appendU is strict, insertWith just doesn't force it (follow the source link in the haddocks to see why).
Ok, I see. But, IMHO, this should be clearly documented.
There seems to be some agreement that strict variant operations should also be provided, but it needs some more thinking, and whenever I look at the code, I have the feeling that there are just too many operations defined in it, so I look away again:-(
However, reading the code now, I prefer my version using alter.
Yes, it is a more direct way to enforce strict evaluation. Btw, if your update function 'f' is strict in 'old' and 'new', you might just want to use 'Just $! f old new' and save all those 'seq's.
By the way, about insertWith/alter; from IntMap documentation:
insertWithKey: O(min(n,W) alter: O(log n)
So, alter is more efficient than insertWithKey? And what is that `W` ?
'W' is a maximum bound (see comment at top of that haddock page). 'alter' has some shortcuts if the update functions doesn't actually do anything, but for reimplementing 'insertWithKey', the complexity should be the same as the code would be the same.
But piling up appendUs is still not a good idea. For a moment, I thought that the stream representation's (+++) was handling runtime fusion gracefully, but a simple test case suggests otherwise at least for the simpler case of consU (the attached appendU.hs doesn't do any appendUs, as the consU case already demonstrates the issue; be careful with large numbers here, it'll quickly eat your ram):
I'm not sure to fully understand the code.
Writing ':<' for 'snocU', the code for 'singletonU a1: But, again, IMHO it does not apply to my original problem. It is a question of resource constraints, probably. Instead of maintaining
an 'IntMap (UArr Int)' all the way through buildup, you could use an
'IntMap [Int]' while parsing, and then compress into 'IntMap (UArr Int)'
when parsing is finished. If you can afford the larger memory profile
during parsing, this should give better overall performance, with the
same memory need for the final state, but larger memory needs up
to that state. I'd be interested in the differences, if you try it.
Claus