forked from lijiext/lammps
59 lines
1.3 KiB
Fortran
59 lines
1.3 KiB
Fortran
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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* IDAMAX finds the index of element having max. absolute value.
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*
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* Further Details
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* ===============
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*
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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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*
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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
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