Annotation of rpl/lapack/lapack/dsyswapr.f, revision 1.3
1.3 ! bertrand 1: SUBROUTINE DSYSWAPR( UPLO, N, A, LDA, I1, I2)
1.1 bertrand 2: *
1.3 ! bertrand 3: * -- LAPACK auxiliary routine (version 3.3.1) --
1.1 bertrand 4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.3 ! bertrand 6: * -- April 2011 --
1.1 bertrand 7: *
8: * .. Scalar Arguments ..
9: CHARACTER UPLO
1.3 ! bertrand 10: INTEGER I1, I2, LDA, N
1.1 bertrand 11: * ..
12: * .. Array Arguments ..
1.3 ! bertrand 13: DOUBLE PRECISION A( LDA, N )
1.1 bertrand 14: *
15: * Purpose
16: * =======
17: *
18: * DSYSWAPR applies an elementary permutation on the rows and the columns of
19: * a symmetric matrix.
20: *
21: * Arguments
22: * =========
23: *
24: * UPLO (input) CHARACTER*1
25: * Specifies whether the details of the factorization are stored
26: * as an upper or lower triangular matrix.
27: * = 'U': Upper triangular, form is A = U*D*U**T;
28: * = 'L': Lower triangular, form is A = L*D*L**T.
29: *
30: * N (input) INTEGER
31: * The order of the matrix A. N >= 0.
32: *
33: * A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
34: * On entry, the NB diagonal matrix D and the multipliers
35: * used to obtain the factor U or L as computed by DSYTRF.
36: *
37: * On exit, if INFO = 0, the (symmetric) inverse of the original
38: * matrix. If UPLO = 'U', the upper triangular part of the
39: * inverse is formed and the part of A below the diagonal is not
40: * referenced; if UPLO = 'L' the lower triangular part of the
41: * inverse is formed and the part of A above the diagonal is
42: * not referenced.
43: *
1.3 ! bertrand 44: * LDA (input) INTEGER
! 45: * The leading dimension of the array A. LDA >= max(1,N).
! 46: *
1.1 bertrand 47: * I1 (input) INTEGER
48: * Index of the first row to swap
49: *
50: * I2 (input) INTEGER
51: * Index of the second row to swap
52: *
53: * =====================================================================
54: *
55: * ..
56: * .. Local Scalars ..
57: LOGICAL UPPER
58: INTEGER I
59: DOUBLE PRECISION TMP
60: *
61: * .. External Functions ..
62: LOGICAL LSAME
63: EXTERNAL LSAME
64: * ..
65: * .. External Subroutines ..
66: EXTERNAL DSWAP
67: * ..
68: * .. Executable Statements ..
69: *
70: UPPER = LSAME( UPLO, 'U' )
71: IF (UPPER) THEN
72: *
73: * UPPER
74: * first swap
75: * - swap column I1 and I2 from I1 to I1-1
76: CALL DSWAP( I1-1, A(1,I1), 1, A(1,I2), 1 )
77: *
78: * second swap :
79: * - swap A(I1,I1) and A(I2,I2)
80: * - swap row I1 from I1+1 to I2-1 with col I2 from I1+1 to I2-1
81: TMP=A(I1,I1)
82: A(I1,I1)=A(I2,I2)
83: A(I2,I2)=TMP
84: *
85: DO I=1,I2-I1-1
86: TMP=A(I1,I1+I)
87: A(I1,I1+I)=A(I1+I,I2)
88: A(I1+I,I2)=TMP
89: END DO
90: *
91: * third swap
92: * - swap row I1 and I2 from I2+1 to N
93: DO I=I2+1,N
94: TMP=A(I1,I)
95: A(I1,I)=A(I2,I)
96: A(I2,I)=TMP
97: END DO
98: *
99: ELSE
100: *
101: * LOWER
102: * first swap
103: * - swap row I1 and I2 from I1 to I1-1
1.3 ! bertrand 104: CALL DSWAP( I1-1, A(I1,1), LDA, A(I2,1), LDA )
1.1 bertrand 105: *
106: * second swap :
107: * - swap A(I1,I1) and A(I2,I2)
108: * - swap col I1 from I1+1 to I2-1 with row I2 from I1+1 to I2-1
109: TMP=A(I1,I1)
110: A(I1,I1)=A(I2,I2)
111: A(I2,I2)=TMP
112: *
113: DO I=1,I2-I1-1
114: TMP=A(I1+I,I1)
115: A(I1+I,I1)=A(I2,I1+I)
116: A(I2,I1+I)=TMP
117: END DO
118: *
119: * third swap
120: * - swap col I1 and I2 from I2+1 to N
121: DO I=I2+1,N
122: TMP=A(I,I1)
123: A(I,I1)=A(I,I2)
124: A(I,I2)=TMP
125: END DO
126: *
127: ENDIF
128: END SUBROUTINE DSYSWAPR
129:
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