void _arb_sin_cos_taylor_rs(mp_ptr ysin, mp_ptr ycos,
mp_limb_t * error, mp_srcptr x, mp_size_t xn, ulong N,
int sinonly, int alternating)
{
mp_ptr s, t, xpow;
mp_limb_t new_denom, old_denom, c;
slong power, k, m;
int cosorsin;
TMP_INIT;
TMP_START;
if (2 * N >= FACTORIAL_TAB_SIZE - 1)
{
flint_printf("_arb_sin_cos_taylor_rs: N too large!\n");
abort();
}
if (N <= 1)
{
if (N == 0)
{
flint_mpn_zero(ysin, xn);
if (!sinonly) flint_mpn_zero(ycos, xn);
error[0] = 0;
}
else if (N == 1)
{
flint_mpn_copyi(ysin, x, xn);
if (!sinonly) flint_mpn_store(ycos, xn, LIMB_ONES);
error[0] = 1;
}
}
else
{
/* Choose m ~= sqrt(num_terms) (m must be even, >= 2) */
m = 2;
while (m * m < N)
m += 2;
/* todo: merge allocations */
xpow = TMP_ALLOC_LIMBS((m + 1) * xn);
s = TMP_ALLOC_LIMBS(xn + 2);
t = TMP_ALLOC_LIMBS(2 * xn + 2); /* todo: 1 limb too much? */
/* higher index ---> */
/* | ---xn--- | */
/* xpow = | <temp> | x^m | x^(m-1) | ... | x^2 | x | */
#define XPOW_WRITE(__k) (xpow + (m - (__k)) * xn)
#define XPOW_READ(__k) (xpow + (m - (__k) + 1) * xn)
mpn_sqr(XPOW_WRITE(1), x, xn);
mpn_sqr(XPOW_WRITE(2), XPOW_READ(1), xn);
for (k = 4; k <= m; k += 2)
{
mpn_mul_n(XPOW_WRITE(k - 1), XPOW_READ(k / 2), XPOW_READ(k / 2 - 1), xn);
mpn_sqr(XPOW_WRITE(k), XPOW_READ(k / 2), xn);
}
for (cosorsin = sinonly; cosorsin < 2; cosorsin++)
{
flint_mpn_zero(s, xn + 1);
/* todo: skip one nonscalar multiplication (use x^m)
when starting on x^0 */
power = (N - 1) % m;
for (k = N - 1; k >= 0; k--)
{
c = factorial_tab_numer[2 * k + cosorsin];
new_denom = factorial_tab_denom[2 * k + cosorsin];
old_denom = factorial_tab_denom[2 * k + cosorsin + 2];
/* change denominators */
if (new_denom != old_denom && k < N - 1)
{
if (alternating && (k % 2 == 0))
s[xn] += old_denom;
mpn_divrem_1(s, 0, s, xn + 1, old_denom);
if (alternating && (k % 2 == 0))
s[xn] -= 1;
}
if (power == 0)
{
/* add c * x^0 -- only top limb is affected */
if (alternating & k)
s[xn] -= c;
else
s[xn] += c;
/* Outer polynomial evaluation: multiply by x^m */
if (k != 0)
{
mpn_mul(t, s, xn + 1, XPOW_READ(m), xn);
flint_mpn_copyi(s, t + xn, xn + 1);
}
power = m - 1;
}
else
{
if (alternating & k)
s[xn] -= mpn_submul_1(s, XPOW_READ(power), xn, c);
else
s[xn] += mpn_addmul_1(s, XPOW_READ(power), xn, c);
power--;
}
}
/* finally divide by denominator */
if (cosorsin == 0)
{
mpn_divrem_1(t, 0, s, xn + 1, factorial_tab_denom[0]);
/* perturb down to a number < 1 if necessary. note that this
does not invalidate the error bound: 1 - ulp is either
1 ulp too small or must be closer to the exact value */
