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program example_solve_pcg
use stdlib_kinds, only: int8, dp
use stdlib_sparse
use stdlib_linalg_iterative_solvers, only: stdlib_solve_pcg
type(CSR_dp_type) :: laplacian_csr
type(COO_dp_type) :: COO
real(dp) :: laplacian(5,5)
real(dp) :: x(5), rhs(5)
logical(int8) :: dirichlet(5)
laplacian = reshape( [1, -1, 0, 0, 0,&
-1, 2, -1, 0, 0,&
0, -1, 2, -1, 0,&
0, 0, -1, 2, -1,&
0, 0, 0, -1, 1] , [5,5])
call dense2coo(laplacian,COO)
call coo2csr(COO,laplacian_csr)
x = 0._dp
rhs = real( [0,0,5,0,0], kind=dp )
dirichlet = .false._int8
dirichlet([1,5]) = .true._int8
call stdlib_solve_pcg(laplacian, rhs, x, rtol=1.d-6, di=dirichlet)
print *, x !> solution: [0.0, 2.5, 5.0, 2.5, 0.0]
x = 0._dp
call stdlib_solve_pcg(laplacian_csr, rhs, x, rtol=1.d-6, di=dirichlet)
print *, x !> solution: [0.0, 2.5, 5.0, 2.5, 0.0]
end program
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