> > I'm trying to run a piece of software that uses FLTK so I've build
> FLTK
> > from scratch and the other software from scratch and it compiles with
> no
> > errors. When I try to run it, it fires up ok unti l start trying to
> > interact with the FLTK based GUI, at which point it locks up. I've
> > occasionally seen it do a repaint if I leave it for 10 minutes or so.
> 
> That's weird.
> 
> > The exact same binaries work fine on a physical machine when I've
> copied
> > them over to try them out.
> 
> So the binaries seem to be okay.


Oh! 
Now, that just reminded me... (Caution: Probably pointless anecdote coming up!)

I did once see something that might be similar. Maybe...

Questions: How many CPU cores does the VM have? How many cores does the "real" machine you tested on have?

The reason I'm asking is that I once had to help debug a bit of code that "ran perfectly" on a real machine, where it had been developed, but would not work at all well on a VM, where it was deployed.

So it turned out that the key was that the "real" machine had 2 HT cores (so looked like 4 cores to the OS) whereas the VM was a single core machine.

This mattered because the code was multi-threaded and *quite badly written* and some of the many, many, child threads were spinning, and never blocking or yielding.

On the multi-core CPU that just pegged some of the CPU's, but the rest of the program continued running on the other CPU's and "all was well".

On the VM, the "bad threads" pegged the single CPU and made the rest of the program run *really badly* - though it did still run, albeit slowly. Not 10-mins slowly, mind you, but much slower that it ought to.

Once we fixed the bad threads, all was well.

Of course, if your code is not threaded at all, this is unlikely to be a useful story...




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