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NAME
     ctbtrs - solve a triangular system of the form   A * X =  B,
     A**T * X = B, or A**H * X = B,

SYNOPSIS
     SUBROUTINE CTBTRS( UPLO, TRANS, DIAG, N, KD, NRHS, AB, LDAB,
               B, LDB, INFO )

     CHARACTER DIAG, TRANS, UPLO

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

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



     #include <sunperf.h>

     void ctbtrs(char uplo, char trans, char diag, int n, int kd,
               int nrhs, complex *cab, int ldab, complex *cb, int
               ldb, int *info) ;

PURPOSE
     CTBTRS solves a triangular system of the form

     where A is a triangular band matrix of order N, and B is  an
     N-by-NRHS  matrix.  A check is made to verify that A is non-
     singular.


ARGUMENTS
     UPLO      (input) CHARACTER*1
               = 'U':  A is upper triangular;
               = 'L':  A is lower triangular.

     TRANS     (input) CHARACTER*1
               Specifies the form of the system of equations:
               = 'N':  A * X = B     (No transpose)
               = 'T':  A**T * X = B  (Transpose)
               = 'C':  A**H * X = B  (Conjugate transpose)

     DIAG      (input) CHARACTER*1
               = 'N':  A is non-unit triangular;
               = 'U':  A is unit triangular.

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

     KD        (input) INTEGER
               The number of superdiagonals  or  subdiagonals  of
               the triangular band matrix A.  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) COMPLEX array, dimension (LDAB,N)
               The upper  or  lower  triangular  band  matrix  A,
               stored  in  the  first  kd+1 rows of AB.  The j-th
               column of A is stored in the j-th  column  of  the
               array  AB  as  follows:  if UPLO = 'U', AB(kd+1+i-
               j,j) = A(i,j) for  max(1,j-kd)<=i<=j;  if  UPLO  =
               'L',      AB(1+i-j,j)         =     A(i,j)     for
               j<=i<=min(n,j+kd).  If DIAG =  'U',  the  diagonal
               elements  of  A are not referenced and are assumed
               to be 1.

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

     B         (input/output) COMPLEX array, dimension (LDB,NRHS)
               On entry, the right hand side matrix B.  On  exit,
               if INFO = 0, 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 ille-
               gal value
               > 0:  if INFO = i, the i-th diagonal element of  A
               is  zero,  indicating  that the matrix is singular
               and the solutions X have not been computed.

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