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.LT.ZERO) THEN GO TO 50 ELSE IF (SFLAG.EQ.ZERO) THEN GO TO 10 ELSE GO TO 30 END IF 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.LT.ZERO) THEN GO TO 120 ELSE IF (SFLAG.EQ.ZERO) THEN GO TO 80 ELSE GO TO 100 END IF 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