[m-dev.] tabling, trailing and impure references

David Overton dmo at cs.mu.OZ.AU
Thu Aug 7 09:43:10 AEST 2003


On Mon, Aug 04, 2003 at 02:28:16PM +1000, Zoltan Somogyi wrote:
> On 04-Aug-2003, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> > > Question 2:	The reference manual says: "if you enable the use of
> > > 		trailing ... then any use of tabling will result in a
> > > 		"Sorry, not implemented" error at runtime."
> > > 		
> > > 		I get no such error from the above example in grade
> > > 		asm_fast.gc.tr.  Does this mean the reference manual is
> > > 		out of date, or have I just been lucky?
> > 
> > I think that only applies to minimal model (and/or model_non) tabling.
> 
> That is correct.
> 
> > I think the reference manual may be incorrect and/or out of date.
> 
> It is ambiguous. The ambiguity is supposed to be resolved by the previous
> several paragraphs all being about minimal model tabling. Since that seems
> not to be sufficient, I will reword that paragraph.

Thanks.  However, the part of that sentence from the reference manual
which I left out ("... or if you select a garbage collection method
other than the default (conservative) ...") seems to apply to
`:- pragma memo' tabling as well.  In particular, if I compile the
example I gave in grade asm_fast.tr I get a runtime error:

	Mercury runtime: Cannot copy a c_pointer type

Is there any chance of getting `:- pragma memo' working in non-gc
grades?  (We only need it for benchmarking purposes, but it would be
useful, nonetheless, if it's possible.)



David
-- 
David Overton                  Uni of Melbourne     +61 3 8344 1354
dmo at cs.mu.oz.au                Monash Uni (Clayton) +61 3 9905 5779
http://www.cs.mu.oz.au/~dmo    Mobile Phone         +61 4 0337 4393
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