[92fab65] | 1 | ! SPDX-FileCopyrightText: FLEXPART 1998-2019, see flexpart_license.txt |
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| 2 | ! SPDX-License-Identifier: GPL-3.0-or-later |
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[332fbbd] | 3 | |
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[8a65cb0] | 4 | ! Taken from Press et al., Numerical Recipes |
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| 5 | |
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| 6 | module random_mod |
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| 7 | |
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| 8 | implicit none |
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| 9 | |
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| 10 | contains |
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| 11 | |
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| 12 | function ran1(idum) |
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| 13 | |
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| 14 | implicit none |
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| 15 | |
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| 16 | integer :: idum |
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| 17 | real :: ran1 |
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| 18 | integer,parameter :: ia=16807, im=2147483647, iq=127773, ir=2836 |
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| 19 | integer,parameter :: ntab=32, ndiv=1+(im-1)/ntab |
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| 20 | real,parameter :: am=1./im, eps=1.2e-7, rnmx=1.-eps |
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| 21 | integer :: j, k |
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| 22 | integer :: iv(ntab) = (/ (0,j=1,ntab) /) |
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| 23 | integer :: iy=0 |
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| 24 | |
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| 25 | if (idum.le.0.or.iy.eq.0) then |
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| 26 | idum=max(-idum,1) |
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| 27 | do j=ntab+8,1,-1 |
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| 28 | k=idum/iq |
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| 29 | idum=ia*(idum-k*iq)-ir*k |
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| 30 | if (idum.lt.0) idum=idum+im |
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| 31 | if (j.le.ntab) iv(j)=idum |
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| 32 | enddo |
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| 33 | iy=iv(1) |
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| 34 | endif |
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| 35 | k=idum/iq |
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| 36 | idum=ia*(idum-k*iq)-ir*k |
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| 37 | if (idum.lt.0) idum=idum+im |
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| 38 | j=1+iy/ndiv |
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| 39 | iy=iv(j) |
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| 40 | iv(j)=idum |
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| 41 | ran1=min(am*iy,rnmx) |
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| 42 | end function ran1 |
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| 43 | |
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| 44 | |
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| 45 | function gasdev(idum) |
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| 46 | |
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| 47 | implicit none |
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| 48 | |
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| 49 | integer :: idum |
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| 50 | real :: gasdev, fac, r, v1, v2 |
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| 51 | integer :: iset = 0 |
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| 52 | real :: gset = 0. |
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| 53 | |
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| 54 | if (iset.eq.0) then |
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| 55 | 1 v1=2.*ran3(idum)-1. |
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| 56 | v2=2.*ran3(idum)-1. |
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| 57 | r=v1**2+v2**2 |
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| 58 | if(r.ge.1.0 .or. r.eq.0.0) go to 1 |
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| 59 | fac=sqrt(-2.*log(r)/r) |
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| 60 | gset=v1*fac |
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| 61 | gasdev=v2*fac |
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| 62 | iset=1 |
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| 63 | else |
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| 64 | gasdev=gset |
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| 65 | iset=0 |
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| 66 | endif |
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| 67 | end function gasdev |
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| 68 | |
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| 69 | |
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| 70 | subroutine gasdev1(idum,random1,random2) |
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| 71 | |
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| 72 | implicit none |
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| 73 | |
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| 74 | integer :: idum |
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| 75 | real :: random1, random2, fac, v1, v2, r |
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| 76 | |
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| 77 | 1 v1=2.*ran3(idum)-1. |
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| 78 | v2=2.*ran3(idum)-1. |
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| 79 | r=v1**2+v2**2 |
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| 80 | if(r.ge.1.0 .or. r.eq.0.0) go to 1 |
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| 81 | fac=sqrt(-2.*log(r)/r) |
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| 82 | random1=v1*fac |
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| 83 | random2=v2*fac |
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| 84 | ! Limit the random numbers to lie within the interval -3 and +3 |
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| 85 | !************************************************************** |
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| 86 | if (random1.lt.-3.) random1=-3. |
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| 87 | if (random2.lt.-3.) random2=-3. |
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| 88 | if (random1.gt.3.) random1=3. |
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| 89 | if (random2.gt.3.) random2=3. |
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| 90 | end subroutine gasdev1 |
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| 91 | |
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| 92 | |
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| 93 | function ran3(idum) |
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| 94 | |
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| 95 | implicit none |
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| 96 | |
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| 97 | integer :: idum |
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| 98 | real :: ran3 |
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| 99 | |
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| 100 | integer,parameter :: mbig=1000000000, mseed=161803398, mz=0 |
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| 101 | real,parameter :: fac=1./mbig |
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| 102 | integer :: i,ii,inext,inextp,k |
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| 103 | integer :: mj,mk,ma(55) |
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| 104 | |
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| 105 | save inext,inextp,ma |
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| 106 | integer :: iff = 0 |
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| 107 | |
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| 108 | if(idum.lt.0.or.iff.eq.0)then |
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| 109 | iff=1 |
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| 110 | mj=mseed-iabs(idum) |
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| 111 | mj=mod(mj,mbig) |
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| 112 | ma(55)=mj |
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| 113 | mk=1 |
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| 114 | do i=1,54 |
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| 115 | ii=mod(21*i,55) |
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| 116 | ma(ii)=mk |
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| 117 | mk=mj-mk |
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| 118 | if(mk.lt.mz)mk=mk+mbig |
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| 119 | mj=ma(ii) |
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| 120 | end do |
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| 121 | do k=1,4 |
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| 122 | do i=1,55 |
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| 123 | ma(i)=ma(i)-ma(1+mod(i+30,55)) |
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| 124 | if(ma(i).lt.mz)ma(i)=ma(i)+mbig |
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| 125 | end do |
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| 126 | end do |
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| 127 | inext=0 |
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| 128 | inextp=31 |
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| 129 | idum=1 |
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| 130 | endif |
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| 131 | inext=inext+1 |
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| 132 | if(inext.eq.56)inext=1 |
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| 133 | inextp=inextp+1 |
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| 134 | if(inextp.eq.56)inextp=1 |
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| 135 | mj=ma(inext)-ma(inextp) |
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| 136 | if(mj.lt.mz)mj=mj+mbig |
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| 137 | ma(inext)=mj |
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| 138 | ran3=mj*fac |
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| 139 | end function ran3 |
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| 140 | ! (C) Copr. 1986-92 Numerical Recipes Software US. |
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| 141 | |
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| 142 | end module random_mod |
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