Incorrect AoS initialization indices in CPU cache AoS vs SoA article

[marvinthang]

Hi, I think there is a small bug in the AoS initialization code in the AoS vs SoA article.

Current code:

for (int i = 0; i < M; i++)
    q[k][0] = p[i];
    
    for (int j = 1; j < D; j++)
        q[i][0] ^= (q[j][i] = rand()); 
        
    k = q[k][0]; 
}

I believe the intended logic is to initialize row q[k], so the inner loop should write to q[k][j], not q[j][i].

Also, after xoring random fields into q[k][0], q[k][0] no longer directly stores the next pointer. So k = q[k][0] is not correct here. The next pointer should still be p[i].

Suggested fix:

for (int i = 0; i < M; i++) {
    q[k][0] = p[i];

    for (int j = 1; j < D; j++) {
        q[k][0] ^= (q[k][j] = rand());
    }

    k = p[i];
}

Thanks for the great article!