void _fmpq_poly_scalar_mul_ui(fmpz * rpoly, fmpz_t rden,
const fmpz * poly, const fmpz_t den, slong len,
ulong c)
{
fmpz_t gcd; /* GCD( den, c ) */
if (c == 0)
{
_fmpz_vec_zero(rpoly, len);
fmpz_one(rden);
return;
}
fmpz_init(gcd);
fmpz_set_ui(gcd, c);
fmpz_gcd(gcd, gcd, den);
if (*gcd == WORD(1))
{
_fmpz_vec_scalar_mul_ui(rpoly, poly, len, c);
fmpz_set(rden, den);
}
else
{
ulong gcd2 = fmpz_get_ui(gcd);
ulong c2 = c / gcd2;
_fmpz_vec_scalar_mul_ui(rpoly, poly, len, c2);
fmpz_fdiv_q_ui(rden, den, gcd2);
}
fmpz_clear(gcd);
}
void
fmpz_randtest_mod_signed(fmpz_t f, flint_rand_t state, const fmpz_t m)
{
/* Randomly generate m/2 when included in the range */
if ((n_randlimb(state) % 32 == 1) && (fmpz_fdiv_ui(m, 2) == 0))
{
fmpz_fdiv_q_ui(f, m, UWORD(2));
}
else
{
fmpz_t t;
fmpz_init(t);
fmpz_tdiv_q_ui(t, m, UWORD(2));
fmpz_randtest_mod(t, state, t);
if (n_randlimb(state) & UWORD(1))
{
fmpz_neg(t, t);
}
fmpz_set(f, t);
fmpz_clear(t);
}
}
void
_arb_poly_get_scale(fmpz_t scale, arb_srcptr x, slong xlen,
arb_srcptr y, slong ylen)
{
slong xa, xb, ya, yb, den;
fmpz_zero(scale);
/* ignore zeros (and infs/nans!); find the first and last
finite nonzero entries to determine the scale */
xa = 0;
xb = xlen - 1;
while (xa < xlen && arf_is_special(arb_midref(x + xa))) xa++;
while (xb > xa && arf_is_special(arb_midref(x + xb))) xb--;
ya = 0;
yb = ylen - 1;
while (ya < ylen && arf_is_special(arb_midref(y + ya))) ya++;
while (yb > ya && arf_is_special(arb_midref(y + yb))) yb--;
/* compute average of exponent differences, weighted by the lengths */
if (xa <= xb && ya <= yb && (xa < xb || ya < yb))
{
fmpz_add(scale, scale, ARF_EXPREF(arb_midref(x + xb)));
fmpz_sub(scale, scale, ARF_EXPREF(arb_midref(x + xa)));
fmpz_add(scale, scale, ARF_EXPREF(arb_midref(y + yb)));
fmpz_sub(scale, scale, ARF_EXPREF(arb_midref(y + ya)));
den = (xb - xa) + (yb - ya);
/* scale = floor(scale / den + 1/2) = floor((2 scale + den) / (2 den)) */
fmpz_mul_2exp(scale, scale, 1);
fmpz_add_ui(scale, scale, den);
fmpz_fdiv_q_ui(scale, scale, 2 * den);
}
}
