1DGTSV(1)                 LAPACK routine (version 3.2)                 DGTSV(1)
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NAME

6       DGTSV - solves the equation   A*X = B,
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SYNOPSIS

9       SUBROUTINE DGTSV( N, NRHS, DL, D, DU, B, LDB, INFO )
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11           INTEGER       INFO, LDB, N, NRHS
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13           DOUBLE        PRECISION B( LDB, * ), D( * ), DL( * ), DU( * )
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PURPOSE

16       DGTSV   solves the equation where A is an n by n tridiagonal matrix, by
17       Gaussian elimination with partial pivoting.
18       Note that the equation  A'*X = B  may be solved  by  interchanging  the
19       order of the arguments DU and DL.
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ARGUMENTS

22       N       (input) INTEGER
23               The order of the matrix A.  N >= 0.
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25       NRHS    (input) INTEGER
26               The  number of right hand sides, i.e., the number of columns of
27               the matrix B.  NRHS >= 0.
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29       DL      (input/output) DOUBLE PRECISION array, dimension (N-1)
30               On entry, DL must contain the (n-1) sub-diagonal elements of A.
31               On  exit, DL is overwritten by the (n-2) elements of the second
32               super-diagonal of the upper triangular matrix  U  from  the  LU
33               factorization of A, in DL(1), ..., DL(n-2).
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35       D       (input/output) DOUBLE PRECISION array, dimension (N)
36               On  entry, D must contain the diagonal elements of A.  On exit,
37               D is overwritten by the n diagonal elements of U.
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39       DU      (input/output) DOUBLE PRECISION array, dimension (N-1)
40               On entry, DU must contain the (n-1) super-diagonal elements  of
41               A.   On  exit,  DU  is overwritten by the (n-1) elements of the
42               first super-diagonal of U.
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44       B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
45               On entry, the N by NRHS matrix of right hand side matrix B.  On
46               exit, if INFO = 0, the N by NRHS solution matrix X.
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48       LDB     (input) INTEGER
49               The leading dimension of the array B.  LDB >= max(1,N).
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51       INFO    (output) INTEGER
52               = 0: successful exit
53               < 0: if INFO = -i, the i-th argument had an illegal value
54               >  0: if INFO = i, U(i,i) is exactly zero, and the solution has
55               not been computed.  The factorization has  not  been  completed
56               unless i = N.
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60 LAPACK routine (version 3.2)    November 2008                        DGTSV(1)