static
void mul_aux(vec_GF2& x, const vec_GF2& a, const mat_GF2& B)
{
long n = B.NumRows();
long l = B.NumCols();
if (n != a.length())
Error("matrix mul: dimension mismatch");
x.SetLength(l);
clear(x);
const _ntl_ulong *ap = a.rep.elts();
_ntl_ulong a_mask = 1;
_ntl_ulong *xp = x.rep.elts();
long lw = (l + NTL_BITS_PER_LONG - 1)/NTL_BITS_PER_LONG;
long i;
for (i = 0; i < n; i++) {
if (*ap & a_mask) {
const _ntl_ulong *bp = B[i].rep.elts();
long j;
for (j = 0; j < lw; j++)
xp[j] ^= bp[j];
}
a_mask <<= 1;
if (!a_mask) {
a_mask = 1;
ap++;
}
}
}
void cvt(vec_GF2& x, const vec_zz_p& a)
{
long n = a.length();
x.SetLength(n);
long i;
for (i = 0; i < n; i++)
x.put(i, rep(a[i]));
}
static
void mul_aux(vec_GF2& x, const mat_GF2& A, const vec_GF2& b)
{
long n = A.NumRows();
long l = A.NumCols();
if (l != b.length())
Error("matrix mul: dimension mismatch");
x.SetLength(n);
long i;
for (i = 0; i < n; i++) {
x.put(i, A[i] * b);
}
}
void solve(GF2& d, vec_GF2& X, const mat_GF2& A, const vec_GF2& b)
{
long n = A.NumRows();
if (A.NumCols() != n)
Error("solve: nonsquare matrix");
if (b.length() != n)
Error("solve: dimension mismatch");
if (n == 0) {
X.SetLength(0);
set(d);
return;
}
long i, j, k, pos;
mat_GF2 M;
M.SetDims(n, n+1);
for (i = 0; i < n; i++) {
AddToCol(M, i, A[i]);
}
AddToCol(M, n, b);
long wn = ((n+1) + NTL_BITS_PER_LONG - 1)/NTL_BITS_PER_LONG;
for (k = 0; k < n; k++) {
long wk = k/NTL_BITS_PER_LONG;
long bk = k - wk*NTL_BITS_PER_LONG;
_ntl_ulong k_mask = 1UL << bk;
pos = -1;
for (i = k; i < n; i++) {
if (M[i].rep.elts()[wk] & k_mask) {
pos = i;
break;
}
}
if (pos != -1) {
if (k != pos) {
swap(M[pos], M[k]);
}
_ntl_ulong *y = M[k].rep.elts();
for (i = k+1; i < n; i++) {
// M[i] = M[i] + M[k]*M[i,k]
if (M[i].rep.elts()[wk] & k_mask) {
_ntl_ulong *x = M[i].rep.elts();
for (j = wk; j < wn; j++)
x[j] ^= y[j];
}
}
}
else {
clear(d);
return;
}
}
vec_GF2 XX;
XX.SetLength(n+1);
XX.put(n, 1);
for (i = n-1; i >= 0; i--) {
XX.put(i, XX*M[i]);
}
XX.SetLength(n);
X = XX;
set(d);
return;
}
