root / src / blas / zaxpy.f @ 7
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SUBROUTINE ZAXPY(N,ZA,ZX,INCX,ZY,INCY) |
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* .. Scalar Arguments .. |
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DOUBLE COMPLEX ZA |
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INTEGER INCX,INCY,N |
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* .. |
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* .. Array Arguments .. |
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DOUBLE COMPLEX ZX(*),ZY(*) |
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* .. |
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* |
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* Purpose |
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* ======= |
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* |
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* constant times a vector plus a vector. |
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* jack dongarra, 3/11/78. |
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* modified 12/3/93, array(1) declarations changed to array(*) |
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* |
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|
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* .. Local Scalars .. |
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INTEGER I,IX,IY |
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* .. |
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* .. External Functions .. |
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DOUBLE PRECISION DCABS1 |
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EXTERNAL DCABS1 |
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* .. |
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IF (N.LE.0) RETURN |
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IF (DCABS1(ZA).EQ.0.0d0) RETURN |
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IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20 |
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* |
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* code for unequal increments or equal increments |
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* not equal to 1 |
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* |
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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 10 I = 1,N |
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ZY(IY) = ZY(IY) + ZA*ZX(IX) |
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IX = IX + INCX |
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IY = IY + INCY |
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10 CONTINUE |
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RETURN |
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* |
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* code for both increments equal to 1 |
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* |
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20 DO 30 I = 1,N |
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ZY(I) = ZY(I) + ZA*ZX(I) |
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30 CONTINUE |
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RETURN |
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END |