[flint-devel] Thread safe FLINT

[Bill H. <goo...@go...>]

I have just committed changes to the development version of FLINT to
make the test_support and memory_manager code thread safe.

I've verified that all tests in fmpz_poly-test can now run in parallel
without issues and fixed numerous issues with thread safety in that
module. All of the functions in fmpz_poly are fully threadsafe, with
the exception of:

* _fmpz_poly_mul_modular is not threadsafe (it stores static
information - Gonzalo and I are working on fixing it).

Some of the biggest issues were:

* mpn_random2 is not threadsafe and segfaults
* the stack based memory manager in FLINT was not threadsafe as it did
not set up per thread stacks
* use of randstate_t's in test support without initialising per thread
was not threadsafe
* everything needs cleaning up when joining threads (i.e. the per
thread memory managers and random states), otherwise you get a memory
leak - there is now a macro in flint.h for doing this cleanup, though
OpenMP does not seem to have a mechanism for doing automatic cleanup
on joining threads, so this is the user's responsibility

I have not checked the thread safety of any other part of FLINT,
however I am unaware of anything else that is not threadsafe except
the random functions in long_extras and the stack based mpz_t
allocator in the mpz_extras module (which no one uses anyway).

It is my hope that FLINT 1.2 will be fully threadsafe.

Note gcc 4.2.4 or higher is currently needed to compile the
development version of FLINT. I'll put some checking in for lower
versions in FLINT 1.2 before releasing (and OpenMP stuff just won't be
available to people with older versions of gcc).

I haven't decided whether to have the tests to run in parallel or not.
Currently some of them run much faster in parallel, and some much
slower.

Bill.