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subroutine spt(m, n, nel, it, ptr,
$ A_R, A_I, A_mnel, A_icol,
$ At_R, At_I, At_mnel, At_icol)
*
* PURPOSE T
* transpose a sparse (scilab) matrix : At = A
*
* PARAMETERS
* inputs
* m : number of rows of A
* n : number of columns of A
* nel : integer, number of non-nul elements of A
* it : -1 for a sparse boolean, 0 a sparse real and 1 for a complex sparse
* A_R : double float array (1..nel), values of the non nul elements
* stored row by row with increasing column indices within a row
* A_I : the same for complex values (case it =1)
* A_icol : integer array (1..nel), columns indices : A_icol(k)
* is column indice of the element stored in A_R(k)
* A_mnel : integer array (1..n) A_mnel(i) is the number of non
* nul elements of row i
*
* outputs
* At_R, At_I, At_icol, At_mnel : the same for the transposed matrix
*
* work array : ptr of size n
*
* AUTHOR
* Bruno Pincon
*
implicit none
integer m, n, nel, it, ptr(*)
integer A_icol(nel), A_mnel(m), At_icol(nel), At_mnel(n)
double precision A_R(nel), A_I(nel), At_R(nel), At_I(nel)
integer i, j, ka, kb, l
* compute At_mnel (At_mnel(i) = number of non nul elements of row i of At)
call iset(n, 0, At_mnel, 1) ! init At_mnel with 0
do ka = 1, nel
j = A_icol(ka)
At_mnel(j) = At_mnel(j) + 1
enddo
* now compute ptr(i) such that it is the index in At_icol
* (and At_R and At_I) of the first non nul element of row i of At
call sz2ptr(At_mnel, n-1, ptr)
* now transpose
ka = 0
do i = 1, m
do l = 1, A_mnel(i)
ka = ka + 1
j = A_icol(ka)
kb = ptr(j)
At_icol(kb) = i
if ( it .ge. 0 ) At_R(kb) = A_R(ka)
if ( it .eq. 1 ) At_I(kb) = A_I(ka)
ptr(j) = ptr(j) + 1
enddo
enddo
end
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