SGTTRS solves one of the systems of equations


    A*X = B  or  A**T*X = B,


 with a tridiagonal matrix A using the LU factorization computed


 by SGTTRF.

TRANS

          TRANS is CHARACTER*1


          Specifies the form of the system of equations.


          = 'N':  A * X = B  (No transpose)


          = 'T':  A**T* X = B  (Transpose)


          = 'C':  A**T* X = B  (Conjugate transpose = Transpose)

N

          N is INTEGER


          The order of the matrix A.

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)


          The (n-1) multipliers that define the matrix L from the


          LU factorization of A.

D

          D is REAL array, dimension (N)


          The n diagonal elements of the upper triangular matrix U from


          the LU factorization of A.

DU

          DU is REAL array, dimension (N-1)


          The (n-1) elements of the first super-diagonal of U.

DU2

          DU2 is REAL array, dimension (N-2)


          The (n-2) elements of the second super-diagonal of U.

IPIV

          IPIV is INTEGER array, dimension (N)


          The pivot indices; for 1 <= i <= n, row i of the matrix was


          interchanged with row IPIV(i).  IPIV(i) will always be either


          i or i+1; IPIV(i) = i indicates a row interchange was not


          required.

B

          B is REAL array, dimension (LDB,NRHS)


          On entry, the matrix of right hand side vectors B.


          On exit, B is overwritten by 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 = -i, the i-th argument had an illegal value

Univ. of Tennessee

Univ. of California Berkeley

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NAG Ltd.

December 2016