[mercury-users] First solution in csharp without try/catch

Paul Bone pbone at csse.unimelb.edu.au
Tue Jan 17 14:20:32 AEDT 2012

On Tue, Jan 17, 2012 at 02:14:20PM +1100, Paul Bone wrote:
> On Sat, Jan 14, 2012 at 09:03:08AM -0800, Jeff Thompson wrote:
> > 
> > As above, the times for Mercury code are 0.45 seconds for the
> > baseline and 171 seconds if it commits.  For the "yield" code it is
> > 2.33 seconds for the baseline and 2.03 if it commits after one
> > solution.  As expected, since the "yield" code uses the same
> > infrastructure in both cases, it takes less time to search less
> > solutions.  But the baseline Mercury code is faster than the "yield"
> > code which allocates an iterator object on the heap for every
> > "foreach" loop (as opposed to Mercury's more efficient approach of
> > using continuations).
> > 
> > 
> > 	X > 2 	X > 0
> > Mercury 11.07 	0.45 	171
> > "yield" 	2.33 	2.03
> > 
> What you have to consider is how often you commit to the first solution and how
> often you have a nondet search that does not commit to the first solution (or
> that takes a _long_ time to find the first solution).
> Because commit happens once you only have to pay for try/catch once, but when
> using yield we have to pay for it often (once per node in the search tree).  In
> a nontrivial example this cost will dominate.  Meanwhile, as the size of the
> search space grows the importance of the one-time cost of try/catch will become
> less and less important.

Additionally, if your search is so simple (such as the examples you've used);
then try/catch will be the dominant cost.  However, unless you're doing 10,000
searches in quick succession you won't notice.

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