A sparse array in Fortran can be implemented using a combination of arrays and linked lists. Each element in the sparse array can be represented by a node in a linked list, and the array itself can be an array of pointers to these nodes.
Here is an example implementation:
type sparse_node
integer :: value
integer :: row, col
type(sparse_node), pointer :: next_row, next_col
end type
type(sparse_node), pointer :: row_start(:), col_start(:)
integer :: max_rows, max_cols
! Initialize the linked lists
allocate(row_start(max_rows), col_start(max_cols))
do i = 1, max_rows
row_start(i) => null()
enddo
do j = 1, max_cols
col_start(j) => null()
enddo
! Insert a value into the sparse array at position (i, j)
subroutine insert_sparse(i, j, value)
type(sparse_node), pointer :: node
allocate(node)
node%value = value
node%row = i
node%col = j
node%next_row => row_start(i)
row_start(i) => node
node%next_col => col_start(j)
col_start(j) => node
end subroutine
! Get a value from the sparse array at position (i, j)
function get_sparse(i, j) result(value)
integer :: i, j
type(sparse_node), pointer :: node
value = 0
node => row_start(i)
do while (associated(node))
if (node%col == j) then
value = node%value
exit
endif
node => node%next_row
enddo
end function
In this implementation, max_rows
and max_cols
are the maximum dimensions of the array, and insert_sparse
inserts a value into the sparse array at position (i, j)
. get_sparse
retrieves a value from the array at position (i, j)
. The row_start
and col_start
arrays hold pointers to the first node in each row and column, respectively.
Asked: 2023-07-03 02:09:16 +0000
Seen: 8 times
Last updated: Jul 03 '23