Small update on the 'modular decomposition story'.
Today I ran valgrind on the code, and ended up finding where the error
comes from. Around line 972 of dm.c, one can find:
for(v = n-1; v>=0; v--)
if(ds[v-1] != -1){
L2[v]=v;
while( pile[sommet] < ds[v-1])
L2[pile[sommet--]]=v;
}
Now, because v can be equal to 0 in the loop, ds[v-1] is actually
ds[-1] and leads, unsurprisingly, to a wrong area of the memory.
Valgrind reports it like that:
==23980== 1 errors in context 3 of 4:
==23980== Invalid read of size 4
==23980== at 0x40269D: algo2 (dm.c:972)
Thus it is rather obvious where the error comes from (there are some
other occurrences of the same problem). I was about to write an email
to the authors, when I noticed that..... I had already sent an email
with the very same information, i.e. line number+explanation+short
tutorial on valgrind, and that was... one year ago. On the 6th of
April 2014, to be specific.
So that is not a problem of having to debug under mac OS X.
Nathann
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