[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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[e200b7a] | 4 | ! To be used, if the non-standard Fortran function erf does not exist on |
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| 5 | ! your machine |
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| 6 | ! |
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| 7 | !aus: Numerical Recipes (FORTRAN) / Chapter 6. |
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| 8 | ! |
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| 9 | !6.1 FUNCTION GAMMLN |
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| 10 | !6.2 FUNCTION GAMMP <6.2:GSER/6.2:GCF/6.1:GAMMLN> |
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| 11 | !6.2 FUNCTION GAMMQ <6.2:GSER/6.2:GCF/6.1:GAMMLN> |
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| 12 | !6.2 SUBROUTINE GSER <6.1:GAMMLN> |
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| 13 | !6.2 SUBROUTINE GCF <6.1:GAMMLN> |
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| 14 | !6.2 FUNCTION ERF <6.2:GAMMP/6.2:GSER/6.2:GCF/6.1:GAMMLN> |
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| 15 | !6.2 FUNCTION ERFC <6.2.:GAMMP/6.2:GAMMQ/6.2:GSER/ |
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| 16 | ! 6.2:GCF/6.1:GAMMLN> |
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| 17 | !6.2 FUNCTION ERFCC |
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| 18 | |
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| 19 | function gammln(xx) |
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| 20 | |
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| 21 | use par_mod, only: dp |
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| 22 | |
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| 23 | implicit none |
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| 24 | |
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| 25 | integer :: j |
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| 26 | real :: x,tmp,ser,xx,gammln |
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| 27 | real :: cof(6) = (/ & |
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| 28 | 76.18009173_dp, -86.50532033_dp, 24.01409822_dp, & |
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| 29 | -1.231739516_dp, .120858003e-2_dp, -.536382e-5_dp /) |
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| 30 | real :: stp = 2.50662827465_dp |
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| 31 | real :: half = 0.5_dp, one = 1.0_dp, fpf = 5.5_dp |
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| 32 | |
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| 33 | x=xx-one |
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| 34 | tmp=x+fpf |
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| 35 | tmp=(x+half)*log(tmp)-tmp |
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| 36 | ser=one |
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| 37 | do j=1,6 |
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| 38 | x=x+one |
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| 39 | ser=ser+cof(j)/x |
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| 40 | end do |
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| 41 | gammln=tmp+log(stp*ser) |
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| 42 | end function gammln |
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| 43 | |
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| 44 | function gammp(a,x) |
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| 45 | |
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| 46 | implicit none |
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| 47 | |
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| 48 | real :: a, x, gln, gamser, gammp, gammcf |
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| 49 | |
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| 50 | if(x .lt. 0. .or. a .le. 0.) then |
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| 51 | print*, 'gammp' |
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| 52 | stop |
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| 53 | end if |
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| 54 | if(x.lt.a+1.)then |
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| 55 | call gser(gamser,a,x,gln) |
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| 56 | gammp=gamser |
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| 57 | else |
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| 58 | call gcf(gammcf,a,x,gln) |
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| 59 | gammp=1.-gammcf |
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| 60 | endif |
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| 61 | end function gammp |
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| 62 | |
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| 63 | function gammq(a,x) |
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| 64 | |
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| 65 | implicit none |
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| 66 | |
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| 67 | real :: a, x, gln, gamser, gammq, gammcf |
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| 68 | |
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| 69 | if(x.lt.0..or.a.le.0.) then |
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| 70 | print*, 'gammq' |
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| 71 | stop |
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| 72 | end if |
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| 73 | if(x.lt.a+1.)then |
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| 74 | call gser(gamser,a,x,gln) |
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| 75 | gammq=1.-gamser |
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| 76 | else |
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| 77 | call gcf(gammcf,a,x,gln) |
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| 78 | gammq=gammcf |
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| 79 | endif |
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| 80 | end function gammq |
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| 81 | |
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| 82 | subroutine gser(gamser,a,x,gln) |
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| 83 | |
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| 84 | implicit none |
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| 85 | |
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| 86 | integer :: n |
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| 87 | real :: gamser, a, x, gln, ap, summ, del |
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| 88 | real, external :: gammln |
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| 89 | |
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| 90 | integer,parameter :: itmax=100 |
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| 91 | real,parameter :: eps=3.e-7 |
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| 92 | |
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| 93 | gln=gammln(a) |
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| 94 | if(x.le.0.)then |
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| 95 | if(x.lt.0.) then |
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| 96 | print*, 'gser' |
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| 97 | stop |
