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spbtrs

 NAME
      SPBTRS - solve a system of linear equations A*X = B with a
      symmetric positive definite band matrix A using the Cholesky
      factorization A = U**T*U or A = L*L**T computed by SPBTRF

 SYNOPSIS
      SUBROUTINE SPBTRS( UPLO, N, KD, NRHS, AB, LDAB, B, LDB, INFO
                         )

          CHARACTER      UPLO

          INTEGER        INFO, KD, LDAB, LDB, N, NRHS

          REAL           AB( LDAB, * ), B( LDB, * )

 PURPOSE
      SPBTRS solves a system of linear equations A*X = B with a
      symmetric positive definite band matrix A using the Cholesky
      factorization A = U**T*U or A = L*L**T computed by SPBTRF.

 ARGUMENTS
      UPLO    (input) CHARACTER*1
              = 'U':  Upper triangular factor stored in AB;
              = 'L':  Lower triangular factor stored in AB.

      N       (input) INTEGER
              The order of the matrix A.  N >= 0.

      KD      (input) INTEGER
              The number of superdiagonals of the matrix A if UPLO
              = 'U', or the number of subdiagonals if UPLO = 'L'.
              KD >= 0.

      NRHS    (input) INTEGER
              The number of right hand sides, i.e., the number of
              columns of the matrix B.  NRHS >= 0.

      AB      (input) REAL array, dimension (LDAB,N)
              The triangular factor U or L from the Cholesky fac-
              torization A = U**T*U or A = L*L**T of the band
              matrix A, stored in the first KD+1 rows of the
              array.  The j-th column of U or L is stored in the
              array AB as follows: if UPLO ='U', AB(kd+1+i-j,j) =
              U(i,j) for max(1,j-kd)<=i<=j; if UPLO ='L', AB(1+i-
              j,j)    = L(i,j) for j<=i<=min(n,j+kd).

      LDAB    (input) INTEGER
              The leading dimension of the array AB.  LDAB >=
              KD+1.

      B       (input/output) REAL array, dimension (LDB,NRHS)

              On entry, the right hand side matrix B.  On exit,
              the solution matrix X.

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

      INFO    (output) INTEGER
              = 0:  successful exit
              < 0:  if INFO = -i, the i-th argument had an illegal
              value