DPTTRS solves a tridiagonal system of the form


    A * X = B


 using the L*D*L**T factorization of A computed by DPTTRF.  D is a


 diagonal matrix specified in the vector D, L is a unit bidiagonal


 matrix whose subdiagonal is specified in the vector E, and X and B


 are N by NRHS matrices.

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


          L*D*L**T factorization of A.

E

          E is DOUBLE PRECISION array, dimension (N-1)


          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


          factorization A = U**T*D*U.

B

          B is DOUBLE PRECISION 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

Univ. of Tennessee

Univ. of California Berkeley

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NAG Ltd.

December 2016