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| 1 | INTEGER FUNCTION IDAMAX(N,DX,INCX) |
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| 2 | * .. Scalar Arguments .. |
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| 3 | INTEGER INCX,N |
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| 4 | * .. |
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| 5 | * .. Array Arguments .. |
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| 6 | DOUBLE PRECISION DX(*) |
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| 7 | * .. |
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| 8 | * |
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| 9 | * Purpose |
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| 10 | * ======= |
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| 11 | * |
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| 12 | * finds the index of element having max. absolute value. |
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| 13 | * jack dongarra, linpack, 3/11/78. |
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| 14 | * modified 3/93 to return if incx .le. 0. |
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| 15 | * modified 12/3/93, array(1) declarations changed to array(*) |
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| 16 | * |
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| 17 | * |
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| 18 | * .. Local Scalars .. |
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| 19 | DOUBLE PRECISION DMAX |
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| 20 | INTEGER I,IX |
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| 21 | * .. |
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| 22 | * .. Intrinsic Functions .. |
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| 23 | INTRINSIC DABS |
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| 24 | * .. |
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| 25 | IDAMAX = 0 |
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| 26 | IF (N.LT.1 .OR. INCX.LE.0) RETURN |
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| 27 | IDAMAX = 1 |
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| 28 | IF (N.EQ.1) RETURN |
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| 29 | IF (INCX.EQ.1) GO TO 20 |
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| 30 | * |
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| 31 | * code for increment not equal to 1 |
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| 32 | * |
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| 33 | IX = 1 |
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| 34 | DMAX = DABS(DX(1)) |
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| 35 | IX = IX + INCX |
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| 36 | DO 10 I = 2,N |
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| 37 | IF (DABS(DX(IX)).LE.DMAX) GO TO 5 |
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| 38 | IDAMAX = I |
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| 39 | DMAX = DABS(DX(IX)) |
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| 40 | 5 IX = IX + INCX |
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| 41 | 10 CONTINUE |
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| 42 | RETURN |
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| 43 | * |
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| 44 | * code for increment equal to 1 |
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| 45 | * |
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| 46 | 20 DMAX = DABS(DX(1)) |
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| 47 | DO 30 I = 2,N |
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| 48 | IF (DABS(DX(I)).LE.DMAX) GO TO 30 |
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| 49 | IDAMAX = I |
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| 50 | DMAX = DABS(DX(I)) |
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| 51 | 30 CONTINUE |
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| 52 | RETURN |
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| 53 | END |
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