1: SUBROUTINE DTRTTP( UPLO, N, A, LDA, AP, INFO )
2: *
3: * -- LAPACK routine (version 3.2) --
4: * -- Contributed by Fred Gustavson of the IBM Watson Research Center --
5: * -- and Julien Langou of the Univ. of Colorado Denver --
6: * -- November 2008 --
7: *
8: * -- LAPACK is a software package provided by Univ. of Tennessee, --
9: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
10: *
11: * .. Scalar Arguments ..
12: CHARACTER UPLO
13: INTEGER INFO, N, LDA
14: * ..
15: * .. Array Arguments ..
16: DOUBLE PRECISION A( LDA, * ), AP( * )
17: * ..
18: *
19: * Purpose
20: * =======
21: *
22: * DTRTTP copies a triangular matrix A from full format (TR) to standard
23: * packed format (TP).
24: *
25: * Arguments
26: * =========
27: *
28: * UPLO (input) CHARACTER
29: * = 'U': A is upper triangular.
30: * = 'L': A is lower triangular.
31: *
32: * N (input) INTEGER
33: * The order of the matrices AP and A. N >= 0.
34: *
35: * A (input) DOUBLE PRECISION array, dimension (LDA,N)
36: * On exit, the triangular matrix A. If UPLO = 'U', the leading
37: * N-by-N upper triangular part of A contains the upper
38: * triangular part of the matrix A, and the strictly lower
39: * triangular part of A is not referenced. If UPLO = 'L', the
40: * leading N-by-N lower triangular part of A contains the lower
41: * triangular part of the matrix A, and the strictly upper
42: * triangular part of A is not referenced.
43: *
44: * LDA (input) INTEGER
45: * The leading dimension of the array A. LDA >= max(1,N).
46: *
47: * AP (output) DOUBLE PRECISION array, dimension (N*(N+1)/2
48: * On exit, the upper or lower triangular matrix A, packed
49: * columnwise in a linear array. The j-th column of A is stored
50: * in the array AP as follows:
51: * if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
52: * if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
53: *
54: * INFO (output) INTEGER
55: * = 0: successful exit
56: * < 0: if INFO = -i, the i-th argument had an illegal value
57: *
58: * =====================================================================
59: *
60: * .. Parameters ..
61: * ..
62: * .. Local Scalars ..
63: LOGICAL LOWER
64: INTEGER I, J, K
65: * ..
66: * .. External Functions ..
67: LOGICAL LSAME
68: EXTERNAL LSAME
69: * ..
70: * .. External Subroutines ..
71: EXTERNAL XERBLA
72: * ..
73: * .. Executable Statements ..
74: *
75: * Test the input parameters.
76: *
77: INFO = 0
78: LOWER = LSAME( UPLO, 'L' )
79: IF( .NOT.LOWER .AND. .NOT.LSAME( UPLO, 'U' ) ) THEN
80: INFO = -1
81: ELSE IF( N.LT.0 ) THEN
82: INFO = -2
83: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
84: INFO = -4
85: END IF
86: IF( INFO.NE.0 ) THEN
87: CALL XERBLA( 'DTRTTP', -INFO )
88: RETURN
89: END IF
90: *
91: IF( LOWER ) THEN
92: K = 0
93: DO J = 1, N
94: DO I = J, N
95: K = K + 1
96: AP( K ) = A( I, J )
97: END DO
98: END DO
99: ELSE
100: K = 0
101: DO J = 1, N
102: DO I = 1, J
103: K = K + 1
104: AP( K ) = A( I, J )
105: END DO
106: END DO
107: END IF
108: *
109: *
110: RETURN
111: *
112: * End of DTRTTP
113: *
114: END
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