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Introduce fq_default_ctx_init_randtest() #2050

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merged 4 commits into from
Sep 5, 2024
Merged

Introduce fq_default_ctx_init_randtest() #2050

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3f54490
introduce fq_default_ctx_init_randtest
GiacomoPope Aug 19, 2024
ed59d18
swap order of function calls
GiacomoPope Aug 23, 2024
1195800
random selection from one of the five internal representations
GiacomoPope Sep 2, 2024
009a93f
shrink p^d for zech testing
GiacomoPope Sep 2, 2024
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9 changes: 6 additions & 3 deletions doc/source/fq_default.rst
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Expand Up @@ -104,10 +104,13 @@ Context Management

Prints the context information to ``stdout``.

.. function:: void fq_default_ctx_randtest(fq_default_ctx_t ctx)
.. function:: void fq_default_ctx_init_randtest(fq_default_ctx_t ctx, flint_rand_t state, int type)

Initializes ``ctx`` to a random finite field. Assumes that
``fq_default_ctx_init`` has not been called on ``ctx`` already.
Initializes ``ctx`` to a random finite field where the prime and degree is
set according to ``type``.
Assumes that ``fq_default_ctx_init`` has not been called on ``ctx`` already.
To see what prime and degrees may be output, see
``type`` in :func:`_nmod_poly_conway_rand`.
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Just to be clear: You are not referring to the internal "type" for fq_default (i.e. fmpz, nmod etc.)?

I have to think about the randomness thing (i.e. which type). Now, this module is not very much tested inside FLINT, unfortunately (however it is tested in Nemo/Oscar), but in general we would like to (1) minimize the time for testing and (2) reduce the complexity of usage. A separate parameter for type obviously increases the complexity, and, furthermore, is inherited from nmod_poly.

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The type here is the one passed into the generation of prime,degree from the nmod conway function and is not related at all the the fq_default type

The design here, hopefully, simply does what practically would happen if you asked for a random context from fq, fq_nmod and fq_zech


.. function:: void fq_default_get_coeff_fmpz(fmpz_t c, fq_default_t op, slong n, const fq_default_ctx_t ctx)

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1 change: 1 addition & 0 deletions src/fq_default.h
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Expand Up @@ -229,6 +229,7 @@ int fq_default_ctx_fprint(FILE * file, const fq_default_ctx_t ctx);
#endif

void fq_default_ctx_print(const fq_default_ctx_t ctx);
void fq_default_ctx_init_randtest(fq_default_ctx_t ctx, flint_rand_t state, int type);

/* Memory management *********************************************************/

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19 changes: 19 additions & 0 deletions src/fq_default/ctx.c
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Expand Up @@ -199,3 +199,22 @@ void fq_default_ctx_modulus(fmpz_mod_poly_t p, const fq_default_ctx_t ctx)
fmpz_mod_poly_set(p, FQ_DEFAULT_CTX_FQ(ctx)->modulus, mod);
}
}

/* FIXME: fq_ctx_init_randtest only tests nmod sized primes, so that's
all we'll do here too? */
void fq_default_ctx_init_randtest(fq_default_ctx_t ctx, flint_rand_t state, int type)
{
ulong prime;
slong degree;
fmpz_t p;

/* select a prime and degree to create the finite field */
prime = _nmod_poly_conway_rand(&degree, state, type);

/* fq_default initialisation wants an fmpz_t for the prime */
fmpz_init(p);
fmpz_set_ui(p, prime);

/* Initialise the context using the prime and degree selected above */
fq_default_ctx_init(ctx, p, degree, "x");
}
16 changes: 16 additions & 0 deletions src/fq_default/test/t-init.c
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Expand Up @@ -81,5 +81,21 @@ TEST_FUNCTION_START(fq_default_init, state)
fmpz_clear(p);
}

for (i = 0; i < 100 * flint_test_multiplier(); i++)
{
fq_default_ctx_t ctx;
fq_default_t fq;

/* Sets the type used internally for prime selection.
See _nmod_poly_conway_rand for more info. */
int type = n_randint(state, 4);

fq_default_ctx_init_randtest(ctx, state, type);
fq_default_init(fq, ctx);
fq_default_clear(fq, ctx);
fq_default_randtest(fq, state, ctx);
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Order has to change here, no?

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yes, sorry about that. Will fix now.

fq_default_ctx_clear(ctx);
}

TEST_FUNCTION_END(state);
}
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