/// <summary>
/// Generates the zeta tables
/// </summary>
static void init_ntt()
{
int i, j, k;
var tmp = new int16_t[128];
tmp[0] = MONT;
for (i = 1; i < 128; ++i)
{
tmp[i] = fqmul(tmp[i - 1], KYBER_ROOT_OF_UNITY * MONT % KYBER_Q);
}
for (i = 0; i < 128; ++i)
{
zetas[i] = tmp[tree[i]];
}
k = 0;
for (i = 64; i >= 1; i >>= 1)
{
for (j = i; j < 2 * i; ++j)
{
zetas_inv[k++] = -tmp[128 - tree[j]];
}
}
zetas_inv[127] = MONT * (MONT * (KYBER_Q - 1) * ((KYBER_Q - 1) / 128) % KYBER_Q) % KYBER_Q;
}
public static int16_t csubq(int16_t a)
{
var result = a - KYBER_Q;
result += (a >> 15) & KYBER_Q;
return((int16_t)result);
}
public static int16_t barrett_reduce(int16_t a)
{
var t = BR * a;
t >>= 26;
t *= KYBER_Q;
return((int16_t)(a - t));
}
public static void basemul(Span <N2, int16_t> r, Span <N2, int16_t> a, Span <N2, int16_t> b, int16_t zeta)
{
r[0] = fqmul(a[1], b[1]);
r[0] = fqmul(r[0], zeta);
r[0] += fqmul(a[0], b[0]);
r[1] = fqmul(a[0], b[1]);
r[1] += fqmul(a[1], b[0]);
}
public static int16_t fqmul(int16_t a, int16_t b) => montgomery_reduce((int32_t)a * b);