Annotation of rpl/lapack/blas/drotm.f, revision 1.17
1.9 bertrand 1: *> \brief \b DROTM
1.1 bertrand 2: *
1.9 bertrand 3: * =========== DOCUMENTATION ===========
1.1 bertrand 4: *
1.14 bertrand 5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
1.1 bertrand 7: *
1.9 bertrand 8: * Definition:
9: * ===========
10: *
11: * SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM)
1.14 bertrand 12: *
1.9 bertrand 13: * .. Scalar Arguments ..
14: * INTEGER INCX,INCY,N
15: * ..
16: * .. Array Arguments ..
17: * DOUBLE PRECISION DPARAM(5),DX(*),DY(*)
18: * ..
1.14 bertrand 19: *
1.9 bertrand 20: *
21: *> \par Purpose:
22: * =============
23: *>
24: *> \verbatim
25: *>
26: *> APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX
27: *>
28: *> (DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN
29: *> (DY**T)
30: *>
31: *> DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
32: *> LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY.
33: *> WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
34: *>
35: *> DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0
36: *>
37: *> (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0)
38: *> H=( ) ( ) ( ) ( )
39: *> (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0).
40: *> SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM.
41: *> \endverbatim
42: *
43: * Arguments:
44: * ==========
45: *
46: *> \param[in] N
47: *> \verbatim
48: *> N is INTEGER
49: *> number of elements in input vector(s)
50: *> \endverbatim
51: *>
52: *> \param[in,out] DX
53: *> \verbatim
1.15 bertrand 54: *> DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
1.9 bertrand 55: *> \endverbatim
56: *>
57: *> \param[in] INCX
58: *> \verbatim
59: *> INCX is INTEGER
60: *> storage spacing between elements of DX
61: *> \endverbatim
62: *>
63: *> \param[in,out] DY
64: *> \verbatim
1.15 bertrand 65: *> DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
1.9 bertrand 66: *> \endverbatim
67: *>
68: *> \param[in] INCY
69: *> \verbatim
70: *> INCY is INTEGER
71: *> storage spacing between elements of DY
72: *> \endverbatim
73: *>
1.15 bertrand 74: *> \param[in] DPARAM
1.9 bertrand 75: *> \verbatim
1.15 bertrand 76: *> DPARAM is DOUBLE PRECISION array, dimension (5)
1.9 bertrand 77: *> DPARAM(1)=DFLAG
78: *> DPARAM(2)=DH11
79: *> DPARAM(3)=DH21
80: *> DPARAM(4)=DH12
81: *> DPARAM(5)=DH22
82: *> \endverbatim
83: *
84: * Authors:
85: * ========
86: *
1.14 bertrand 87: *> \author Univ. of Tennessee
88: *> \author Univ. of California Berkeley
89: *> \author Univ. of Colorado Denver
90: *> \author NAG Ltd.
1.1 bertrand 91: *
1.9 bertrand 92: *> \ingroup double_blas_level1
1.1 bertrand 93: *
1.9 bertrand 94: * =====================================================================
95: SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM)
1.1 bertrand 96: *
1.17 ! bertrand 97: * -- Reference BLAS level1 routine --
1.9 bertrand 98: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
99: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.1 bertrand 100: *
1.9 bertrand 101: * .. Scalar Arguments ..
102: INTEGER INCX,INCY,N
103: * ..
104: * .. Array Arguments ..
105: DOUBLE PRECISION DPARAM(5),DX(*),DY(*)
106: * ..
1.1 bertrand 107: *
108: * =====================================================================
109: *
110: * .. Local Scalars ..
111: DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,TWO,W,Z,ZERO
112: INTEGER I,KX,KY,NSTEPS
113: * ..
114: * .. Data statements ..
115: DATA ZERO,TWO/0.D0,2.D0/
116: * ..
117: *
118: DFLAG = DPARAM(1)
1.8 bertrand 119: IF (N.LE.0 .OR. (DFLAG+TWO.EQ.ZERO)) RETURN
120: IF (INCX.EQ.INCY.AND.INCX.GT.0) THEN
1.1 bertrand 121: *
1.8 bertrand 122: NSTEPS = N*INCX
123: IF (DFLAG.LT.ZERO) THEN
124: DH11 = DPARAM(2)
125: DH12 = DPARAM(4)
126: DH21 = DPARAM(3)
127: DH22 = DPARAM(5)
128: DO I = 1,NSTEPS,INCX
129: W = DX(I)
130: Z = DY(I)
131: DX(I) = W*DH11 + Z*DH12
132: DY(I) = W*DH21 + Z*DH22
133: END DO
134: ELSE IF (DFLAG.EQ.ZERO) THEN
135: DH12 = DPARAM(4)
136: DH21 = DPARAM(3)
137: DO I = 1,NSTEPS,INCX
138: W = DX(I)
139: Z = DY(I)
140: DX(I) = W + Z*DH12
141: DY(I) = W*DH21 + Z
142: END DO
143: ELSE
144: DH11 = DPARAM(2)
145: DH22 = DPARAM(5)
146: DO I = 1,NSTEPS,INCX
147: W = DX(I)
148: Z = DY(I)
149: DX(I) = W*DH11 + Z
150: DY(I) = -W + DH22*Z
151: END DO
152: END IF
1.4 bertrand 153: ELSE
1.8 bertrand 154: KX = 1
155: KY = 1
156: IF (INCX.LT.0) KX = 1 + (1-N)*INCX
157: IF (INCY.LT.0) KY = 1 + (1-N)*INCY
1.1 bertrand 158: *
1.8 bertrand 159: IF (DFLAG.LT.ZERO) THEN
160: DH11 = DPARAM(2)
161: DH12 = DPARAM(4)
162: DH21 = DPARAM(3)
163: DH22 = DPARAM(5)
164: DO I = 1,N
165: W = DX(KX)
166: Z = DY(KY)
167: DX(KX) = W*DH11 + Z*DH12
168: DY(KY) = W*DH21 + Z*DH22
169: KX = KX + INCX
170: KY = KY + INCY
171: END DO
172: ELSE IF (DFLAG.EQ.ZERO) THEN
173: DH12 = DPARAM(4)
174: DH21 = DPARAM(3)
175: DO I = 1,N
176: W = DX(KX)
177: Z = DY(KY)
178: DX(KX) = W + Z*DH12
179: DY(KY) = W*DH21 + Z
180: KX = KX + INCX
181: KY = KY + INCY
182: END DO
183: ELSE
184: DH11 = DPARAM(2)
185: DH22 = DPARAM(5)
186: DO I = 1,N
187: W = DX(KX)
188: Z = DY(KY)
189: DX(KX) = W*DH11 + Z
190: DY(KY) = -W + DH22*Z
191: KX = KX + INCX
192: KY = KY + INCY
193: END DO
194: END IF
1.4 bertrand 195: END IF
1.1 bertrand 196: RETURN
1.17 ! bertrand 197: *
! 198: * End of DROTM
! 199: *
1.1 bertrand 200: END
CVSweb interface <joel.bertrand@systella.fr>
![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to drotm.f CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [local] / rpl / lapack / blas