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90 lines
3.3 KiB
Fortran
90 lines
3.3 KiB
Fortran
*DECK DQDOTI
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DOUBLE PRECISION FUNCTION DQDOTI (N, DB, QC, DX, INCX, DY, INCY)
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C***BEGIN PROLOGUE DQDOTI
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C***PURPOSE Compute the inner product of two vectors with extended
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C precision accumulation and result.
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C***LIBRARY SLATEC
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C***CATEGORY D1A4
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C***TYPE DOUBLE PRECISION (DQDOTI-D)
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C***KEYWORDS DOT PRODUCT, INNER PRODUCT
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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 DB double precision scalar to be added to inner product
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C QC extended precision scalar to be added
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C DX double precision vector with N elements
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C INCX storage spacing between elements of DX
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C DY double precision vector with N elements
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C INCY storage spacing between elements of DY
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C
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C --Output--
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C DQDOTI double precision result
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C QC extended precision result
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C
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C D.P. dot product with extended precision accumulation (and result)
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C QC and DQDOTI are set = DB + sum for I = 0 to N-1 of
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C DX(LX+I*INCX) * DY(LY+I*INCY), where QC is an extended
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C precision result which can be used as input to DQDOTA,
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C and LX = 1 if INCX .GE. 0, else LX = (-INCX)*N, and LY is
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C defined in a similar way using INCY. The MP package by
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C Richard P. Brent is used for the extended precision arithmetic.
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C
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C Fred T. Krogh, JPL, 1977, June 1
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C
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C The common block for the MP package is named MPCOM. If local
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C variable I1 is zero, DQDOTI calls MPBLAS to initialize the MP
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C package and reset I1 to 1.
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C
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C The argument QC(*), and the local variables QX and QY are INTEGER
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C arrays of size 30. See the comments in the routine MPBLAS for the
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C reason for this choice.
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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 MPADD, MPBLAS, MPCDM, MPCMD, MPMUL
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C***COMMON BLOCKS MPCOM
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C***REVISION HISTORY (YYMMDD)
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C 791001 DATE WRITTEN
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C 890831 Modified array declarations. (WRB)
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C 890831 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 920501 Reformatted the REFERENCES section. (WRB)
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C 930124 Increased Array sizes for SUN -r8. (RWC)
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C***END PROLOGUE DQDOTI
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DOUBLE PRECISION DX(*), DY(*), DB
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INTEGER QC(30), QX(30), QY(30)
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COMMON /MPCOM/ MPB, MPT, MPM, MPLUN, MPMXR, MPR(30)
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SAVE I1
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DATA I1 / 0 /
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C***FIRST EXECUTABLE STATEMENT DQDOTI
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IF (I1 .EQ. 0) CALL MPBLAS(I1)
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QC(1) = 0
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IF (DB .EQ. 0.D0) GO TO 60
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CALL MPCDM(DB, QX)
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CALL MPADD(QC, QX, QC)
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60 IF (N .EQ. 0) GO TO 80
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IX = 1
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IY = 1
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IF (INCX .LT. 0) IX = (-N + 1) * INCX + 1
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IF (INCY .LT. 0) IY = (-N + 1) * INCY + 1
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DO 70 I = 1,N
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CALL MPCDM(DX(IX), QX)
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CALL MPCDM(DY(IY), QY)
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CALL MPMUL(QX, QY, QX)
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CALL MPADD(QC, QX, QC)
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IX = IX + INCX
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IY = IY + INCY
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70 CONTINUE
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80 CALL MPCMD(QC, DQDOTI)
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RETURN
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END
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