# Explanation of roofline model

I am currently studying the roofline model. Wikipedia [2] shows the following example graph:

The diagonal line shows $$\beta * I$$. But I do not understand why this line does not go through the zero point. If $$I = 0$$ so should $$\beta * I = 0$$. What am I misunderstanding here?

• Are you positive there is a zero point? The lines would appear to be at $1/8$. Feb 12, 2021 at 17:42

The axes are in logarithmic scale, and so don't really have a zero point. What you are seeing is $$\log P = \min(\log I + \log \beta, \log \pi).$$ The striking part is that the slope of the line is always the same.