void
mpz_lucnum2_ui (mpz_ptr ln, mpz_ptr lnsub1, unsigned long n)
{
mp_ptr lp, l1p, f1p;
mp_size_t size;
mp_limb_t c;
TMP_DECL;
ASSERT (ln != lnsub1);
/* handle small n quickly, and hide the special case for L[-1]=-1 */
if (n <= FIB_TABLE_LUCNUM_LIMIT)
{
mp_limb_t f = FIB_TABLE (n);
mp_limb_t f1 = FIB_TABLE ((int) n - 1);
/* L[n] = F[n] + 2F[n-1] */
PTR(ln)[0] = f + 2*f1;
SIZ(ln) = 1;
/* L[n-1] = 2F[n] - F[n-1], but allow for L[-1]=-1 */
PTR(lnsub1)[0] = (n == 0 ? 1 : 2*f - f1);
SIZ(lnsub1) = (n == 0 ? -1 : 1);
return;
}
TMP_MARK;
size = MPN_FIB2_SIZE (n);
f1p = TMP_ALLOC_LIMBS (size);
MPZ_REALLOC (ln, size+1);
MPZ_REALLOC (lnsub1, size+1);
lp = PTR(ln);
l1p = PTR(lnsub1);
size = mpn_fib2_ui (l1p, f1p, n);
/* L[n] = F[n] + 2F[n-1] */
#if HAVE_NATIVE_mpn_addlsh1_n
c = mpn_addlsh1_n (lp, l1p, f1p, size);
#else
c = mpn_lshift1 (lp, f1p, size);
c += mpn_add_n (lp, lp, l1p, size);
#endif
lp[size] = c;
SIZ(ln) = size + (c != 0);
/* L[n-1] = 2F[n] - F[n-1] */
c = mpn_double (l1p, size);
c -= mpn_sub_n (l1p, l1p, f1p, size);
ASSERT ((mp_limb_signed_t) c >= 0);
l1p[size] = c;
SIZ(lnsub1) = size + (c != 0);
TMP_FREE;
}
void
check_fib_table (void)
{
int i;
for (i = 1; i <= FIB_TABLE_LIMIT; i++)
ASSERT_ALWAYS (FIB_TABLE(i) != 0);
}
void
mpz_fib2_ui (mpz_ptr fn, mpz_ptr fnsub1, unsigned long n)
{
mp_ptr fp, f1p;
mp_size_t size;
if (n <= FIB_TABLE_LIMIT)
{
MPZ_NEWALLOC (fn, 1)[0] = FIB_TABLE (n);
SIZ(fn) = (n != 0); /* F[0]==0, others are !=0 */
MPZ_NEWALLOC (fnsub1, 1)[0] = FIB_TABLE ((int) n - 1);
SIZ(fnsub1) = (n != 1); /* F[1-1]==0, others are !=0 */
return;
}
size = MPN_FIB2_SIZE (n);
fp = MPZ_NEWALLOC (fn, size);
f1p = MPZ_NEWALLOC (fnsub1, size);
size = mpn_fib2_ui (fp, f1p, n);
SIZ(fn) = size;
SIZ(fnsub1) = size - (f1p[size-1] == 0);
}
