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speed up rising_difference_polynomial slightly

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This commit is contained in:
Fredrik Johansson 2014-05-29 18:09:35 +02:00
parent ef8de95902
commit fd4313b83d
1 changed files with 25 additions and 21 deletions
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46
gamma/rising_fmprb_ui_delta.c
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@ -29,37 +29,41 @@
void
rising_difference_polynomial(fmpz * s, fmpz * c, ulong m)
{
long i, j, k;
fmpz_t t;
long i, j, v;
fmpz_t t;
fmpz_init(t);
arith_stirling_number_1u_vec(s, m, m + 1);
for (k = 0; k < m; k++)
/* Compute the first row */
for (i = 0; i < m; i++)
{
for (i = 0; i <= m - k - 1; i++)
fmpz_set_ui(t, m);
fmpz_mul_ui(t, t, (i + 1));
fmpz_mul(c + i, s + (i + 1), t);
for (j = i + 2; j < m + 1; j++)
{
fmpz_zero(c + m * k + i);
for (j = i + 1; j + k <= m; j++)
{
if (j == i + 1)
{
fmpz_bin_uiui(t, 1+i+k, k);
fmpz_mul_ui(t, t, m * (i+1));
}
else
{
fmpz_mul_ui(t, t, m * (k + j));
fmpz_divexact_ui(t, t, j - i);
}
fmpz_addmul(c + m * k + i, s + j + k, t);
}
fmpz_mul_ui(t, t, m * j);
fmpz_divexact_ui(t, t, j - i);
fmpz_addmul(c + i, s + j, t);
}
}
/* Extend using recurrence and symmetry */
for (v = 1; v < m; v++)
{
for (i = v; i < m - v; i++)
{
fmpz_mul_ui(t, c + (v - 1) * m + (i + 1), i + 1);
fmpz_divexact_ui(c + v * m + i, t, v);
}
for (i = 0; i < v; i++)
fmpz_set(c + v * m + i, c + i * m + v);
}
fmpz_clear(t);
}