SGTSV  solves the equation


    A*X = B,


 where A is an n by n tridiagonal matrix, by Gaussian elimination with


 partial pivoting.


 Note that the equation  A**T*X = B  may be solved by interchanging the


 order of the arguments DU and DL.

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.

DL

          DL is REAL array, dimension (N-1)


          On entry, DL must contain the (n-1) sub-diagonal elements of


          A.


          On exit, DL is overwritten by the (n-2) elements of the


          second super-diagonal of the upper triangular matrix U from


          the LU factorization of A, in DL(1), ..., DL(n-2).

D

          D is REAL array, dimension (N)


          On entry, D must contain the diagonal elements of A.


          On exit, D is overwritten by the n diagonal elements of U.

DU

          DU is REAL array, dimension (N-1)


          On entry, DU must contain the (n-1) super-diagonal elements


          of A.


          On exit, DU is overwritten by the (n-1) elements of the first


          super-diagonal of U.

B

          B is REAL array, dimension (LDB,NRHS)


          On entry, the N by NRHS matrix of 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, U(i,i) is exactly zero, 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