if (t[xn] == 0)
flint_mpn_copyi(ycos, t, xn);
else
flint_mpn_store(ycos, xn, LIMB_ONES);
}
else
{
mpn_divrem_1(s, 0, s, xn + 1, factorial_tab_denom[0]);
mpn_mul(t, s, xn + 1, x, xn);
flint_mpn_copyi(ysin, t + xn, xn);
}
}
/* error bound (ulp) */
error[0] = 2;
}
TMP_END;
}
void _arb_exp_taylor_rs(mp_ptr y, mp_limb_t * error,
mp_srcptr x, mp_size_t xn, ulong N)
{
mp_ptr s, t, xpow;
mp_limb_t new_denom, old_denom, c;
slong power, k, m;
TMP_INIT;
TMP_START;
if (N >= FACTORIAL_TAB_SIZE - 1)
{
flint_printf("_arb_exp_taylor_rs: N too large!\n");
abort();
}
if (N <= 3)
{
if (N <= 1)
{
flint_mpn_zero(y, xn);
y[xn] = N;
error[0] = 0;
}
else if (N == 2)
{
flint_mpn_copyi(y, x, xn);
y[xn] = 1;
error[0] = 0;
}
else
{
/* 1 + x + x^2 / 2 */
t = TMP_ALLOC_LIMBS(2 * xn);
mpn_sqr(t, x, xn);
mpn_rshift(t + xn, t + xn, xn, 1);
y[xn] = mpn_add_n(y, x, t + xn, xn) + 1;
error[0] = 2;
}
}
else
{
/* Choose m ~= sqrt(num_terms) (m must be even, >= 2) */
/* TODO: drop evenness assumption since we don't have sign issues here? */
/* TODO: then just need to fix power construction below... */
m = 2;
while (m * m < N)
m += 2;
/* todo: merge allocations */
xpow = TMP_ALLOC_LIMBS((m + 1) * xn);
s = TMP_ALLOC_LIMBS(xn + 2);
t = TMP_ALLOC_LIMBS(2 * xn + 2); /* todo: 1 limb too much? */
/* higher index ---> */
/* | ---xn--- | */
/* xpow = | <temp> | x^m | x^(m-1) | ... | x^2 | x | */
#define XPOW_WRITE(__k) (xpow + (m - (__k)) * xn)
#define XPOW_READ(__k) (xpow + (m - (__k) + 1) * xn)
flint_mpn_copyi(XPOW_READ(1), x, xn);
mpn_sqr(XPOW_WRITE(2), XPOW_READ(1), xn);
for (k = 4; k <= m; k += 2)
{
mpn_mul_n(XPOW_WRITE(k - 1), XPOW_READ(k / 2), XPOW_READ(k / 2 - 1), xn);
mpn_sqr(XPOW_WRITE(k), XPOW_READ(k / 2), xn);
}
flint_mpn_zero(s, xn + 1);
/* todo: skip one nonscalar multiplication (use x^m)
when starting on x^0 */
power = (N - 1) % m;
for (k = N - 1; k >= 0; k--)
{
c = factorial_tab_numer[k];
new_denom = factorial_tab_denom[k];
old_denom = factorial_tab_denom[k+1];
/* change denominators */
if (new_denom != old_denom && k < N - 1)
{
mpn_divrem_1(s, 0, s, xn + 1, old_denom);
}
if (power == 0)
{
/* add c * x^0 -- only top limb is affected */
s[xn] += c;
/* Outer polynomial evaluation: multiply by x^m */
if (k != 0)
{
mpn_mul(t, s, xn + 1, XPOW_READ(m), xn);
flint_mpn_copyi(s, t + xn, xn + 1);
}
power = m - 1;
}
else
{
s[xn] += mpn_addmul_1(s, XPOW_READ(power), xn, c);
power--;
}
}
/* finally divide by denominator */
mpn_divrem_1(y, 0, s, xn + 1, factorial_tab_denom[0]);
/* error bound (ulp) */
error[0] = 2;
}
TMP_END;
}
