subroutine ctslz(a,x,r,m,l,lda)
integer m,l,lda
double complex a(lda,l),x(m,l),r(1)
c
c ctslz solves the double complex linear system
c a * x = b
c with the ct - matrix a .
c
c on entry
c
c a double complex(2*m - 1,l)
c the first row of blocks of the ct - matrix .
c each block is represented by its first row
c followed by its first column beginning with the
c second element. on return a has been destroyed .
c
c x double complex(m*l)
c the right hand side vector b .
c
c r double complex(max(2*m - 2,2*l))
c a work vector .
c
c m integer
c the order of the blocks of the matrix a .
c
c l integer
c the number of blocks in a row or column
c of the matrix a .
c
c lda integer
c the leading dimension of the array a .
c
c on return
c
c x the solution vector .
c
c toeplitz package. this version dated 07/23/82 .
c
c subroutines and functions
c
c toeplitz package ... salwz,tslz
c fortran ... dfloat
c
c internal variables
c
integer i1,i2
double precision rl
c
rl = dfloat(l)
c
c reduce the ct - matrix to a block-diagonal matrix
c by the inverse discrete fourier transformation .
c
call salwz(a,r,r(l+1),2*m - 1,l,lda,-1)
c
c compute the discrete fourier transformation of
c the right hand side vector .
c
call salwz(x,r,r(l+1),m,l,m,1)
c
c solve the block-diagonal system, blocks of which
c are t - matrices .
c
do 10 i2 = 1, l
call tslz(a(1,i2),x(1,i2),r,m)
10 continue
c
c compute the solution of the given system by
c the inverse discrete fourier transformation .
c
call salwz(x,r,r(l+1),m,l,m,-1)
c
do 30 i2 = 1, l
do 20 i1 = 1, m
x(i1,i2) = x(i1,i2)/rl
20 continue
30 continue
return
end