SWDOT/DWDOT/CWDOTC/CWDOTU/ZWDOTC/ZWDOTU | Weighted dot product | ||||
| incy | Increment for the array y: | |||
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| incy ≥ 0 | y is stored forward in array y; that is, | ||
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| yi is stored in y((i−1)⋅incy+1). |
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| incy < 0 | y is stored backward in array y; that | ||
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| is, yi is stored in y((i−n)⋅incy+1). |
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| Use incy = 1 if the vector y is stored contiguously in | |||
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| array y; that is, if yi is stored in y(i). Refer to “BLAS | |||
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| Indexing Conventions” in the introduction to this | |||
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| chapter. |
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Output | s | The resulting value of the weighted dot product. If | |||
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| n ≤ 0, then s = 0. Otherwise, | |||
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| n |
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| s = ∑ wi xi yi |
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| i = 1 |
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| unless the subprogram name is CWDOTC or | |||
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| ZWDOTC, in which case | |||
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| n |
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| s = ∑ wi | x | i yi. |
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| i = 1 |
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Notes | If incw = 0, then wi | = w(1) for all i. If incx = 0, then xi = x(1) for all i. If | |||
| incy = 0, then yi = y(1) for all i. In any of these cases, another VECLIB dot | ||||
| product subprogram would be more efficient. | ||||
Fortran | REAL*4 FUNCTION SWDOT (N, W,INCW, X,INCX, Y,INCY) | ||||
Equivalent | REAL*4 W(*),X(*),Y(*) |
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SWDOT = 0.0
IF ( N .LE. 0 ) RETURN IW = 1
IX = 1
IY = 1
IF ( INCW .LT. 0 ) IW = 1 -
SWDOT = SWDOT + W(IW) * X(IX) * Y(IY) IW = IW + INCW
IX = IX + INCX
IY = IY + INCY 10 CONTINUE
RETURN END
148HP MLIB User’s Guide