Comment by dfabulich | Hacker News Reader

Comment by dfabulich | Hacker News Reader

Parent Full thread

The C code in this article is a mirror of the code from Appendix 2 in Vitter's paper, which I guess explains/excuses the abbreviated variable names. The paper says things like, "use an exponentially distributed random variate Y," and uses variable names like n, N, U, S, X, y1, and y2 in the appendix.

Nonetheless, I find this coding style unreadable. "Y" is not a very good name for an exponentially distributed random variate, especially in a function that defines 24 variables with mostly meaningless names. :-(

var naming aside, the whitespacing is perplexing:

      U = random_double(); negSreal=-S;
      y1=exp(log(U*Nreal/qu1real)*nmin1inv);
      Vprime = y1 * (-X/Nreal+1.0)*(qu1real/(negSreal+qu1real));
      if(Vprime <= 1.0) break;       y2=1.0; top = -1.0+Nreal;       if(-1+n > S){bottom=-nreal+Nreal;limit=-S+N;}
      else{bottom=-1.0+negSreal+Nreal; limit=qu1;}

Sometimes two statements per line, sometimes one. Sometimes spaces before and after equals, sometimes none. Sometimes multiple ifs, breaks and statements on one line.

It looks like it was copy-pasted from a pdf. Maybe it was.

I feel like 2 seconds in an ide would have saved readability quite a bit. A simple automated cleanup would have helped worlds.

On the other hand, you need the original names in order to reference back to the paper.

random_variate_y

:P

Reply on news.ycombinator.com