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71 lines
2.6 KiB
Fortran
71 lines
2.6 KiB
Fortran
*DECK CDCDOT
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COMPLEX FUNCTION CDCDOT (N, CB, CX, INCX, CY, INCY)
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C***BEGIN PROLOGUE CDCDOT
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C***PURPOSE Compute the inner product of two vectors with extended
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C precision accumulation.
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C***LIBRARY SLATEC (BLAS)
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C***CATEGORY D1A4
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C***TYPE COMPLEX (SDSDOT-S, CDCDOT-C)
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C***KEYWORDS BLAS, DOT PRODUCT, INNER PRODUCT, LINEAR ALGEBRA, VECTOR
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C***AUTHOR Lawson, C. L., (JPL)
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C Hanson, R. J., (SNLA)
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C Kincaid, D. R., (U. of Texas)
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C Krogh, F. T., (JPL)
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C***DESCRIPTION
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C
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C B L A S Subprogram
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C Description of Parameters
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C
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C --Input--
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C N number of elements in input vector(s)
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C CB complex scalar to be added to inner product
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C CX complex vector with N elements
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C INCX storage spacing between elements of CX
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C CY complex vector with N elements
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C INCY storage spacing between elements of CY
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C
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C --Output--
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C CDCDOT complex dot product (CB if N .LE. 0)
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C
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C Returns complex result with dot product accumulated in D.P.
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C CDCDOT = CB + sum for I = 0 to N-1 of CX(LX+I*INCY)*CY(LY+I*INCY)
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C where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and LY is
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C defined in a similar way using INCY.
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C
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C***REFERENCES C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T.
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C Krogh, Basic linear algebra subprograms for Fortran
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C usage, Algorithm No. 539, Transactions on Mathematical
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C Software 5, 3 (September 1979), pp. 308-323.
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C***ROUTINES CALLED (NONE)
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C***REVISION HISTORY (YYMMDD)
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C 791001 DATE WRITTEN
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C 890531 Changed all specific intrinsics to generic. (WRB)
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C 890531 REVISION DATE from Version 3.2
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C 920310 Corrected definition of LX in DESCRIPTION. (WRB)
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C 920501 Reformatted the REFERENCES section. (WRB)
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C***END PROLOGUE CDCDOT
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INTEGER N, INCX, INCY, I, KX, KY
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COMPLEX CX(*), CY(*), CB
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DOUBLE PRECISION DSDOTR, DSDOTI, DT1, DT2, DT3, DT4
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C***FIRST EXECUTABLE STATEMENT CDCDOT
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DSDOTR = DBLE(REAL(CB))
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DSDOTI = DBLE(AIMAG(CB))
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IF (N .LE. 0) GO TO 10
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KX = 1
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KY = 1
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IF(INCX.LT.0) KX = 1+(1-N)*INCX
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IF(INCY.LT.0) KY = 1+(1-N)*INCY
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DO 5 I = 1,N
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DT1 = DBLE(REAL(CX(KX)))
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DT2 = DBLE(REAL(CY(KY)))
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DT3 = DBLE(AIMAG(CX(KX)))
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DT4 = DBLE(AIMAG(CY(KY)))
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DSDOTR = DSDOTR+(DT1*DT2)-(DT3*DT4)
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DSDOTI = DSDOTI+(DT1*DT4)+(DT3*DT2)
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KX = KX+INCX
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KY = KY+INCY
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5 CONTINUE
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10 CDCDOT = CMPLX(REAL(DSDOTR),REAL(DSDOTI))
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RETURN
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END
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