Re: [Xsb-development] Prolog Profiling in XSB

[Bart D. <Bar...@cs...>]

> The nextinstruction macro includes a test to see if the interrupt
> bit has been set.  That's the overhead I'd rather avoid.

Would it be enough you think, to put the test only in control flow
instructions (call, execute, try, retry ...) ? That would save some
overhead. You would miss little in accuracy compared to what you do:
failure can make my count go to another predicate than yours, but
that seems all and no big deal.

In addition, how about the following: have a call and a prof_call
instruction (and similar for the other control flow instructions); the
loader can change call (coming from a .O) to prof_call depending on a
runtime(!)  option. The prof_call gets as extra argument(s) over the
call instruction just enough information to make the storing of the
profiling information quick - basically the address of the counter to
increase.

I have done that in hProlog - but it is not based on an interrupt, it
always does the count++ - and especially the possibility to do
profiling on a portion of the program which you decide about on the
fly, is a joy: set the profile flag and (re)consult the modules.
No need to get out of Prolog and start a dedicated profiling system.
The overhead is low (just measured 5% on a test which hProlog runs
almost twice as fast as XSB)
The code size overhead is from 5% for the hProlog equivalent of XSB's
syslib (and of comparable source code size) to 20% for THE benchmark.
That overhead includes the space for the counters (one per call site
and per backtracking instruction).

I don't have to deal with dynamic predicates - I am sure that makes
my life easier. I have not done builtin predicates yet.

Cheers

Bart