ierr))
     43:   PetscCallA(DMSwarmSetCellDM(sw, dm, ierr))
     44:   PetscCallA(DMSwarmRegisterPetscDatatypeField(sw, 'w_q', Nc, PETSC_SCALAR, ierr))
     45:   PetscCallA(DMSwarmFinalizeFieldRegister(sw, ierr))
     46:   PetscCallA(DMSwarmSetLocalSizes(sw, Np, zero, ierr))
     47:   PetscCallA(DMSetFromOptions(sw, ierr))
     48:   PetscCallA(DMSwarmGetField(sw, 'w_q', bs, dtype, wq, ierr))
     49:   PetscCallA(DMSwarmGetField(sw, 'DMSwarmPIC_coor', bs, dtype, coords, ierr))
     50:   do p = 1, Np
     51:     coords(p*2 - 1) = -cos(dble(p)/dble(Np + 1)*PETSC_PI)
     52:     coords(p*2 - 0) = sin(dble(p)/dble(Np + 1)*PETSC_PI)
     53:     wq(p) = 1.0
     54:   end do
     55:   PetscCallA(DMSwarmRestoreField(sw, 'DMSwarmPIC_coor', bs, dtype, coords, ierr))
     56:   PetscCallA(DMSwarmRestoreField(sw, 'w_q', bs, dtype, wq, ierr))
     57:   PetscCallA(DMSwarmMigrate(sw, removePoints, ierr))
     58:   PetscCallA(DMSwarmVectorDefineField(sw, 'w_q', ierr))
     59:   PetscCallA(DMViewFromOptions(sw, PETSC_NULL_OBJECT, '-swarm_view', ierr))

     61: !     Project particles to field
     62: !       This gives M f = \int_\Omega \phi f, which looks like a rhs for a PDE
     63:   PetscCallA(DMCreateMassMatrix(sw, dm, M_p, ierr))
     64:   PetscCallA(DMCreateGlobalVector(dm, rho, ierr))
     65:   PetscCallA(DMSwarmCreateGlobalVectorFromField(sw, 'w_q', f, ierr))
     66:   PetscCallA(MatMultTranspose(M_p, f, rho, ierr))

     68: !     Visualize mesh field
     69:   PetscCallA(DMSetOutputSequenceNumber(dm, timestep, time, ierr))
     70:   PetscCallA(PetscObjectViewFromOptions(PetscObjectCast(rho), PETSC_NULL_OBJECT, '-rho_view', ierr))

     72: !     Project field to particles
     73: !       This gives f_p = M_p^+ M f
     74:   PetscCallA(DMCreateMassMatrix(dm, dm, M, ierr))
     75:   PetscCallA(DMCreateGlobalVector(dm, rhs, ierr))
     76:   if (.false.) then
     77:     PetscCallA(MatMult(M, rho, rhs, ierr)) ! this is what you would do for and FE solve
     78:   else
     79:     PetscCallA(VecCopy(rho, rhs, ierr)) ! Identity: M^1 M rho
     80:   end if
     81:   PetscCallA(KSPCreate(PETSC_COMM_WORLD, ksp, ierr))
     82:   PetscCallA(KSPSetOptionsPrefix(ksp, 'ftop_', ierr))
     83:   PetscCallA(KSPSetFromOptions(ksp, ierr))
     84:   PetscCallA(KSPSetOperators(ksp, M_p, M_p, ierr))
     85:   PetscCallA(KSPSolveTranspose(ksp, rhs, f, ierr))
     86:   PetscCallA(KSPDestroy(ksp, ierr))
     87:   PetscCallA(VecDestroy(rhs, ierr))
     88:   PetscCallA(MatDestroy(M_p, ierr))
     89:   PetscCallA(MatDestroy(M, ierr))

     91: !     Visualize particle field
     92:   PetscCallA(DMSetOutputSequenceNumber(sw, timestep, time, ierr))
     93:   PetscCallA(PetscObjectViewFromOptions(PetscObjectCast(f), PETSC_NULL_OBJECT, '-weights_view', ierr))
     94:   PetscCallA(VecNorm(f, NORM_1, norm, ierr))
     95:   print *, 'Total number density = ', norm
     96: !     Cleanup
     97:   PetscCallA(DMSwarmDestroyGlobalVectorFromField(sw, 'w_q', f, ierr))
     98:   PetscCallA(VecDestroy(rho, ierr))
     99:   PetscCallA(DMDestroy(sw, ierr))
    100:   PetscCallA(DMDestroy(dm, ierr))

    102:   PetscCallA(PetscFinalize(ierr))
    103: end program DMSwarmTestProjection

    105: !/*TEST
    106: !  build:
    107: !    requires: defined(PETSC_USING_F90FREEFORM) double !complex
    108: !
    109: !  test:
    110: !    suffix: 0
    111: !    requires: double
    112: !    args: -dm_plex_simplex 0 -dm_plex_box_faces 40,20 -dm_plex_box_lower -2.0,0.0 -dm_plex_box_upper 2.0,2.0 -ftop_ksp_type lsqr -ftop_pc_type none -dm_view -swarm_view
    113: !    filter: grep -v DM_ | grep -v atomic
    114: !    filter_output: grep -v atomic
    115: !
    116: !TEST*/