Friday, September 23, 2011

A bit of a problem

Once again, here is a plot of the actual garbage collection counts as a function of heap size:
and we mention that we want to be “beyond the knee” in the curve. So where is that “knee”?

The green line is the plot of f(x) = 6100000/x, or, to put it another way, the plot of x × y = 6100000. The knee in the curve ought to be where x = y = √6100000 ≈ 2470. But look at the chart! Just by eyeballing it, we can see that 2470 is nowhere near what anyone would call the knee.

2 comments:

Unknown said...

It's a smooth curve; the illusion of a "knee" is only because of the scale you've plotted it on. If you plot it such that the x and y axes are equally scaled, the visual "knee" will appear to be where you expect it.

Jrm said...

Exactly right. If you change the scale of x and y you will find that you can put the "knee" anywhere on the curve you want.