// Naively implemented Blitz++ version.  NCCS = 9

float echo_Blitz(int N, int niters)
{
    Array<float,2> P1(N,N), P2(N,N), P3(N,N), c(N,N);
    Range I(1,N-2), J(1,N-2);

    setInitialConditions(c, P1, P2, P3, N);

    for (int iter=0; iter < niters; ++iter)
    {
        P3(I,J) = (2-4*c(I,J)) * P2(I,J)
          + c(I,J)*(P2(I-1,J) + P2(I+1,J) + P2(I,J-1) + P2(I,J+1))
          - P1(I,J);

        P1 = P2;
        P2 = P3;
    }

    return P1(N/2,N/2);
}