*DECK CDOTC COMPLEX FUNCTION CDOTC (N, CX, INCX, CY, INCY) C***BEGIN PROLOGUE CDOTC C***PURPOSE Dot product of two complex vectors using the complex C conjugate of the first vector. C***LIBRARY SLATEC (BLAS) C***CATEGORY D1A4 C***TYPE COMPLEX (CDOTC-C) C***KEYWORDS BLAS, INNER PRODUCT, LINEAR ALGEBRA, VECTOR C***AUTHOR Lawson, C. L., (JPL) C Hanson, R. J., (SNLA) C Kincaid, D. R., (U. of Texas) C Krogh, F. T., (JPL) C***DESCRIPTION C C B L A S Subprogram C Description of Parameters C C --Input-- C N number of elements in input vector(s) C CX complex vector with N elements C INCX storage spacing between elements of CX C CY complex vector with N elements C INCY storage spacing between elements of CY C C --Output-- C CDOTC complex result (zero if N .LE. 0) C C Returns the dot product of complex CX and CY, using CONJUGATE(CX) C CDOTC = SUM for I = 0 to N-1 of CONJ(CX(LX+I*INCX))*CY(LY+I*INCY), C where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and LY is C defined in a similar way using INCY. C C***REFERENCES C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T. C Krogh, Basic linear algebra subprograms for Fortran C usage, Algorithm No. 539, Transactions on Mathematical C Software 5, 3 (September 1979), pp. 308-323. C***ROUTINES CALLED (NONE) C***REVISION HISTORY (YYMMDD) C 791001 DATE WRITTEN C 890831 Modified array declarations. (WRB) C 890831 REVISION DATE from Version 3.2 C 891214 Prologue converted to Version 4.0 format. (BAB) C 920310 Corrected definition of LX in DESCRIPTION. (WRB) C 920501 Reformatted the REFERENCES section. (WRB) C***END PROLOGUE CDOTC COMPLEX CX(*),CY(*) C***FIRST EXECUTABLE STATEMENT CDOTC CDOTC = (0.0,0.0) IF (N .LE. 0) RETURN IF (INCX.EQ.INCY .AND. INCX.GT.0) GO TO 20 C C Code for unequal or nonpositive increments. C KX = 1 KY = 1 IF (INCX .LT. 0) KX = 1+(1-N)*INCX IF (INCY .LT. 0) KY = 1+(1-N)*INCY DO 10 I = 1,N CDOTC = CDOTC + CONJG(CX(KX))*CY(KY) KX = KX + INCX KY = KY + INCY 10 CONTINUE RETURN C C Code for equal, positive increments. C 20 NS = N*INCX DO 30 I = 1,NS,INCX CDOTC = CDOTC + CONJG(CX(I))*CY(I) 30 CONTINUE RETURN END