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program example_sparse_data_accessors
use stdlib_linalg_constants, only: dp
use stdlib_sparse
implicit none
real(dp) :: mat(2, 2)
real(dp), allocatable :: dense_matrix(:, :)
type(CSR_dp_type) :: CSR
type(COO_dp_type) :: COO
integer :: i, j, locdof(2)
! Initial data
mat(:, 1) = [1._dp, 2._dp]
mat(:, 2) = [2._dp, 1._dp]
allocate (dense_matrix(5, 5), source=0._dp)
do i = 0, 3
dense_matrix(1 + i:2 + i, 1 + i:2 + i) = dense_matrix(1 + i:2 + i, 1 + i:2 + i) + mat
end do
print *, 'Original Matrix'
do j = 1, 5
print '(5f8.1)', dense_matrix(j, :)
end do
! Initialize CSR data and reset dense reference matrix
call dense2coo(dense_matrix, COO)
call coo2csr(COO, CSR)
CSR%data = 0._dp
dense_matrix = 0._dp
! Iteratively add blocks of data
do i = 0, 3
locdof(1:2) = [1 + i, 2 + i]
call CSR%add(locdof, locdof, mat)
! lets print a dense view of every step
call csr2dense(CSR, dense_matrix)
print '(A,I2)', 'Add block :', i + 1
do j = 1, 5
print '(5f8.1)', dense_matrix(j, :)
end do
end do
! Request values from the matrix
print *, ''
print *, 'within sparse pattern :', CSR%at(2, 1)
print *, 'outside sparse pattern :', CSR%at(5, 2)
print *, 'outside matrix pattern :', CSR%at(7, 7)
end program example_sparse_data_accessors
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