-
Notifications
You must be signed in to change notification settings - Fork 0
/
drotmg.f
251 lines (240 loc) · 6.26 KB
/
drotmg.f
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
*> \brief \b DROTMG
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE DROTMG(DD1,DD2,DX1,DY1,DPARAM)
*
* .. Scalar Arguments ..
* DOUBLE PRECISION DD1,DD2,DX1,DY1
* ..
* .. Array Arguments ..
* DOUBLE PRECISION DPARAM(5)
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS
*> THE SECOND COMPONENT OF THE 2-VECTOR (DSQRT(DD1)*DX1,DSQRT(DD2)*> DY2)**T.
*> WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
*>
*> DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0
*>
*> (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0)
*> H=( ) ( ) ( ) ( )
*> (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0).
*> LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22
*> RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE
*> VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.)
*>
*> THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE
*> INEXACT. THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE
*> OF DD1 AND DD2. ALL ACTUAL SCALING OF DATA IS DONE USING GAM.
*>
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in,out] DD1
*> \verbatim
*> DD1 is DOUBLE PRECISION
*> \endverbatim
*>
*> \param[in,out] DD2
*> \verbatim
*> DD2 is DOUBLE PRECISION
*> \endverbatim
*>
*> \param[in,out] DX1
*> \verbatim
*> DX1 is DOUBLE PRECISION
*> \endverbatim
*>
*> \param[in] DY1
*> \verbatim
*> DY1 is DOUBLE PRECISION
*> \endverbatim
*>
*> \param[in,out] DPARAM
*> \verbatim
*> DPARAM is DOUBLE PRECISION array, dimension 5
*> DPARAM(1)=DFLAG
*> DPARAM(2)=DH11
*> DPARAM(3)=DH21
*> DPARAM(4)=DH12
*> DPARAM(5)=DH22
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup double_blas_level1
*
* =====================================================================
SUBROUTINE DROTMG(DD1,DD2,DX1,DY1,DPARAM)
*
* -- Reference BLAS level1 routine (version 3.4.0) --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2011
*
* .. Scalar Arguments ..
DOUBLE PRECISION DD1,DD2,DX1,DY1
* ..
* .. Array Arguments ..
DOUBLE PRECISION DPARAM(5)
* ..
*
* =====================================================================
*
* .. Local Scalars ..
DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,DP1,DP2,DQ1,DQ2,DTEMP,
$ DU,GAM,GAMSQ,ONE,RGAMSQ,TWO,ZERO
* ..
* .. Intrinsic Functions ..
INTRINSIC DABS
* ..
* .. Data statements ..
*
DATA ZERO,ONE,TWO/0.D0,1.D0,2.D0/
DATA GAM,GAMSQ,RGAMSQ/4096.D0,16777216.D0,5.9604645D-8/
* ..
IF (DD1.LT.ZERO) THEN
* GO ZERO-H-D-AND-DX1..
DFLAG = -ONE
DH11 = ZERO
DH12 = ZERO
DH21 = ZERO
DH22 = ZERO
*
DD1 = ZERO
DD2 = ZERO
DX1 = ZERO
ELSE
* CASE-DD1-NONNEGATIVE
DP2 = DD2*DY1
IF (DP2.EQ.ZERO) THEN
DFLAG = -TWO
DPARAM(1) = DFLAG
RETURN
END IF
* REGULAR-CASE..
DP1 = DD1*DX1
DQ2 = DP2*DY1
DQ1 = DP1*DX1
*
IF (DABS(DQ1).GT.DABS(DQ2)) THEN
DH21 = -DY1/DX1
DH12 = DP2/DP1
*
DU = ONE - DH12*DH21
*
IF (DU.GT.ZERO) THEN
DFLAG = ZERO
DD1 = DD1/DU
DD2 = DD2/DU
DX1 = DX1*DU
END IF
ELSE
IF (DQ2.LT.ZERO) THEN
* GO ZERO-H-D-AND-DX1..
DFLAG = -ONE
DH11 = ZERO
DH12 = ZERO
DH21 = ZERO
DH22 = ZERO
*
DD1 = ZERO
DD2 = ZERO
DX1 = ZERO
ELSE
DFLAG = ONE
DH11 = DP1/DP2
DH22 = DX1/DY1
DU = ONE + DH11*DH22
DTEMP = DD2/DU
DD2 = DD1/DU
DD1 = DTEMP
DX1 = DY1*DU
END IF
END IF
* PROCEDURE..SCALE-CHECK
IF (DD1.NE.ZERO) THEN
DO WHILE ((DD1.LE.RGAMSQ) .OR. (DD1.GE.GAMSQ))
IF (DFLAG.EQ.ZERO) THEN
DH11 = ONE
DH22 = ONE
DFLAG = -ONE
ELSE
DH21 = -ONE
DH12 = ONE
DFLAG = -ONE
END IF
IF (DD1.LE.RGAMSQ) THEN
DD1 = DD1*GAM**2
DX1 = DX1/GAM
DH11 = DH11/GAM
DH12 = DH12/GAM
ELSE
DD1 = DD1/GAM**2
DX1 = DX1*GAM
DH11 = DH11*GAM
DH12 = DH12*GAM
END IF
ENDDO
END IF
IF (DD2.NE.ZERO) THEN
DO WHILE ( (DABS(DD2).LE.RGAMSQ) .OR. (DABS(DD2).GE.GAMSQ) )
IF (DFLAG.EQ.ZERO) THEN
DH11 = ONE
DH22 = ONE
DFLAG = -ONE
ELSE
DH21 = -ONE
DH12 = ONE
DFLAG = -ONE
END IF
IF (DABS(DD2).LE.RGAMSQ) THEN
DD2 = DD2*GAM**2
DH21 = DH21/GAM
DH22 = DH22/GAM
ELSE
DD2 = DD2/GAM**2
DH21 = DH21*GAM
DH22 = DH22*GAM
END IF
END DO
END IF
END IF
IF (DFLAG.LT.ZERO) THEN
DPARAM(2) = DH11
DPARAM(3) = DH21
DPARAM(4) = DH12
DPARAM(5) = DH22
ELSE IF (DFLAG.EQ.ZERO) THEN
DPARAM(3) = DH21
DPARAM(4) = DH12
ELSE
DPARAM(2) = DH11
DPARAM(5) = DH22
END IF
DPARAM(1) = DFLAG
RETURN
END