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subroutine isova0(a,lda,m,n,path,kpath,ir,ic,dir,pend,
c Copyright INRIA
$ h,v,c)
c% but
c Sous programme appele par le sous programme isoval
c%
double precision a(lda,*),c,path(2,*)
integer lda,m,n,h(m,*),v(m-1,*)
c
logical pend
integer north,south,east,west,dir
data north/0/,south/1/,east/2/,west/3/
c extend the path at this level by one edge element
if(dir.eq.north) then
if(v(ir,ic).lt.0) then
if(kpath.gt.1) h(ir,ic)=0
c path to east
goto 30
else if(v(ir,ic+1).lt.0) then
if(kpath.gt.1) h(ir,ic)=0
c path to west
goto 40
else if(h(ir+1,ic).lt.0) then
if(kpath.gt.1) h(ir,ic)=0
c path to north
goto 10
else
pend=.true.
endif
else if(dir.eq.west) then
if(h(ir+1,ic).lt.0) then
if(kpath.gt.1) v(ir,ic)=0
c path to north
goto 10
else if(h(ir,ic).lt.0) then
if(kpath.gt.1) v(ir,ic)=0
c path to south
goto 20
else if(v(ir,ic+1).lt.0) then
if(kpath.gt.1) v(ir,ic)=0
c path to west
goto 40
else
pend=.true.
endif
else if( dir.eq.south) then
if(v(ir,ic+1).lt.0) then
if(kpath.gt.1) h(ir+1,ic)=0
c path to west
goto 40
else if(v(ir,ic).lt.0) then
if(kpath.gt.1) h(ir+1,ic)=0
c path to east
goto 30
else if(h(ir,ic).lt.0) then
if(kpath.gt.1) h(ir+1,ic)=0
c path to south
goto 20
else
pend=.true.
endif
else if(dir.eq.east) then
if(h(ir,ic).lt.0) then
if(kpath.gt.1) v(ir,ic+1)=0
c path to south
goto 20
else if(h(ir+1,ic).lt.0) then
if(kpath.gt.1) v(ir,ic+1)=0
c path to north
goto 10
else if(v(ir,ic).lt.0) then
if(kpath.gt.1) v(ir,ic+1)=0
c path to east
goto 30
else
pend=.true.
endif
endif
return
c
10 continue
c
c NORTH
c
kpath=kpath+1
path(2,kpath)=ir+1
path(1,kpath)=ic+(c-a(ir+1,ic))/(a(ir+1,ic+1)-a(ir+1,ic))
if(ir+1.lt.m) then
ir=ir+1
dir=north
else
pend=.true.
endif
return
20 continue
c
c SOUTH
c
kpath=kpath+1
path(2,kpath)=ir
path(1,kpath)=ic+(c-a(ir,ic))/(a(ir,ic+1)-a(ir,ic))
if(ir.gt.1) then
ir=ir-1
dir=south
else
pend=.true.
endif
return
c
30 continue
c
c EAST
c
kpath=kpath+1
path(2,kpath)=ir+(c-a(ir,ic))/(a(ir+1,ic)-a(ir,ic))
path(1,kpath)=ic
if(ic.gt.1) then
ic=ic-1
dir=east
else
pend=.true.
endif
return
c
40 continue
c
c WEST
c
kpath=kpath+1
path(2,kpath)=ir+(c-a(ir,ic+1))/(a(ir+1,ic+1)-a(ir,ic+1))
path(1,kpath)=ic+1
if(ic+1.lt.n) then
ic=ic+1
dir=west
else
pend=.true.
endif
return
c
end
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