/* Put in {rootp, ceil(un/k)} the kth root of {up, un}, rounded toward zero.
If remp <> NULL, put in {remp, un} the remainder.
Return the size (in limbs) of the remainder if remp <> NULL,
or a non-zero value iff the remainder is non-zero when remp = NULL.
Assumes:
(a) up[un-1] is not zero
(b) rootp has at least space for ceil(un/k) limbs
(c) remp has at least space for un limbs (in case remp <> NULL)
(d) the operands do not overlap.
The auxiliary memory usage is 3*un+2 if remp = NULL,
and 2*un+2 if remp <> NULL. FIXME: This is an incorrect comment.
*/
mp_size_t
mpn_rootrem (mp_ptr rootp, mp_ptr remp,
mp_srcptr up, mp_size_t un, mp_limb_t k)
{
mp_size_t m;
ASSERT (un > 0);
ASSERT (up[un - 1] != 0);
ASSERT (k > 1);
m = (un - 1) / k; /* ceil(un/k) - 1 */
if (remp == NULL && m > 2)
/* Pad {up,un} with k zero limbs. This will produce an approximate root
with one more limb, allowing us to compute the exact integral result. */
{
mp_ptr sp, wp;
mp_size_t rn, sn, wn;
TMP_DECL;
TMP_MARK;
wn = un + k;
wp = TMP_ALLOC_LIMBS (wn); /* will contain the padded input */
sn = m + 2; /* ceil(un/k) + 1 */
sp = TMP_ALLOC_LIMBS (sn); /* approximate root of padded input */
MPN_COPY (wp + k, up, un);
MPN_ZERO (wp, k);
rn = mpn_rootrem_internal (sp, NULL, wp, wn, k, 1);
/* The approximate root S = {sp,sn} is either the correct root of
{sp,sn}, or 1 too large. Thus unless the least significant limb of
S is 0 or 1, we can deduce the root of {up,un} is S truncated by one
limb. (In case sp[0]=1, we can deduce the root, but not decide
whether it is exact or not.) */
MPN_COPY (rootp, sp + 1, sn - 1);
TMP_FREE;
return rn;
}
else
{
return mpn_rootrem_internal (rootp, remp, up, un, k, 0);
}
}
/* Put in {rootp, ceil(un/k)} the kth root of {up, un}, rounded toward zero.
If remp <> NULL, put in {remp, un} the remainder.
Return the size (in limbs) of the remainder if remp <> NULL,
or a non-zero value iff the remainder is non-zero when remp = NULL.
Assumes:
(a) up[un-1] is not zero
(b) rootp has at least space for ceil(un/k) limbs
(c) remp has at least space for un limbs (in case remp <> NULL)
(d) the operands do not overlap.
The auxiliary memory usage is 3*un+2 if remp = NULL,
and 2*un+2 if remp <> NULL. FIXME: This is an incorrect comment.
*/
mp_size_t
mpn_rootrem (mp_ptr rootp, mp_ptr remp,
mp_srcptr up, mp_size_t un, mp_limb_t k)
{
ASSERT (un > 0);
ASSERT (up[un - 1] != 0);
ASSERT (k > 1);
if ((remp == NULL) && (un / k > 2))
/* call mpn_rootrem recursively, padding {up,un} with k zero limbs,
which will produce an approximate root with one more limb,
so that in most cases we can conclude. */
{
mp_ptr sp, wp;
mp_size_t rn, sn, wn;
TMP_DECL;
TMP_MARK;
wn = un + k;
wp = TMP_ALLOC_LIMBS (wn); /* will contain the padded input */
sn = (un - 1) / k + 2; /* ceil(un/k) + 1 */
sp = TMP_ALLOC_LIMBS (sn); /* approximate root of padded input */
MPN_COPY (wp + k, up, un);
MPN_ZERO (wp, k);
rn = mpn_rootrem_internal (sp, NULL, wp, wn, k, 1);
/* the approximate root S = {sp,sn} is either the correct root of
{sp,sn}, or one too large. Thus unless the least significant limb
of S is 0 or 1, we can deduce the root of {up,un} is S truncated by
one limb. (In case sp[0]=1, we can deduce the root, but not decide
whether it is exact or not.) */
MPN_COPY (rootp, sp + 1, sn - 1);
TMP_FREE;
return rn;
}
else /* remp <> NULL */
{
return mpn_rootrem_internal (rootp, remp, up, un, k, 0);
}
}
