program DG_flow
use f90_kind
use petsc_stuff
implicit none

integer :: row,col,no_rows,no_cols
real(dp) :: mat_entry

type(petsc_matrix_type) :: A_petsc_wrapper
type(petsc_matrix_type) :: B_petsc_wrapper
type(petsc_matrix_type) :: C_petsc_wrapper

! Initialize Petsc

call init_petsc

! Build the A and B matrices (just simple example)

no_rows = 10
no_cols = 10

call init_petsc_matrix(A_petsc_wrapper,no_rows,no_cols,no_cols)
call init_petsc_matrix(B_petsc_wrapper,no_rows,no_cols,no_cols)

do row=1,no_rows
  mat_entry = 1.d0
  call addcoef_petsc_matrix(A_petsc_wrapper%A_PetSC,row,row,mat_entry)
  call addcoef_petsc_matrix(B_petsc_wrapper%A_PetSC,row,row,mat_entry)
enddo

! Finalize the A and B matrices

call finalize_petsc_matrix(A_petsc_wrapper)
call finalize_petsc_matrix(B_petsc_wrapper)

! Fail 1: print some info of the matrix A

call get_info(A_petsc_wrapper)

! Fail 2: Construct matrix C = A * B

call mat_prod(A_petsc_wrapper%A_PetSC,B_petsc_wrapper%A_PetSC,C_petsc_wrapper%A_PetSC)

! Stop Petsc

call stop_petsc

end program DG_flow

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