root / src / blas / idamax.f @ 10
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INTEGER FUNCTION IDAMAX(N,DX,INCX) |
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* .. Scalar Arguments .. |
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INTEGER INCX,N |
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* .. |
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* .. Array Arguments .. |
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DOUBLE PRECISION DX(*) |
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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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* finds the index of element having max. absolute value. |
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* jack dongarra, linpack, 3/11/78. |
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* modified 3/93 to return if incx .le. 0. |
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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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DOUBLE PRECISION DMAX |
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INTEGER I,IX |
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* .. |
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* .. Intrinsic Functions .. |
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INTRINSIC DABS |
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* .. |
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IDAMAX = 0 |
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IF (N.LT.1 .OR. INCX.LE.0) RETURN |
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IDAMAX = 1 |
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IF (N.EQ.1) RETURN |
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IF (INCX.EQ.1) GO TO 20 |
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* |
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* code for increment not equal to 1 |
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* |
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IX = 1 |
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DMAX = DABS(DX(1)) |
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IX = IX + INCX |
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DO 10 I = 2,N |
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IF (DABS(DX(IX)).LE.DMAX) GO TO 5 |
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IDAMAX = I |
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DMAX = DABS(DX(IX)) |
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5 IX = IX + INCX |
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10 CONTINUE |
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RETURN |
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* |
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* code for increment equal to 1 |
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* |
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20 DMAX = DABS(DX(1)) |
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DO 30 I = 2,N |
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IF (DABS(DX(I)).LE.DMAX) GO TO 30 |
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IDAMAX = I |
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DMAX = DABS(DX(I)) |
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30 CONTINUE |
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RETURN |
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END |