Annotation of rpl/lapack/lapack/dsyswapr.f, revision 1.4
1.4 ! bertrand 1: *> \brief \b DSYSWAPR
! 2: *
! 3: * =========== DOCUMENTATION ===========
! 4: *
! 5: * Online html documentation available at
! 6: * http://www.netlib.org/lapack/explore-html/
! 7: *
! 8: *> \htmlonly
! 9: *> Download DSYSWAPR + dependencies
! 10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dsyswapr.f">
! 11: *> [TGZ]</a>
! 12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dsyswapr.f">
! 13: *> [ZIP]</a>
! 14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dsyswapr.f">
! 15: *> [TXT]</a>
! 16: *> \endhtmlonly
! 17: *
! 18: * Definition:
! 19: * ===========
! 20: *
! 21: * SUBROUTINE DSYSWAPR( UPLO, N, A, LDA, I1, I2)
! 22: *
! 23: * .. Scalar Arguments ..
! 24: * CHARACTER UPLO
! 25: * INTEGER I1, I2, LDA, N
! 26: * ..
! 27: * .. Array Arguments ..
! 28: * DOUBLE PRECISION A( LDA, N )
! 29: *
! 30: *
! 31: *> \par Purpose:
! 32: * =============
! 33: *>
! 34: *> \verbatim
! 35: *>
! 36: *> DSYSWAPR applies an elementary permutation on the rows and the columns of
! 37: *> a symmetric matrix.
! 38: *> \endverbatim
! 39: *
! 40: * Arguments:
! 41: * ==========
! 42: *
! 43: *> \param[in] UPLO
! 44: *> \verbatim
! 45: *> UPLO is CHARACTER*1
! 46: *> Specifies whether the details of the factorization are stored
! 47: *> as an upper or lower triangular matrix.
! 48: *> = 'U': Upper triangular, form is A = U*D*U**T;
! 49: *> = 'L': Lower triangular, form is A = L*D*L**T.
! 50: *> \endverbatim
! 51: *>
! 52: *> \param[in] N
! 53: *> \verbatim
! 54: *> N is INTEGER
! 55: *> The order of the matrix A. N >= 0.
! 56: *> \endverbatim
! 57: *>
! 58: *> \param[in,out] A
! 59: *> \verbatim
! 60: *> A is DOUBLE PRECISION array, dimension (LDA,N)
! 61: *> On entry, the NB diagonal matrix D and the multipliers
! 62: *> used to obtain the factor U or L as computed by DSYTRF.
! 63: *>
! 64: *> On exit, if INFO = 0, the (symmetric) inverse of the original
! 65: *> matrix. If UPLO = 'U', the upper triangular part of the
! 66: *> inverse is formed and the part of A below the diagonal is not
! 67: *> referenced; if UPLO = 'L' the lower triangular part of the
! 68: *> inverse is formed and the part of A above the diagonal is
! 69: *> not referenced.
! 70: *> \endverbatim
! 71: *>
! 72: *> \param[in] LDA
! 73: *> \verbatim
! 74: *> LDA is INTEGER
! 75: *> The leading dimension of the array A. LDA >= max(1,N).
! 76: *> \endverbatim
! 77: *>
! 78: *> \param[in] I1
! 79: *> \verbatim
! 80: *> I1 is INTEGER
! 81: *> Index of the first row to swap
! 82: *> \endverbatim
! 83: *>
! 84: *> \param[in] I2
! 85: *> \verbatim
! 86: *> I2 is INTEGER
! 87: *> Index of the second row to swap
! 88: *> \endverbatim
! 89: *
! 90: * Authors:
! 91: * ========
! 92: *
! 93: *> \author Univ. of Tennessee
! 94: *> \author Univ. of California Berkeley
! 95: *> \author Univ. of Colorado Denver
! 96: *> \author NAG Ltd.
! 97: *
! 98: *> \date November 2011
! 99: *
! 100: *> \ingroup doubleSYauxiliary
! 101: *
! 102: * =====================================================================
1.3 bertrand 103: SUBROUTINE DSYSWAPR( UPLO, N, A, LDA, I1, I2)
1.1 bertrand 104: *
1.4 ! bertrand 105: * -- LAPACK auxiliary routine (version 3.4.0) --
1.1 bertrand 106: * -- LAPACK is a software package provided by Univ. of Tennessee, --
107: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.4 ! bertrand 108: * November 2011
1.1 bertrand 109: *
110: * .. Scalar Arguments ..
111: CHARACTER UPLO
1.3 bertrand 112: INTEGER I1, I2, LDA, N
1.1 bertrand 113: * ..
114: * .. Array Arguments ..
1.3 bertrand 115: DOUBLE PRECISION A( LDA, N )
1.1 bertrand 116: *
117: * =====================================================================
118: *
119: * ..
120: * .. Local Scalars ..
121: LOGICAL UPPER
122: INTEGER I
123: DOUBLE PRECISION TMP
124: *
125: * .. External Functions ..
126: LOGICAL LSAME
127: EXTERNAL LSAME
128: * ..
129: * .. External Subroutines ..
130: EXTERNAL DSWAP
131: * ..
132: * .. Executable Statements ..
133: *
134: UPPER = LSAME( UPLO, 'U' )
135: IF (UPPER) THEN
136: *
137: * UPPER
138: * first swap
139: * - swap column I1 and I2 from I1 to I1-1
140: CALL DSWAP( I1-1, A(1,I1), 1, A(1,I2), 1 )
141: *
142: * second swap :
143: * - swap A(I1,I1) and A(I2,I2)
144: * - swap row I1 from I1+1 to I2-1 with col I2 from I1+1 to I2-1
145: TMP=A(I1,I1)
146: A(I1,I1)=A(I2,I2)
147: A(I2,I2)=TMP
148: *
149: DO I=1,I2-I1-1
150: TMP=A(I1,I1+I)
151: A(I1,I1+I)=A(I1+I,I2)
152: A(I1+I,I2)=TMP
153: END DO
154: *
155: * third swap
156: * - swap row I1 and I2 from I2+1 to N
157: DO I=I2+1,N
158: TMP=A(I1,I)
159: A(I1,I)=A(I2,I)
160: A(I2,I)=TMP
161: END DO
162: *
163: ELSE
164: *
165: * LOWER
166: * first swap
167: * - swap row I1 and I2 from I1 to I1-1
1.3 bertrand 168: CALL DSWAP( I1-1, A(I1,1), LDA, A(I2,1), LDA )
1.1 bertrand 169: *
170: * second swap :
171: * - swap A(I1,I1) and A(I2,I2)
172: * - swap col I1 from I1+1 to I2-1 with row I2 from I1+1 to I2-1
173: TMP=A(I1,I1)
174: A(I1,I1)=A(I2,I2)
175: A(I2,I2)=TMP
176: *
177: DO I=1,I2-I1-1
178: TMP=A(I1+I,I1)
179: A(I1+I,I1)=A(I2,I1+I)
180: A(I2,I1+I)=TMP
181: END DO
182: *
183: * third swap
184: * - swap col I1 and I2 from I2+1 to N
185: DO I=I2+1,N
186: TMP=A(I,I1)
187: A(I,I1)=A(I,I2)
188: A(I,I2)=TMP
189: END DO
190: *
191: ENDIF
192: END SUBROUTINE DSYSWAPR
193:
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