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| 98 | end if |
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| 99 | gamser=0. |
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| 100 | return |
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| 101 | endif |
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| 102 | ap=a |
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| 103 | summ=1./a |
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| 104 | del=summ |
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| 105 | do n=1,itmax |
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| 106 | ap=ap+1. |
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| 107 | del=del*x/ap |
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| 108 | summ=summ+del |
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| 109 | if(abs(del).lt.abs(summ)*eps)go to 1 |
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| 110 | end do |
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| 111 | print*, 'gser: a too large, itmax too small' |
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| 112 | stop |
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| 113 | 1 gamser=summ*exp(-x+a*log(x)-gln) |
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| 114 | end subroutine gser |
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| 115 | |
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| 116 | subroutine gcf(gammcf,a,x,gln) |
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| 117 | |
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| 118 | implicit none |
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| 119 | |
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| 120 | integer :: n |
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| 121 | real :: gammcf, a, x, gln, gold, a0, a1, b0, b1, fac, an, anf, ana, g |
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| 122 | real, external :: gammln |
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| 123 | |
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| 124 | integer,parameter :: itmax=100 |
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| 125 | real,parameter :: eps=3.e-7 |
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| 126 | |
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| 127 | gln=gammln(a) |
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| 128 | gold=0. |
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| 129 | a0=1. |
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| 130 | a1=x |
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| 131 | b0=0. |
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| 132 | b1=1. |
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| 133 | fac=1. |
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| 134 | do n=1,itmax |
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| 135 | an=real(n) |
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| 136 | ana=an-a |
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| 137 | a0=(a1+a0*ana)*fac |
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| 138 | b0=(b1+b0*ana)*fac |
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| 139 | anf=an*fac |
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| 140 | a1=x*a0+anf*a1 |
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| 141 | b1=x*b0+anf*b1 |
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| 142 | if(a1.ne.0.)then |
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| 143 | fac=1./a1 |
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| 144 | g=b1*fac |
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| 145 | if(abs((g-gold)/g).lt.eps)go to 1 |
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| 146 | gold=g |
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| 147 | endif |
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| 148 | end do |
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| 149 | print*, 'gcf: a too large, itmax too small' |
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| 150 | stop |
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| 151 | 1 gammcf=exp(-x+a*alog(x)-gln)*g |
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| 152 | end subroutine gcf |
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| 153 | |
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| 154 | function erf(x) |
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| 155 | |
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| 156 | implicit none |
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| 157 | |
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| 158 | real :: x, erf |
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| 159 | real, external :: gammp |
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| 160 | |
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| 161 | if(x.lt.0.)then |
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| 162 | erf=-gammp(.5,x**2) |
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| 163 | else |
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| 164 | erf=gammp(.5,x**2) |
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| 165 | endif |
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| 166 | end function erf |
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| 167 | |
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| 168 | function erfc(x) |
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| 169 | |
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| 170 | implicit none |
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| 171 | |
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| 172 | real :: x, erfc |
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| 173 | real, external :: gammp, gammq |
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| 174 | |
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| 175 | if(x.lt.0.)then |
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| 176 | erfc=1.+gammp(.5,x**2) |
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| 177 | else |
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| 178 | erfc=gammq(.5,x**2) |
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| 179 | endif |
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| 180 | end function erfc |
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| 181 | |
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| 182 | function erfcc(x) |
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| 183 | |
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| 184 | implicit none |
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| 185 | |
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| 186 | real :: x, z, t, erfcc |
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| 187 | |
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| 188 | z=abs(x) |
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| 189 | t=1./(1.+0.5*z) |
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| 190 | erfcc=t*exp(-z*z-1.26551223+t*(1.00002368+t*(.37409196+ & |
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| 191 | t*(.09678418+t*(-.18628806+t*(.27886807+t*(-1.13520398+ & |
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| 192 | t*(1.48851587+t*(-.82215223+t*.17087277))))))))) |
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| 193 | if (x.lt.0.) erfcc=2.-erfcc |
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| 194 | end function erfcc |
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