Manuel Mall wrote:
What is still unclear to me is if it is worthwhile to implement this
two pass approach, i.e. use INFINITE penalties first and relax later, or if
it is good enough for 99.99% of cases just to start with INFINITE-1
penalties for mandatory keeps?
I think the second pass is necessary, in order to be sure that we are
breaking a keep because there really isn't any other alternative.
Otherwise, I'm sure that for each value < INFINITE we use, we could create
a (contrived) example where the algorithm prefers breaking the keep
instead of using a different, legal (but somewhat uglier) break, such
behaving in a non-conformant way.
Reading again the specs, I even start wondering whether it would really be
right to allow a break between objects tied by a keep constraint:
"Each keep condition must also be satisfied, except when this would cause
a break condition or a stronger keep condition to fail to be satisfied. If
not all of a set of keep conditions of equal strength can be satisfied,
then some maximal satisfiable subset of conditions of that strength must
be satisfied (together with all break conditions and maximal subsets of
stronger keep conditions, if any)."
It seems to me that the prescribed behaviour requires a keep constraint
with force = "always" to be satisfied *always* :-), even if this would
mean having some overflowing content. More than this, even a keep with
force = N could be broken only in order to satisfy a keep with greater
force, and not to avoid an overflow.
I seem to recall that in Knuth's paper the author talks about a symbol he
introduced in tex to represent a space that could be used as a line break
in dire straits, having a penalty value = inf-1 (where inf was the special
finite value representing infinity). Maybe we could similarly add some
"soft-keep" extensions?
Regards
Luca
