SPTSV computes the solution to a real system of linear equations


 A*X = B, where A is an N-by-N symmetric positive definite tridiagonal


 matrix, and X and B are N-by-NRHS matrices.


 A is factored as A = L*D*L**T, and the factored form of A is then


 used to solve the system of equations.

N

          N is INTEGER


          The order of the 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 REAL array, dimension (N)


          On entry, the n diagonal elements of the tridiagonal matrix


          A.  On exit, the n diagonal elements of the diagonal matrix


          D from the factorization A = L*D*L**T.

E

          E is REAL array, dimension (N-1)


          On entry, the (n-1) subdiagonal elements of the tridiagonal


          matrix A.  On exit, the (n-1) subdiagonal elements of the


          unit bidiagonal factor L from the L*D*L**T factorization of


          A.  (E can also be regarded as the superdiagonal of the unit


          bidiagonal factor U from the U**T*D*U factorization of A.)

B

          B is REAL array, dimension (LDB,NRHS)


          On entry, the N-by-NRHS right hand side matrix B.


          On exit, if INFO = 0, the N-by-NRHS solution matrix 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 = -i, the i-th argument had an illegal value


          > 0:  if INFO = i, the leading minor of order i is not


                positive definite, and the solution has not been


                computed.  The factorization has not been completed


                unless i = N.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

December 2016