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 SROTMG
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE SROTMG(SD1,SD2,SX1,SY1,SPARAM)
*
* .. Scalar Arguments ..
* REAL SD1,SD2,SX1,SY1
* ..
* .. Array Arguments ..
* REAL SPARAM(5)
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS
*> THE SECOND COMPONENT OF THE 2-VECTOR (SQRT(SD1)*SX1,SQRT(SD2)*> SY2)**T.
*> WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS..
*>
*> SFLAG=-1.E0 SFLAG=0.E0 SFLAG=1.E0 SFLAG=-2.E0
*>
*> (SH11 SH12) (1.E0 SH12) (SH11 1.E0) (1.E0 0.E0)
*> H=( ) ( ) ( ) ( )
*> (SH21 SH22), (SH21 1.E0), (-1.E0 SH22), (0.E0 1.E0).
*> LOCATIONS 2-4 OF SPARAM CONTAIN SH11,SH21,SH12, AND SH22
*> RESPECTIVELY. (VALUES OF 1.E0, -1.E0, OR 0.E0 IMPLIED BY THE
*> VALUE OF SPARAM(1) ARE NOT STORED IN SPARAM.)
*>
*> 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 SD1 AND SD2. ALL ACTUAL SCALING OF DATA IS DONE USING GAM.
*>
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in,out] SD1
*> \verbatim
*> SD1 is REAL
*> \endverbatim
*>
*> \param[in,out] SD2
*> \verbatim
*> SD2 is REAL
*> \endverbatim
*>
*> \param[in,out] SX1
*> \verbatim
*> SX1 is REAL
*> \endverbatim
*>
*> \param[in] SY1
*> \verbatim
*> SY1 is REAL
*> \endverbatim
*>
*> \param[in,out] SPARAM
*> \verbatim
*> SPARAM is REAL array, dimension 5
*> SPARAM(1)=SFLAG
*> SPARAM(2)=SH11
*> SPARAM(3)=SH21
*> SPARAM(4)=SH12
*> SPARAM(5)=SH22
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup single_blas_level1
*
* =====================================================================
SUBROUTINE SROTMG(SD1,SD2,SX1,SY1,SPARAM)
*
* -- 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 ..
REAL SD1,SD2,SX1,SY1
* ..
* .. Array Arguments ..
REAL SPARAM(5)
* ..
*
* =====================================================================
*
* .. Local Scalars ..
REAL GAM,GAMSQ,ONE,RGAMSQ,SFLAG,SH11,SH12,SH21,SH22,SP1,SP2,SQ1,
$ SQ2,STEMP,SU,TWO,ZERO
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS
* ..
* .. Data statements ..
*
DATA ZERO,ONE,TWO/0.E0,1.E0,2.E0/
DATA GAM,GAMSQ,RGAMSQ/4096.E0,1.67772E7,5.96046E-8/
* ..
IF (SD1.LT.ZERO) THEN
* GO ZERO-H-D-AND-SX1..
SFLAG = -ONE
SH11 = ZERO
SH12 = ZERO
SH21 = ZERO
SH22 = ZERO
*
SD1 = ZERO
SD2 = ZERO
SX1 = ZERO
ELSE
* CASE-SD1-NONNEGATIVE
SP2 = SD2*SY1
IF (SP2.EQ.ZERO) THEN
SFLAG = -TWO
SPARAM(1) = SFLAG
RETURN
END IF
* REGULAR-CASE..
SP1 = SD1*SX1
SQ2 = SP2*SY1
SQ1 = SP1*SX1
*
IF (ABS(SQ1).GT.ABS(SQ2)) THEN
SH21 = -SY1/SX1
SH12 = SP2/SP1
*
SU = ONE - SH12*SH21
*
IF (SU.GT.ZERO) THEN
SFLAG = ZERO
SD1 = SD1/SU
SD2 = SD2/SU
SX1 = SX1*SU
END IF
ELSE
IF (SQ2.LT.ZERO) THEN
* GO ZERO-H-D-AND-SX1..
SFLAG = -ONE
SH11 = ZERO
SH12 = ZERO
SH21 = ZERO
SH22 = ZERO
*
SD1 = ZERO
SD2 = ZERO
SX1 = ZERO
ELSE
SFLAG = ONE
SH11 = SP1/SP2
SH22 = SX1/SY1
SU = ONE + SH11*SH22
STEMP = SD2/SU
SD2 = SD1/SU
SD1 = STEMP
SX1 = SY1*SU
END IF
END IF
* PROCESURE..SCALE-CHECK
IF (SD1.NE.ZERO) THEN
DO WHILE ((SD1.LE.RGAMSQ) .OR. (SD1.GE.GAMSQ))
IF (SFLAG.EQ.ZERO) THEN
SH11 = ONE
SH22 = ONE
SFLAG = -ONE
ELSE
SH21 = -ONE
SH12 = ONE
SFLAG = -ONE
END IF
IF (SD1.LE.RGAMSQ) THEN
SD1 = SD1*GAM**2
SX1 = SX1/GAM
SH11 = SH11/GAM
SH12 = SH12/GAM
ELSE
SD1 = SD1/GAM**2
SX1 = SX1*GAM
SH11 = SH11*GAM
SH12 = SH12*GAM
END IF
ENDDO
END IF
IF (SD2.NE.ZERO) THEN
DO WHILE ( (ABS(SD2).LE.RGAMSQ) .OR. (ABS(SD2).GE.GAMSQ) )
IF (SFLAG.EQ.ZERO) THEN
SH11 = ONE
SH22 = ONE
SFLAG = -ONE
ELSE
SH21 = -ONE
SH12 = ONE
SFLAG = -ONE
END IF
IF (ABS(SD2).LE.RGAMSQ) THEN
SD2 = SD2*GAM**2
SH21 = SH21/GAM
SH22 = SH22/GAM
ELSE
SD2 = SD2/GAM**2
SH21 = SH21*GAM
SH22 = SH22*GAM
END IF
END DO
END IF
END IF
IF (SFLAG.LT.ZERO) THEN
SPARAM(2) = SH11
SPARAM(3) = SH21
SPARAM(4) = SH12
SPARAM(5) = SH22
ELSE IF (SFLAG.EQ.ZERO) THEN
SPARAM(3) = SH21
SPARAM(4) = SH12
ELSE
SPARAM(2) = SH11
SPARAM(5) = SH22
END IF
SPARAM(1) = SFLAG
RETURN
END
|
