The old code used a fold with a function type for the accumulator, as a
kind of trick to process the schema in reverse order from what would
happen otherwise. However, the compiler wasn't doing a good job
optimizing that code. In particular, every intermediate function would
up duplicated twice, for exponential code blow-up. So, instead, I
reversed the input string and then processed the result in the natural
order. Now you can see that the fold accumulator is only referenced
once, while it was referenced twice before.
On 03/05/2017 11:04 AM, Marko Schütz Schmuck wrote:
I looked at the diff, but I do not yet understand why the change
improves the situation.
Could you provide some high-level goal that the change is pursuing? I
expect that would help me in the future...
Best regards,
Marko
On Sun, 05 Mar 2017 10:51:10 -0400,
Adam Chlipala wrote:
With the extensive compile-time evaluation that comes from Ur/Web's style of
metaprogramming, it's not surprising that one would encounter superlinear
scaling in time
or space, applying components like those in UPO. I think your conclusion is
correct that
the type checker isn't to blame. Rather, compile-time reduction was generating
exponential
explosion in code size.
I believe I've fixed the issue, and thanks for reporting it. Don't be surprised
to find
more in the future! (I had only tested CSV import with about 5 fields,
previously.)
On 03/02/2017 04:46 PM, Marko Schütz Schmuck wrote:
Dear All,
I naïvely tried compiling a source code file with a table having 15
attributes, 3 of which form the key. Also, that table is used with
Csv.importTable from upo.
After a few seconds the compiler uses 4GB of memory and 100% CPU and
seems stuck. If I reduce the number of attributes to 12 it compiles in
~2m30s total and with only 4 attributes it's done in ~24s total.
In this case I actually do not need all the attributes, but for a
future extension I would. I wondered whether the type checker is to
blame, but it appears not: with -tc the compiler takes ~24s total for
the file with the 15 attributes.
Any recommendations?
Best regards,
Marko
_______________________________________________
Ur mailing list
[email protected]
http://www.impredicative.com/cgi-bin/mailman/listinfo/ur
