Adventures in Cython Templating

Fpylll makes heavy use to Cython to expose Fplll’s functionality to Python. Fplll, in turn, makes use of C++ templates. For example, double, long double, dd_real ( and mpfr_t ( are supported as floating point types. While Cython supports C++ templates, we still have to generate code for all possible instantiations of the C++ templates for Python to use/call. The way I implemented these bindings is showing its limitations. For example, here’s how attribute access to the dimension of the Gram-Schmidt object looks like:

    def d(self):
        Number of rows of ``B`` (dimension of the lattice).

        >>> from fpylll import IntegerMatrix, GSO, set_precision
        >>> A = IntegerMatrix(11, 11)
        >>> M = GSO.Mat(A)
        >>> M.d

        if self._type == gso_mpz_d:
            return self._core.mpz_d.d
            if self._type == gso_mpz_ld:
                return self._core.mpz_ld.d
        if self._type == gso_mpz_dpe:
            return self._core.mpz_dpe.d
        IF HAVE_QD:
            if self._type == gso_mpz_dd:
                return self._core.mpz_dd.d
            if self._type == gso_mpz_qd:
                return self._core.mpz_qd.d
        if self._type == gso_mpz_mpfr:
            return self._core.mpz_mpfr.d

        if self._type == gso_long_d:
            return self._core.long_d.d
            if self._type == gso_long_ld:
                return self._core.long_ld.d
        if self._type == gso_long_dpe:
            return self._core.long_dpe.d
        IF HAVE_QD:
            if self._type == gso_long_dd:
                return self._core.long_dd.d
            if self._type == gso_long_qd:
                return self._core.long_qd.d
        if self._type == gso_long_mpfr:
            return self._core.long_mpfr.d

        raise RuntimeError("MatGSO object '%s' has no core."%self)

In the code above uppercase IF and ELSE are compile-time conditionals, lowercase if and else are run-time checks. If we wanted to add Z_NR<double> to the list of supported integer types (yep, Fplll supports that), then the above Python approximation of a switch/case statement would grow by a factor 50%. The same would have to be repeated for every member function or attribute. There must be a more better way.

Continue reading “Adventures in Cython Templating”

Fplll Days 3: July 6 – 14, Amsterdam

We’ll have an fplll coding sprint aka “FPLLL Days” in July. This time around, we plan a slightly modified format compared to previous instances. That is, in order to encourage new developers to get involved, we plan to have a 2 day tutorial session (shorter or longer depending on participants/interest) before the start of FPLLL Days proper.

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fplll 5.1 and fpylll 0.2.4dev

New versions of fplll and fpylll were released today. I’ve reproduced release notes below for greater visibility. The biggest user-visible changes for fplll are probably that

  • CVP enumeration is not experimental any more,
  • support for external enumeration libraries (go write that GPU implementation of enumeration) was added and
  • support for OSX was greatly improved.

On the fpylll side, the biggest user-visible changes are probably various API updates and a much nicer strategy/framework for gathering statistics about BKZ.

The next version of fplll will contain support for LLL reduction on Gram matrices.

Continue reading “fplll 5.1 and fpylll 0.2.4dev”