Previous: What does Pips mean?, Up: Analyzing

When bearing off checkers, you may notice a display showing the
current *epc* value (next to the display of
*Pips*). The epc display can be turned on or off
under menu *Settings —> Options —>
Display* (at least in the current version, as of June 2005).

*epc* stands for Effective Pip Count, and is an
alternative measurement of the *goodness* of the
position. The usual pip count can be a misleading
*goodness* estimate when both players are bearing
off. What is more important (for making cubing decisions) is
*the expected number of rolls* each player needs
to bear off hes checkers.

The effective pip count is defined as this expected number of remaining rolls, multiplied with the average number of pips in a roll, which is 8.167. (The average number of pips in a roll would be 7 if rolling a double wouldn't yield a double pip count – i.e. a double-6 yields 24 pips, not 12.)

Thus, epc takes into account not only the current pip count, but also the expected pip wastage:

- effective pip count (epc) = pip count + expected pip wastage

An example:

- Position: 5 checkers on the 1-point, 4 checkers on the 2-point.
- Pip count: 5x1 + 4x2 = 13
- epc: 2.189 (expected number of remaining rolls) * 8.167 = 17.878
- Wasted: 17.878 - 13 = 4.878

It's clear (hopefully) that the expected pip wastage (and hence
the *epc*) increases with more checkers on lower
points (e.g. you get pip wastage when rolling a 6 to bear off a
checker from the 2- or 1-point).

It is further explained on BackGammon Galore, especially in a post by Douglas Zare.

How do one calculate the epc then, or the expected number of
remaining rolls? Gnu BG uses the one-sided bearoff database, which
contains the change of bearing off the final checker in any given
number of rolls. A player would probably use some quite complicated
heuristics (please see the aforementioned post by Douglas Zare,
*and do get back here and explain it!*)