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71 lines
2.3 KiB
Fortran
71 lines
2.3 KiB
Fortran
*DECK SCASUM
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FUNCTION SCASUM (N, CX, INCX)
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C***BEGIN PROLOGUE SCASUM
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C***PURPOSE Compute the sum of the magnitudes of the real and
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C imaginary elements of a complex vector.
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C***LIBRARY SLATEC (BLAS)
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C***CATEGORY D1A3A
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C***TYPE COMPLEX (SASUM-S, DASUM-D, SCASUM-C)
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C***KEYWORDS BLAS, LINEAR ALGEBRA, SUM OF MAGNITUDES OF A 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 CX complex vector with N elements
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C INCX storage spacing between elements of CX
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C
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C --Output--
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C SCASUM single precision result (zero if N .LE. 0)
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C
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C Returns sums of magnitudes of real and imaginary parts of
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C components of CX. Note that this is not the L1 norm of CX.
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C CASUM = sum from 0 to N-1 of ABS(REAL(CX(IX+I*INCX))) +
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C ABS(IMAG(CX(IX+I*INCX))),
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C where IX = 1 if INCX .GE. 0, else IX = 1+(1-N)*INCX.
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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 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 900821 Modified to correct problem with a negative increment.
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C (WRB)
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C 920501 Reformatted the REFERENCES section. (WRB)
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C***END PROLOGUE SCASUM
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COMPLEX CX(*)
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INTEGER I, INCX, IX, N
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C***FIRST EXECUTABLE STATEMENT SCASUM
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SCASUM = 0.0E0
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IF (N .LE. 0) RETURN
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C
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IF (INCX .EQ. 1) GOTO 20
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C
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C Code for increment not equal to 1.
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C
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IX = 1
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IF (INCX .LT. 0) IX = (-N+1)*INCX + 1
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DO 10 I = 1,N
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SCASUM = SCASUM + ABS(REAL(CX(IX))) + ABS(AIMAG(CX(IX)))
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IX = IX + INCX
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10 CONTINUE
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RETURN
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C
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C Code for increment equal to 1.
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C
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20 DO 30 I = 1,N
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SCASUM = SCASUM + ABS(REAL(CX(I))) + ABS(AIMAG(CX(I)))
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30 CONTINUE
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RETURN
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END
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