Statistiques
| Révision :

root / src / blas / srotm.f @ 4

Historique | Voir | Annoter | Télécharger (3,63 ko)

1 
      SUBROUTINE SROTM(N,SX,INCX,SY,INCY,SPARAM)
2 
*     .. Scalar Arguments ..
3 
      INTEGER INCX,INCY,N
4 
*     ..
5 
*     .. Array Arguments ..
6 
      REAL SPARAM(5),SX(1),SY(1)
7 
*     ..
8 
*
9 
*  Purpose
10 
*  =======
11 
*
12 
*     APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX
13 
*
14 
*     (SX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF SX ARE IN
15 
*     (DX**T)
16 
*
17 
*     SX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
18 
*     LX = (-INCX)*N, AND SIMILARLY FOR SY USING USING LY AND INCY.
19 
*     WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS..
20 
*
21 
*     SFLAG=-1.E0     SFLAG=0.E0        SFLAG=1.E0     SFLAG=-2.E0
22 
*
23 
*       (SH11  SH12)    (1.E0  SH12)    (SH11  1.E0)    (1.E0  0.E0)
24 
*     H=(          )    (          )    (          )    (          )
25 
*       (SH21  SH22),   (SH21  1.E0),   (-1.E0 SH22),   (0.E0  1.E0).
26 
*     SEE  SROTMG FOR A DESCRIPTION OF DATA STORAGE IN SPARAM.
27 
*
28 
*
29 
*  Arguments
30 
*  =========
31 
*
32 
*  N      (input) INTEGER
33 
*         number of elements in input vector(s)
34 
*
35 
*  SX     (input/output) REAL array, dimension N
36 
*         double precision vector with 5 elements
37 
*
38 
*  INCX   (input) INTEGER
39 
*         storage spacing between elements of SX
40 
*
41 
*  SY     (input/output) REAL array, dimension N
42 
*         double precision vector with N elements
43 
*
44 
*  INCY   (input) INTEGER
45 
*         storage spacing between elements of SY
46 
*
47 
*  SPARAM (input/output)  REAL array, dimension 5
48 
*     SPARAM(1)=SFLAG
49 
*     SPARAM(2)=SH11
50 
*     SPARAM(3)=SH21
51 
*     SPARAM(4)=SH12
52 
*     SPARAM(5)=SH22
53 
*
54 
*  =====================================================================
55 
*
56 
*     .. Local Scalars ..
57 
      REAL SFLAG,SH11,SH12,SH21,SH22,TWO,W,Z,ZERO
58 
      INTEGER I,KX,KY,NSTEPS
59 
*     ..
60 
*     .. Data statements ..
61 
      DATA ZERO,TWO/0.E0,2.E0/
62 
*     ..
63 
*
64 
      SFLAG = SPARAM(1)
65 
      IF (N.LE.0 .OR. (SFLAG+TWO.EQ.ZERO)) GO TO 140
66 
      IF (.NOT. (INCX.EQ.INCY.AND.INCX.GT.0)) GO TO 70
67 
*
68 
      NSTEPS = N*INCX
69 
      IF (SFLAG) 50,10,30
70 
   10 CONTINUE
71 
      SH12 = SPARAM(4)
72 
      SH21 = SPARAM(3)
73 
      DO 20 I = 1,NSTEPS,INCX
74 
          W = SX(I)
75 
          Z = SY(I)
76 
          SX(I) = W + Z*SH12
77 
          SY(I) = W*SH21 + Z
78 
   20 CONTINUE
79 
      GO TO 140
80 
   30 CONTINUE
81 
      SH11 = SPARAM(2)
82 
      SH22 = SPARAM(5)
83 
      DO 40 I = 1,NSTEPS,INCX
84 
          W = SX(I)
85 
          Z = SY(I)
86 
          SX(I) = W*SH11 + Z
87 
          SY(I) = -W + SH22*Z
88 
   40 CONTINUE
89 
      GO TO 140
90 
   50 CONTINUE
91 
      SH11 = SPARAM(2)
92 
      SH12 = SPARAM(4)
93 
      SH21 = SPARAM(3)
94 
      SH22 = SPARAM(5)
95 
      DO 60 I = 1,NSTEPS,INCX
96 
          W = SX(I)
97 
          Z = SY(I)
98 
          SX(I) = W*SH11 + Z*SH12
99 
          SY(I) = W*SH21 + Z*SH22
100 
   60 CONTINUE
101 
      GO TO 140
102 
   70 CONTINUE
103 
      KX = 1
104 
      KY = 1
105 
      IF (INCX.LT.0) KX = 1 + (1-N)*INCX
106 
      IF (INCY.LT.0) KY = 1 + (1-N)*INCY
107 
*
108 
      IF (SFLAG) 120,80,100
109 
   80 CONTINUE
110 
      SH12 = SPARAM(4)
111 
      SH21 = SPARAM(3)
112 
      DO 90 I = 1,N
113 
          W = SX(KX)
114 
          Z = SY(KY)
115 
          SX(KX) = W + Z*SH12
116 
          SY(KY) = W*SH21 + Z
117 
          KX = KX + INCX
118 
          KY = KY + INCY
119 
   90 CONTINUE
120 
      GO TO 140
121 
  100 CONTINUE
122 
      SH11 = SPARAM(2)
123 
      SH22 = SPARAM(5)
124 
      DO 110 I = 1,N
125 
          W = SX(KX)
126 
          Z = SY(KY)
127 
          SX(KX) = W*SH11 + Z
128 
          SY(KY) = -W + SH22*Z
129 
          KX = KX + INCX
130 
          KY = KY + INCY
131 
  110 CONTINUE
132 
      GO TO 140
133 
  120 CONTINUE
134 
      SH11 = SPARAM(2)
135 
      SH12 = SPARAM(4)
136 
      SH21 = SPARAM(3)
137 
      SH22 = SPARAM(5)
138 
      DO 130 I = 1,N
139 
          W = SX(KX)
140 
          Z = SY(KY)
141 
          SX(KX) = W*SH11 + Z*SH12
142 
          SY(KY) = W*SH21 + Z*SH22
143 
          KX = KX + INCX
144 
          KY = KY + INCY
145 
  130 CONTINUE
146 
  140 CONTINUE
147 
      RETURN
148 
      END