Annotation of rpl/lapack/blas/drotm.f, revision 1.12
1.9 bertrand 1: *> \brief \b DROTM
1.1 bertrand 2: *
1.9 bertrand 3: * =========== DOCUMENTATION ===========
1.1 bertrand 4: *
1.9 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)
12: *
13: * .. Scalar Arguments ..
14: * INTEGER INCX,INCY,N
15: * ..
16: * .. Array Arguments ..
17: * DOUBLE PRECISION DPARAM(5),DX(*),DY(*)
18: * ..
19: *
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
54: *> DX is DOUBLE PRECISION array, dimension N
55: *> double precision vector with N elements
56: *> \endverbatim
57: *>
58: *> \param[in] INCX
59: *> \verbatim
60: *> INCX is INTEGER
61: *> storage spacing between elements of DX
62: *> \endverbatim
63: *>
64: *> \param[in,out] DY
65: *> \verbatim
66: *> DY is DOUBLE PRECISION array, dimension N
67: *> double precision vector with N elements
68: *> \endverbatim
69: *>
70: *> \param[in] INCY
71: *> \verbatim
72: *> INCY is INTEGER
73: *> storage spacing between elements of DY
74: *> \endverbatim
75: *>
76: *> \param[in,out] DPARAM
77: *> \verbatim
78: *> DPARAM is DOUBLE PRECISION array, dimension 5
79: *> DPARAM(1)=DFLAG
80: *> DPARAM(2)=DH11
81: *> DPARAM(3)=DH21
82: *> DPARAM(4)=DH12
83: *> DPARAM(5)=DH22
84: *> \endverbatim
85: *
86: * Authors:
87: * ========
88: *
89: *> \author Univ. of Tennessee
90: *> \author Univ. of California Berkeley
91: *> \author Univ. of Colorado Denver
92: *> \author NAG Ltd.
1.1 bertrand 93: *
1.9 bertrand 94: *> \date November 2011
1.1 bertrand 95: *
1.9 bertrand 96: *> \ingroup double_blas_level1
1.1 bertrand 97: *
1.9 bertrand 98: * =====================================================================
99: SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM)
1.1 bertrand 100: *
1.9 bertrand 101: * -- Reference BLAS level1 routine (version 3.4.0) --
102: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
103: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
104: * November 2011
1.1 bertrand 105: *
1.9 bertrand 106: * .. Scalar Arguments ..
107: INTEGER INCX,INCY,N
108: * ..
109: * .. Array Arguments ..
110: DOUBLE PRECISION DPARAM(5),DX(*),DY(*)
111: * ..
1.1 bertrand 112: *
113: * =====================================================================
114: *
115: * .. Local Scalars ..
116: DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,TWO,W,Z,ZERO
117: INTEGER I,KX,KY,NSTEPS
118: * ..
119: * .. Data statements ..
120: DATA ZERO,TWO/0.D0,2.D0/
121: * ..
122: *
123: DFLAG = DPARAM(1)
1.8 bertrand 124: IF (N.LE.0 .OR. (DFLAG+TWO.EQ.ZERO)) RETURN
125: IF (INCX.EQ.INCY.AND.INCX.GT.0) THEN
1.1 bertrand 126: *
1.8 bertrand 127: NSTEPS = N*INCX
128: IF (DFLAG.LT.ZERO) THEN
129: DH11 = DPARAM(2)
130: DH12 = DPARAM(4)
131: DH21 = DPARAM(3)
132: DH22 = DPARAM(5)
133: DO I = 1,NSTEPS,INCX
134: W = DX(I)
135: Z = DY(I)
136: DX(I) = W*DH11 + Z*DH12
137: DY(I) = W*DH21 + Z*DH22
138: END DO
139: ELSE IF (DFLAG.EQ.ZERO) THEN
140: DH12 = DPARAM(4)
141: DH21 = DPARAM(3)
142: DO I = 1,NSTEPS,INCX
143: W = DX(I)
144: Z = DY(I)
145: DX(I) = W + Z*DH12
146: DY(I) = W*DH21 + Z
147: END DO
148: ELSE
149: DH11 = DPARAM(2)
150: DH22 = DPARAM(5)
151: DO I = 1,NSTEPS,INCX
152: W = DX(I)
153: Z = DY(I)
154: DX(I) = W*DH11 + Z
155: DY(I) = -W + DH22*Z
156: END DO
157: END IF
1.4 bertrand 158: ELSE
1.8 bertrand 159: KX = 1
160: KY = 1
161: IF (INCX.LT.0) KX = 1 + (1-N)*INCX
162: IF (INCY.LT.0) KY = 1 + (1-N)*INCY
1.1 bertrand 163: *
1.8 bertrand 164: IF (DFLAG.LT.ZERO) THEN
165: DH11 = DPARAM(2)
166: DH12 = DPARAM(4)
167: DH21 = DPARAM(3)
168: DH22 = DPARAM(5)
169: DO I = 1,N
170: W = DX(KX)
171: Z = DY(KY)
172: DX(KX) = W*DH11 + Z*DH12
173: DY(KY) = W*DH21 + Z*DH22
174: KX = KX + INCX
175: KY = KY + INCY
176: END DO
177: ELSE IF (DFLAG.EQ.ZERO) THEN
178: DH12 = DPARAM(4)
179: DH21 = DPARAM(3)
180: DO I = 1,N
181: W = DX(KX)
182: Z = DY(KY)
183: DX(KX) = W + Z*DH12
184: DY(KY) = W*DH21 + Z
185: KX = KX + INCX
186: KY = KY + INCY
187: END DO
188: ELSE
189: DH11 = DPARAM(2)
190: DH22 = DPARAM(5)
191: DO I = 1,N
192: W = DX(KX)
193: Z = DY(KY)
194: DX(KX) = W*DH11 + Z
195: DY(KY) = -W + DH22*Z
196: KX = KX + INCX
197: KY = KY + INCY
198: END DO
199: END IF
1.4 bertrand 200: END IF
1.1 bertrand 201: RETURN
202: END
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