variables pre-evaluation in loop range spliting

I would like to multithread a for loop but I have some variable inside my loop what need to know the previous state. Well it's not quite easy to explain.

Here is an exemple :

    double mu1 = 0, q1 = 0;
    double max_sigma = 0, max_val = 0;
    for( i = 0; i < N; i++ )
    {
        double p_i, q2, mu2, sigma;
        p_i = h[i]*scale;
        mu1 *= q1;
        q1 += p_i;
        q2 = 1. - q1;

        if(std::min(q1,q2) < FLT_EPSILON || std::max(q1,q2) > 1. -FLT_EPSILON )
            continue;

        mu1 = (mu1 + i*p_i)/q1;
        mu2 = (mu - q1*mu1)/q2;
        sigma = q1*q2*(mu1 - mu2)*(mu1 - mu2);
        if( sigma > max_sigma )
        {
            max_sigma = sigma;
            max_val = i;
        }
    }

scale is a double scalar value.

h is a std::vector<std::uint64_t>

If I split the range in sevral part for process any sub I can locally (in each thread) compute first p_i.

But I don't see how I could determine the value mu1.

So my question is : Is there any way to determine mu1 at the begining of a thread for a range B without prior of the result of mu1 what have been processed in a thread for a range A? If yes, how?