program RestoreCSRdata
implicit none
integer, parameter :: n = 5
integer :: i, j, k, mm, tmp, fileid, first, num
real(kind=8) :: matrix(n,n), x(n), a(n,n)
real(kind=8), allocatable :: aa(:)
integer, allocatable :: ia(:), ja(:)
type :: node
real(kind=8) :: s
integer :: k1, k2
type (node), pointer :: next
end type node
type (node), pointer :: head, tail, p, q
!// input data
open ( newunit = fileid, file = 'SparseMatrix.txt' ) !// The sparse matrix data needs to be given by itself
do i = 1, n
read ( fileid,* ) matrix(i,:)
end do
close ( fileid )
!// =========================store data by CSR format=======================
first = 1
if ( .not.associated(p) ) then
allocate( p )
q => p
nullify( p%next )
q%k2 = first
tmp = q%k2
end if
num = 0 !// calculate the number of no-zero
do i = 1, n
mm = 0 !// calculate the position of no-zero in every row
do j = i, n
if ( matrix(i,j) /= 0.0 ) then
if ( .not.associated(head) ) then
allocate( head )
tail => head
nullify( tail%next )
tail%s = matrix(i,j)
tail%k1 = j
num = num + 1
mm = mm + 1
else
allocate( tail%next )
tail => tail%next
tail%s = matrix(i,j)
tail%k1 = j
num = num + 1
mm = mm + 1
nullify( tail%next )
end if
end if
end do
if ( associated(p) ) then
allocate( q%next )
q => q%next
q%k2 = tmp + mm
tmp = q%k2
nullify( q%next )
end if
end do
allocate( aa(num), ja(num), ia(n+1) ) !// store the no-zero element
!// output a and ja
tail => head
j = 1
do
if ( .not.associated(tail) ) exit
aa(j) = tail%s
ja(j) = tail%k1
j = j + 1
tail => tail%next
end do
!// output ia
q => p
j = 1
do
if ( .not.associated(q) ) exit
ia(j) = q%k2
j = j + 1
q => q%next
end do
nullify( head, tail, p, q )
!// =========================store data by CSR format=======================
write ( *,'(a)' ) '>> Original data'
write ( *,'(5f7.2)' ) matrix
write ( *,'(a)' ) '>> CSR data'
write ( *,'(*(f7.2))' ) aa
write ( *,'(a)' ) '>> Colnum of CSR data'
write ( *,'(*(i4))' ) ja
write ( *,'(a)' ) '>> The position of CSR data'
write ( *,'(*(i4))' ) ia
!// Restore the original array
a = 0.d0
j = 0
do i = 1, n
num = ia(i+1) - ia(i)
do k = j+1, j+num
a(i,ja(k)) = aa(k)
a(ja(k),i) = aa(k)
end do
j = j + num
end do
deallocate( aa, ja, ia )
write ( *,'(a)' ) '>> Restore the original array'
do i = 1, n
write(*,'(*(f7.2))') a(i,:)
end do
end program RestoreCSRdata
運行結果如下：
>> Original data
1.00 0.00 0.00 2.00 0.00
0.00 4.00 0.00 5.00 0.00
0.00 0.00 7.00 8.00 9.00
2.00 5.00 8.00 11.00 0.00
0.00 0.00 9.00 0.00 12.00
>> CSR data
1.00 2.00 4.00 5.00 7.00 8.00 9.00 11.00 12.00
>> Colnum of CSR data
1 4 2 4 3 4 5 4 5
>> The position of CSR data
1 3 5 8 9 10
>> Restore the original array
1.00 0.00 0.00 2.00 0.00
0.00 4.00 0.00 5.00 0.00
0.00 0.00 7.00 8.00 9.00
2.00 5.00 8.00 11.00 0.00
0.00 0.00 9.00 0.00 12.00
請按任意鍵繼續. . .
