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/* See LICENSE file for copyright and license details. */
#include "internals"
void
zsqr(z_t a, z_t b)
{
/*
* Karatsuba algorithm, optimised for equal factors.
*/
size_t m2;
z_t z0, z1, z2, high, low;
int sign;
if (zzero(b)) {
SET_SIGNUM(a, 0);
return;
}
m2 = zbits(b);
if (m2 <= 16) {
zsetu(a, b->chars[0] * b->chars[0]);
SET_SIGNUM(a, 1);
return;
}
sign = zsignum(b);
SET_SIGNUM(b, 1);
m2 >>= 1;
zinit(z0);
zinit(z1);
zinit(z2);
zinit(high);
zinit(low);
zsplit(high, low, b, m2);
#if 0
zsqr(z0, low);
zsqr(z2, high);
zmul(z1, low, high);
zlsh(z2, z2, m2);
m2 = (m2 << 1) | 1;
zlsh(z1, z1, m2);
zadd(a, z2, z1);
zadd(a, a, z0);
#else
zsqr(z0, low);
zsqr(z2, high);
zmul(z1, low, low);
zlsh(z0, z0, m2 + 1);
zlsh(z1, z1, m2 + 1);
zlsh(a, z2, m2);
m2 <<= 1;
zlsh(z2, z2, m2);
zadd(z2, z2, a);
zsub(a, z2, z1);
zadd(a, a, z0);
#endif
zfree(z0);
zfree(z1);
zfree(z2);
zfree(high);
zfree(low);
SET_SIGNUM(b, sign);
SET_SIGNUM(a, 1);
}
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