with(coxeter):
read maxset;
read chrome;

# Find colorings for the H4 graph.
# Select good inner products (assuming r1<>r2);

gip:=proc(i,j,pr) local c;
  c:=iprod(pr[i],pr[j]);
  if c<EPS and abs(c+4/g)>EPS then {i,j} fi;
end:

R:=H4;
interface(quiet=true);
pr:=pos_roots(R): g:=-iprod(pr[1],pr[2]): EPS:=.001:
X:={$1..nops(pr)}:
G:={seq(seq(gip(j,i,pr),j=1..i-1),i=1..nops(pr))}: nops(G);
mis:=maxset(G,X): nops(mis);
st:=time(): k0:=5: chrome(mis,X,5,'c'), c, .733*(time()-st);
st:=time(): k0:=7: chrome(mis,X,6,'c'), c, .733*(time()-st);
interface(quiet=false);
quit;