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program random_graph |
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! |
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! It builds a random graph a la Erdoes-Renyi: the probability |
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! that there is an edge between any pair of vertices is p |
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! |
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! * degree is the array which stores the degree of each node, |
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! which is printed out at the end in the file "degree.dat" |
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implicit none |
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integer*8 ibm |
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integer i,j,k,n_edges,iter,n_vert,n_edges_true,denom,denom0,k0 |
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real*8 r,p |
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character*60 sn_vert,sp,sibm |
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character*25,allocatable,dimension(:):: attrN |
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character*(25) addquotes |
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! Reading of input parameters |
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call GETARG(2,sn_vert) |
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call GETARG(4,sp) |
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call GETARG(6,sibm) |
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read(sn_vert,*)n_vert |
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read(sp,*)p |
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read(sibm,*)ibm |
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! Array allocations |
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! Opening of the file where the edges will be saved |
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allocate(attrN(1:n_vert)) |
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denom=1000000000 |
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do i=1,n_vert |
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write(attrN(i),*) i |
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attrN(i) = addquotes(attrN(i)) |
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enddo |
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open(21,file='network.nwb',status='unknown') |
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write(21,108)'# Erdoes-Renyi graph' |
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write(21,110)'# Linking probability ',p |
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write(21,103)'*Nodes ',n_vert |
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write(21,120)'id*int label*string' |
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do i=1,n_vert |
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write(21,*)i,attrN(i) |
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enddo |
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write(21,109)'*UndirectedEdges' |
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write(21,121)'source*int target*int' |
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! The average degree of the graph is given by the product of the |
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! linking probability p and the number of nodes n_vert |
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do i=1,n_vert |
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do j=1,i-1 |
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ibm=ibm*16807 ! Here we create a random number |
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r=0.25d0*(ibm/2147483648.0d0/2147483648.0d0+2.0d0) ! r between 0 and 1 |
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if(r<p)then |
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write(21,*)i,j |
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endif |
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enddo |
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enddo |
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close(21) |
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101 format(i10,8x,i10) |
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102 format(a34,i10) |
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103 format(a6,i10) |
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104 format(i10,9x,e15.6) |
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105 format(4x,e15.6,4x,e15.6) |
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108 format(a21) |
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109 format(a16) |
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110 format(a22,e15.6) |
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120 format(a24) |
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121 format(a26) |
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stop |
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end program random_graph |
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character*(25) function addquotes(value) |
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character*(*) value |
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character*22 longname |
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if(len(TRIM(ADJUSTL(value))) >= 23) then |
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longname = ADJUSTL(value) |
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addquotes = '"' // longname // '"' |
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else |
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addquotes = '"' // TRIM(ADJUSTL(value)) // '"' |
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endif |
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return |
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end |
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