Annotation of rpl/lapack/lapack/zptsv.f, revision 1.5
1.1 bertrand 1: SUBROUTINE ZPTSV( N, NRHS, D, E, B, LDB, INFO )
2: *
3: * -- LAPACK routine (version 3.2) --
4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
6: * November 2006
7: *
8: * .. Scalar Arguments ..
9: INTEGER INFO, LDB, N, NRHS
10: * ..
11: * .. Array Arguments ..
12: DOUBLE PRECISION D( * )
13: COMPLEX*16 B( LDB, * ), E( * )
14: * ..
15: *
16: * Purpose
17: * =======
18: *
19: * ZPTSV computes the solution to a complex system of linear equations
20: * A*X = B, where A is an N-by-N Hermitian positive definite tridiagonal
21: * matrix, and X and B are N-by-NRHS matrices.
22: *
23: * A is factored as A = L*D*L**H, and the factored form of A is then
24: * used to solve the system of equations.
25: *
26: * Arguments
27: * =========
28: *
29: * N (input) INTEGER
30: * The order of the matrix A. N >= 0.
31: *
32: * NRHS (input) INTEGER
33: * The number of right hand sides, i.e., the number of columns
34: * of the matrix B. NRHS >= 0.
35: *
36: * D (input/output) DOUBLE PRECISION array, dimension (N)
37: * On entry, the n diagonal elements of the tridiagonal matrix
38: * A. On exit, the n diagonal elements of the diagonal matrix
39: * D from the factorization A = L*D*L**H.
40: *
41: * E (input/output) COMPLEX*16 array, dimension (N-1)
42: * On entry, the (n-1) subdiagonal elements of the tridiagonal
43: * matrix A. On exit, the (n-1) subdiagonal elements of the
44: * unit bidiagonal factor L from the L*D*L**H factorization of
45: * A. E can also be regarded as the superdiagonal of the unit
46: * bidiagonal factor U from the U**H*D*U factorization of A.
47: *
48: * B (input/output) COMPLEX*16 array, dimension (LDB,N)
49: * On entry, the N-by-NRHS right hand side matrix B.
50: * On exit, if INFO = 0, the N-by-NRHS solution matrix X.
51: *
52: * LDB (input) INTEGER
53: * The leading dimension of the array B. LDB >= max(1,N).
54: *
55: * INFO (output) INTEGER
56: * = 0: successful exit
57: * < 0: if INFO = -i, the i-th argument had an illegal value
58: * > 0: if INFO = i, the leading minor of order i is not
59: * positive definite, and the solution has not been
60: * computed. The factorization has not been completed
61: * unless i = N.
62: *
63: * =====================================================================
64: *
65: * .. External Subroutines ..
66: EXTERNAL XERBLA, ZPTTRF, ZPTTRS
67: * ..
68: * .. Intrinsic Functions ..
69: INTRINSIC MAX
70: * ..
71: * .. Executable Statements ..
72: *
73: * Test the input parameters.
74: *
75: INFO = 0
76: IF( N.LT.0 ) THEN
77: INFO = -1
78: ELSE IF( NRHS.LT.0 ) THEN
79: INFO = -2
80: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
81: INFO = -6
82: END IF
83: IF( INFO.NE.0 ) THEN
84: CALL XERBLA( 'ZPTSV ', -INFO )
85: RETURN
86: END IF
87: *
88: * Compute the L*D*L' (or U'*D*U) factorization of A.
89: *
90: CALL ZPTTRF( N, D, E, INFO )
91: IF( INFO.EQ.0 ) THEN
92: *
93: * Solve the system A*X = B, overwriting B with X.
94: *
95: CALL ZPTTRS( 'Lower', N, NRHS, D, E, B, LDB, INFO )
96: END IF
97: RETURN
98: *
99: * End of ZPTSV
100: *
101: END
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