ZPTTRS solves a tridiagonal system of the form


    A * X = B


 using the factorization A = U**H *D* U or A = L*D*L**H computed by ZPTTRF.


 D is a diagonal matrix specified in the vector D, U (or L) is a unit


 bidiagonal matrix whose superdiagonal (subdiagonal) is specified in


 the vector E, and X and B are N by NRHS matrices.

UPLO

          UPLO is CHARACTER*1


          Specifies the form of the factorization and whether the


          vector E is the superdiagonal of the upper bidiagonal factor


          U or the subdiagonal of the lower bidiagonal factor L.


          = 'U':  A = U**H *D*U, E is the superdiagonal of U


          = 'L':  A = L*D*L**H, E is the subdiagonal of L

N

          N is INTEGER


          The order of the tridiagonal matrix A.  N >= 0.

NRHS

          NRHS is INTEGER


          The number of right hand sides, i.e., the number of columns


          of the matrix B.  NRHS >= 0.

D

          D is DOUBLE PRECISION array, dimension (N)


          The n diagonal elements of the diagonal matrix D from the


          factorization A = U**H *D*U or A = L*D*L**H.

E

          E is COMPLEX*16 array, dimension (N-1)


          If UPLO = 'U', the (n-1) superdiagonal elements of the unit


          bidiagonal factor U from the factorization A = U**H*D*U.


          If UPLO = 'L', the (n-1) subdiagonal elements of the unit


          bidiagonal factor L from the factorization A = L*D*L**H.

B

          B is COMPLEX*16 array, dimension (LDB,NRHS)


          On entry, the right hand side vectors B for the system of


          linear equations.


          On exit, the solution vectors, X.

LDB

          LDB is INTEGER


          The leading dimension of the array B.  LDB >= max(1,N).

INFO

          INFO is INTEGER


          = 0: successful exit


          < 0: if INFO = -k, the k-th argument had an illegal value

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NAG Ltd.

June 2016