gistfile1.cpp

float acc[N];
acc[0] = S::identity();
for (int i = 0; i < (N-1); ++i) {
	acc[i + 1] = S::op(acc[i], x[i]);
}

float dacc0[N];
dacc0[N - 1] = 1.0f;
for (int i = (N - 1); i > 0; --i) {
	dacc0[i - 1] = S::dop0(acc[i], x[i]);
}

float y[N];
for (int i = 0; i < N; ++i) {
	float dacc1 = S::dop1(acc[i], x[i]);
	y[i] = dacc1*dacc0[i];
}