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subroutine ta2lpd(tail,head,ma,n,lp,la,ls)
c
c ta2lpd computes the adjacency vectors lp, la and ls
c from vectors tail and head for a directed graph
c NO CHECKING IS MADE on tail, head and n
c input: tail(ma) = tail nodes
c head(ma) = head nodes
c ma = number of edges
c n = number of nodes
c output: lp(n+1) = pointer vector
c la(ma) = vector of arcs
c ls(ma) = vector of corresponding head nodes
c
integer tail(ma),head(ma),ma,n
integer lp(*),la(ma),ls(ma)
c
integer iarc,inode
c
c first computation of lp
c lp(i+1) = number of tail nodes
c = number of arcs with tail node i+1
c
do 1,inode=1,n+1
lp(inode)=0
1 continue
do 2,iarc=1,ma
lp(tail(iarc)+1)=lp(tail(iarc)+1)+1
2 continue
c
c second computation of lp
c lp(i) = pointer to the first arc
c with tail i in sorted tail
c
lp(1)=1
do 3,inode=2,n
lp(inode)=lp(inode-1)+lp(inode)
3 continue
c
c computation of la and ls
c
do 4,iarc=1,ma
inode=tail(iarc)
la(lp(inode))=iarc
ls(lp(inode))=head(iarc)
lp(inode)=lp(inode)+1
4 continue
c
c last computation of lp
c
do 5,inode=n,1,-1
lp(inode+1)=lp(inode)
5 continue
lp(1)=1
end
c
subroutine ta2lpu(tail,head,ma,n,lp,la,ls)
c
c ta2lpu computes the adjacency vectors lp, la and ls
c from vectors tail and head for an undirected graph
c NO CHECKING IS MADE on tail, head and n
c input: tail(ma) = tail nodes
c head(ma) = head nodes
c ma = number of edges
c n = number of nodes
c output: lp(n+1) = pointer vector
c la(m) = vector of arcs (m=2*ma)
c ls(m) = vector of corresponding head nodes
c
integer tail(ma),head(ma),ma,n
integer lp(*),la(*),ls(*)
c
integer iarc,inode
c
c first computation of lp
c lp(i+1) = number of tail nodes
c = number of arcs with tail node i+1
c
do 1,inode=1,n+1
lp(inode)=0
1 continue
do 2,iarc=1,ma
lp(tail(iarc)+1)=lp(tail(iarc)+1)+1
lp(head(iarc)+1)=lp(head(iarc)+1)+1
2 continue
c
c second computation of lp
c lp(i) = pointer to the first arc
c with tail i in sorted (tail,head)
c
lp(1)=1
do 3,inode=2,n
lp(inode)=lp(inode-1)+lp(inode)
3 continue
c
c computation of la and ls
c
do 4,iarc=1,ma
inode=tail(iarc)
la(lp(inode))=iarc
ls(lp(inode))=head(iarc)
lp(inode)=lp(inode)+1
inode=head(iarc)
la(lp(inode))=iarc
ls(lp(inode))=tail(iarc)
lp(inode)=lp(inode)+1
4 continue
c
c last computation of lp
c
do 5,inode=n,1,-1
lp(inode+1)=lp(inode)
5 continue
lp(1)=1
end
c
subroutine lp2tad(lp,la,ls,n,tail,head)
c
c lp2tad computes the vectors tail and head
c from the adjacency vectors lp, la and ls
c for a directed graph
c NO CHECKING IS MADE on lp, la, ls and n
c input: lp(n+1) = pointer vector
c la(ma) = vector of arcs
c ls(ma) = vector of corresponding head nodes
c n = number of nodes
c output: tail(ma) = tail nodes
c head(ma) = head nodes
c
integer lp(*),la(*),ls(*),n
integer tail(*),head(*)
c
do 1 inod=1,n
do 2 ip=lp(inod),lp(inod+1)-1
tail(la(ip))=inod
head(la(ip))=ls(ip)
2 continue
1 continue
end
c
subroutine lp2tau(lp,la,ls,n,tail,head)
c
c lp2tad computes the vectors tail and head
c from the adjacency vectors lp, la and ls
c for an undirected graph
c NO CHECKING IS MADE on lp, la, ls and n
c input: lp(n+1) = pointer vector
c la(ma) = vector of arcs
c ls(ma) = vector of corresponding head nodes
c n = number of nodes
c output: tail(ma) = tail nodes
c head(ma) = head nodes
c
c
integer lp(*),la(*),ls(*),n
integer tail(*),head(*)
c
integer iarc
c
do 1,inod=1,n
do 2,ip=lp(inod),lp(inod+1)-1
iarc=(la(ip)+1)/2
tail(iarc)=inod
head(iarc)=ls(ip)
2 continue
1 continue
end
c
subroutine findiso(tail,head,ma,n,v)
c
c findiso finds isolated nodes from tail and head description
c of a graph
c NO CHECKING IS MADE on tail, head and n
c input: tail(ma) = tail nodes
c head(ma) = head nodes
c ma = number of edges
c n = number of nodes
c output: v(n) = vector of isolated nodes v(i)=1 is i
c is the number of an isolated node, 0
c otherwise
c
integer tail(ma),head(ma),ma,n,v(n)
c
integer iarc,inode
c
do 1,inode=1,n
v(inode)=0
1 continue
do 2,iarc=1,ma
v(tail(iarc))=1
v(head(iarc))=1
2 continue
end
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