root / src / blas / izamax.f @ 2
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| 1 | 1 | equemene | INTEGER FUNCTION IZAMAX(N,ZX,INCX) |
|---|---|---|---|
| 2 | 1 | equemene | * .. Scalar Arguments .. |
| 3 | 1 | equemene | INTEGER INCX,N |
| 4 | 1 | equemene | * .. |
| 5 | 1 | equemene | * .. Array Arguments .. |
| 6 | 1 | equemene | DOUBLE COMPLEX ZX(*) |
| 7 | 1 | equemene | * .. |
| 8 | 1 | equemene | * |
| 9 | 1 | equemene | * Purpose |
| 10 | 1 | equemene | * ======= |
| 11 | 1 | equemene | * |
| 12 | 1 | equemene | * finds the index of element having max. absolute value. |
| 13 | 1 | equemene | * jack dongarra, 1/15/85. |
| 14 | 1 | equemene | * modified 3/93 to return if incx .le. 0. |
| 15 | 1 | equemene | * modified 12/3/93, array(1) declarations changed to array(*) |
| 16 | 1 | equemene | * |
| 17 | 1 | equemene | * |
| 18 | 1 | equemene | * .. Local Scalars .. |
| 19 | 1 | equemene | DOUBLE PRECISION SMAX |
| 20 | 1 | equemene | INTEGER I,IX |
| 21 | 1 | equemene | * .. |
| 22 | 1 | equemene | * .. External Functions .. |
| 23 | 1 | equemene | DOUBLE PRECISION DCABS1 |
| 24 | 1 | equemene | EXTERNAL DCABS1 |
| 25 | 1 | equemene | * .. |
| 26 | 1 | equemene | IZAMAX = 0 |
| 27 | 1 | equemene | IF (N.LT.1 .OR. INCX.LE.0) RETURN |
| 28 | 1 | equemene | IZAMAX = 1 |
| 29 | 1 | equemene | IF (N.EQ.1) RETURN |
| 30 | 1 | equemene | IF (INCX.EQ.1) GO TO 20 |
| 31 | 1 | equemene | * |
| 32 | 1 | equemene | * code for increment not equal to 1 |
| 33 | 1 | equemene | * |
| 34 | 1 | equemene | IX = 1 |
| 35 | 1 | equemene | SMAX = DCABS1(ZX(1)) |
| 36 | 1 | equemene | IX = IX + INCX |
| 37 | 1 | equemene | DO 10 I = 2,N |
| 38 | 1 | equemene | IF (DCABS1(ZX(IX)).LE.SMAX) GO TO 5 |
| 39 | 1 | equemene | IZAMAX = I |
| 40 | 1 | equemene | SMAX = DCABS1(ZX(IX)) |
| 41 | 1 | equemene | 5 IX = IX + INCX |
| 42 | 1 | equemene | 10 CONTINUE |
| 43 | 1 | equemene | RETURN |
| 44 | 1 | equemene | * |
| 45 | 1 | equemene | * code for increment equal to 1 |
| 46 | 1 | equemene | * |
| 47 | 1 | equemene | 20 SMAX = DCABS1(ZX(1)) |
| 48 | 1 | equemene | DO 30 I = 2,N |
| 49 | 1 | equemene | IF (DCABS1(ZX(I)).LE.SMAX) GO TO 30 |
| 50 | 1 | equemene | IZAMAX = I |
| 51 | 1 | equemene | SMAX = DCABS1(ZX(I)) |
| 52 | 1 | equemene | 30 CONTINUE |
| 53 | 1 | equemene | RETURN |
| 54 | 1 | equemene | END |