On Sunday, August 10, 2014 6:31:03 AM UTC-7, Dima Pasechnik wrote:
>
> if this is the case then how one would to to reclaim the memory?
> And why this is not a memory leak?
It's not necessarily a leak from the perspective of ecl: the memory
obtained from the operating system may well sit there, ready to be filled
with new lisp objects. From the python perspective you could call this a
memory leak, though. But it's a virtually unavoidable one if you place
multiple memory management systems in the same process that are not
designed to cooperate: each thinks they have a complete view of the world
but they don't. It may well be that ecl/boehm does unmap memory pages every
now and again. But really, in our case the same scenarios can arise with
pari/gp, libsingular, libgap
Would at least restarting ecl release the memory?
>
Possibly.
> (it's not clear how the latter can be done; would maxima_calculus.reset()
> do the job?)
>
restarting ecl is currently not a supported operation, because it would be
a terribly difficult operation to do correctly: all EclObjects in python
memory would somehow have to be "invalidated", a state that currently
doesn't even exist for them. That also means *finding* those objects (or
knowing that there are none-which will never happen because we have plenty
of global EclObjects), which would require an extra expensive facility.
Regardless, of this, symbolics leak anyway:
sage: for i in range(10000000): _=SR.var("t%d"%i)
will steadily eat memory. Probably the pynac symbol table doesn't get
garbage collected. Even if that wouldn't leak then
sage: for i in range(10000000): _=maxima_calculus(SR.var("t%d"%i))
and
sage: from sage.interfaces.maxima_lib import sr_to_max
sage: for i in range(10000000): _=sr_to_max(SR.var("t%d"%i))
would leak for sure via slightly different mechanisms, but for the same
reason: we need to keep symbols alive in python and in maxima, depending on
the lifetime of objects in the other. To garbage collect these, you'd need
cycle detection *across the python/ecl boundary*. So currently, symbols
that have been transported across to maxima have eternal life. It seems
that symbols in SR proper already have eternal life, so it doesn't really
matter. Solving this leak would be really quite hard, so we should probably
call it a "feature".
The solution is to restart sage early and often. It has good facilities for
it, see @parallel.
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