| SUBROUTINE SROTM(N,SX,INCX,SY,INCY,SPARAM) |
| * .. Scalar Arguments .. |
| INTEGER INCX,INCY,N |
| * .. |
| * .. Array Arguments .. |
| REAL SPARAM(5),SX(*),SY(*) |
| * .. |
| * |
| * Purpose |
| * ======= |
| * |
| * APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX |
| * |
| * (SX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF SX ARE IN |
| * (DX**T) |
| * |
| * SX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE |
| * LX = (-INCX)*N, AND SIMILARLY FOR SY USING USING LY AND INCY. |
| * 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). |
| * SEE SROTMG FOR A DESCRIPTION OF DATA STORAGE IN SPARAM. |
| * |
| * |
| * Arguments |
| * ========= |
| * |
| * N (input) INTEGER |
| * number of elements in input vector(s) |
| * |
| * SX (input/output) REAL array, dimension N |
| * double precision vector with N elements |
| * |
| * INCX (input) INTEGER |
| * storage spacing between elements of SX |
| * |
| * SY (input/output) REAL array, dimension N |
| * double precision vector with N elements |
| * |
| * INCY (input) INTEGER |
| * storage spacing between elements of SY |
| * |
| * SPARAM (input/output) REAL array, dimension 5 |
| * SPARAM(1)=SFLAG |
| * SPARAM(2)=SH11 |
| * SPARAM(3)=SH21 |
| * SPARAM(4)=SH12 |
| * SPARAM(5)=SH22 |
| * |
| * ===================================================================== |
| * |
| * .. Local Scalars .. |
| REAL SFLAG,SH11,SH12,SH21,SH22,TWO,W,Z,ZERO |
| INTEGER I,KX,KY,NSTEPS |
| * .. |
| * .. Data statements .. |
| DATA ZERO,TWO/0.E0,2.E0/ |
| * .. |
| * |
| SFLAG = SPARAM(1) |
| IF (N.LE.0 .OR. (SFLAG+TWO.EQ.ZERO)) GO TO 140 |
| IF (.NOT. (INCX.EQ.INCY.AND.INCX.GT.0)) GO TO 70 |
| * |
| NSTEPS = N*INCX |
| IF (SFLAG) 50,10,30 |
| 10 CONTINUE |
| SH12 = SPARAM(4) |
| SH21 = SPARAM(3) |
| DO 20 I = 1,NSTEPS,INCX |
| W = SX(I) |
| Z = SY(I) |
| SX(I) = W + Z*SH12 |
| SY(I) = W*SH21 + Z |
| 20 CONTINUE |
| GO TO 140 |
| 30 CONTINUE |
| SH11 = SPARAM(2) |
| SH22 = SPARAM(5) |
| DO 40 I = 1,NSTEPS,INCX |
| W = SX(I) |
| Z = SY(I) |
| SX(I) = W*SH11 + Z |
| SY(I) = -W + SH22*Z |
| 40 CONTINUE |
| GO TO 140 |
| 50 CONTINUE |
| SH11 = SPARAM(2) |
| SH12 = SPARAM(4) |
| SH21 = SPARAM(3) |
| SH22 = SPARAM(5) |
| DO 60 I = 1,NSTEPS,INCX |
| W = SX(I) |
| Z = SY(I) |
| SX(I) = W*SH11 + Z*SH12 |
| SY(I) = W*SH21 + Z*SH22 |
| 60 CONTINUE |
| GO TO 140 |
| 70 CONTINUE |
| KX = 1 |
| KY = 1 |
| IF (INCX.LT.0) KX = 1 + (1-N)*INCX |
| IF (INCY.LT.0) KY = 1 + (1-N)*INCY |
| * |
| IF (SFLAG) 120,80,100 |
| 80 CONTINUE |
| SH12 = SPARAM(4) |
| SH21 = SPARAM(3) |
| DO 90 I = 1,N |
| W = SX(KX) |
| Z = SY(KY) |
| SX(KX) = W + Z*SH12 |
| SY(KY) = W*SH21 + Z |
| KX = KX + INCX |
| KY = KY + INCY |
| 90 CONTINUE |
| GO TO 140 |
| 100 CONTINUE |
| SH11 = SPARAM(2) |
| SH22 = SPARAM(5) |
| DO 110 I = 1,N |
| W = SX(KX) |
| Z = SY(KY) |
| SX(KX) = W*SH11 + Z |
| SY(KY) = -W + SH22*Z |
| KX = KX + INCX |
| KY = KY + INCY |
| 110 CONTINUE |
| GO TO 140 |
| 120 CONTINUE |
| SH11 = SPARAM(2) |
| SH12 = SPARAM(4) |
| SH21 = SPARAM(3) |
| SH22 = SPARAM(5) |
| DO 130 I = 1,N |
| W = SX(KX) |
| Z = SY(KY) |
| SX(KX) = W*SH11 + Z*SH12 |
| SY(KY) = W*SH21 + Z*SH22 |
| KX = KX + INCX |
| KY = KY + INCY |
| 130 CONTINUE |
| 140 CONTINUE |
| RETURN |
| END |
