1DTBTRS(1)                LAPACK routine (version 3.1)                DTBTRS(1)
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NAME

6       DTBTRS - a triangular system of the form   A * X = B or A**T * X = B,
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SYNOPSIS

9       SUBROUTINE DTBTRS( UPLO,  TRANS,  DIAG,  N, KD, NRHS, AB, LDAB, B, LDB,
10                          INFO )
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12           CHARACTER      DIAG, TRANS, UPLO
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14           INTEGER        INFO, KD, LDAB, LDB, N, NRHS
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16           DOUBLE         PRECISION AB( LDAB, * ), B( LDB, * )
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PURPOSE

19       DTBTRS solves a triangular system of the form
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21       where A is a triangular band matrix of order N, and B is an  N-by  NRHS
22       matrix.  A check is made to verify that A is nonsingular.
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ARGUMENTS

26       UPLO    (input) CHARACTER*1
27               = 'U':  A is upper triangular;
28               = 'L':  A is lower triangular.
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30       TRANS   (input) CHARACTER*1
31               Specifies the form the system of equations:
32               = 'N':  A * X = B  (No transpose)
33               = 'T':  A**T * X = B  (Transpose)
34               = 'C':  A**H * X = B  (Conjugate transpose = Transpose)
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36       DIAG    (input) CHARACTER*1
37               = 'N':  A is non-unit triangular;
38               = 'U':  A is unit triangular.
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40       N       (input) INTEGER
41               The order of the matrix A.  N >= 0.
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43       KD      (input) INTEGER
44               The  number of superdiagonals or subdiagonals of the triangular
45               band matrix A.  KD >= 0.
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47       NRHS    (input) INTEGER
48               The number of right hand sides, i.e., the number of columns  of
49               the matrix B.  NRHS >= 0.
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51       AB      (input) DOUBLE PRECISION array, dimension (LDAB,N)
52               The  upper  or  lower  triangular  band matrix A, stored in the
53               first kd+1 rows of AB.  The j-th column of A is stored  in  the
54               j-th  column  of  the  array  AB  as  follows:  if  UPLO = 'U',
55               AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; if UPLO  =  'L',
56               AB(1+i-j,j)     = A(i,j) for j<=i<=min(n,j+kd).  If DIAG = 'U',
57               the diagonal elements of A are not referenced and  are  assumed
58               to be 1.
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60       LDAB    (input) INTEGER
61               The leading dimension of the array AB.  LDAB >= KD+1.
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63       B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
64               On  entry, the right hand side matrix B.  On exit, if INFO = 0,
65               the solution matrix X.
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67       LDB     (input) INTEGER
68               The leading dimension of the array B.  LDB >= max(1,N).
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70       INFO    (output) INTEGER
71               = 0:  successful exit
72               < 0:  if INFO = -i, the i-th argument had an illegal value
73               > 0:  if INFO = i, the i-th diagonal  element  of  A  is  zero,
74               indicating that the matrix is singular and the solutions X have
75               not been computed.
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79 LAPACK routine (version 3.1)    November 2006                       DTBTRS(1)
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