Comment 7 for bug 707064

> 1. is_net_fully_connected() is recursive, not iterative. Since C doesn't
> optimise tail calls, it means that on designs using very complex nets we
> might see stack exhaustion.

Even if rewritten to be iterative, we would have to maintain a stack
of visited net segments ourselves - in addition to a hash the current
version uses. This might give us better control over memory usage and we
could fail gracefully when allocation fails - but will likely complicate
the function. Is gschem even run on systems where stack does not grow
automatically?

> 2. is_net_fully_connected() treats a netname attribute as a connection,
> but that's not reflected in the doxygen comments.

The Doxygen comment in is_net_fully_connected() says:

    Net is fully connected when it connects at least two separate
    entities. "netname" attribute being attached to one of the net
    segments counts as an connected entity as well.

Any suggestions how to reword this to make it more clear?

> 3. We allocate and build a hashtable for each and every net object in
> the entire design, every time we draw, which is rather expensive. Is
> there any way of optimising things so that the "fully connected" flag is
> only updated when a user modifies the design?

That is on a TODO list - we would have to keep "fully connected" cached
flag in the net objects, or maintain a separate cache of precomputed
values per net segment. The latter would not require making changes to
libgeda, as this is a feature only gschem would make use of. It seems
the most difficult part is to catch all cases where the cache should be
updated.

Any suggestions on the caching approach?