1DGTTS2(1) LAPACK auxiliary routine (version 3.1) DGTTS2(1)
2
3
4
6 DGTTS2 - one of the systems of equations A*X = B or A'*X = B,
7
9 SUBROUTINE DGTTS2( ITRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB )
10
11 INTEGER ITRANS, LDB, N, NRHS
12
13 INTEGER IPIV( * )
14
15 DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ), DU( * ),
16 DU2( * )
17
19 DGTTS2 solves one of the systems of equations
20 A*X = B or A'*X = B, with a tridiagonal matrix A using the LU fac‐
21 torization computed by DGTTRF.
22
23
25 ITRANS (input) INTEGER
26 Specifies the form of the system of equations. = 0: A * X = B
27 (No transpose)
28 = 1: A'* X = B (Transpose)
29 = 2: A'* X = B (Conjugate transpose = Transpose)
30
31 N (input) INTEGER
32 The order of the matrix A.
33
34 NRHS (input) INTEGER
35 The number of right hand sides, i.e., the number of columns of
36 the matrix B. NRHS >= 0.
37
38 DL (input) DOUBLE PRECISION array, dimension (N-1)
39 The (n-1) multipliers that define the matrix L from the LU fac‐
40 torization of A.
41
42 D (input) DOUBLE PRECISION array, dimension (N)
43 The n diagonal elements of the upper triangular matrix U from
44 the LU factorization of A.
45
46 DU (input) DOUBLE PRECISION array, dimension (N-1)
47 The (n-1) elements of the first super-diagonal of U.
48
49 DU2 (input) DOUBLE PRECISION array, dimension (N-2)
50 The (n-2) elements of the second super-diagonal of U.
51
52 IPIV (input) INTEGER array, dimension (N)
53 The pivot indices; for 1 <= i <= n, row i of the matrix was
54 interchanged with row IPIV(i). IPIV(i) will always be either i
55 or i+1; IPIV(i) = i indicates a row interchange was not
56 required.
57
58 B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
59 On entry, the matrix of right hand side vectors B. On exit, B
60 is overwritten by the solution vectors X.
61
62 LDB (input) INTEGER
63 The leading dimension of the array B. LDB >= max(1,N).
64
65
66
67 LAPACK auxiliary routine (versionNo3v.e1m)ber 2006 DGTTS2(1)