The Isight count is a method for making cube decisions in races. Like the Keith count, it adjusts both players' pip counts to adjust for wastage (such as extra checkers on low points or gaps on high points), then compares the adjusted pip counts to recommend a cube action (double or no double, and take or pass).
The Isight count was developed by Axel Reichert (original article) by using a software tool (called Isight) to design a race formula that balances the competing goals of accuracy (making correct race cube decisions) and effort (not requiring too many adjustments to the pip count). As described in the article, the Isight count has lower average error than the Keith count when tested against a database of ~50,000 endgame positions, with average cube errors 0.0069 vs. 0.0082 respectively (note that both methods answer a large majority of positions correctly, so the average errors are small).
The article also states that the Isight count requires less effort than the Keith count, in the sense that on average it adds fewer penalty pips. However, unlike the Keith count, the Isight count requires you to look at both players' positions to decide how many penalty pips need to be added; for example, the Isight method adds a penalty pip for each empty 4-6 pt gap unless the opponent's corresponding point is also empty, which requires comparing both sides' positions to decide the number of penalty pips to be added. In my opinion this results in the Isight adjustments requiring on average more effort than the Keith count. Still, the Isight count is a popular alternative to the Keith count that you should consider learning for its improved accuracy, especially for positions where players have different numbers of crossovers or checkers remaining (which the Keith count does not account for).
The Isight approach described on this page is equivalent to the approach in the original article, but recommends structuring the calculations in a way that (in my opinion) is simpler and results in fewer mental calculation errors. The original article recommends computing the adjusted pip counts for both players, then increasing the count of the on-roll player by 1/6 and comparing to the other player's count to arrive at a cube decision (double if doubler exceeds taker by at most 6, take if doubler exceeds taker by at least 2). This drill uses an alternative formulation where the on-roll player's adjusted pip count is computed, the point of last take is calculated (defined as PLT = Isight + floor(Isight/6) − 2), then the opponent's adjusted pip count is compared to the point of last take to arrive at a cube decision (double within 4 of point of last take, take if no more than point of last take). These two formulations give the same cube decisions.
Like the Keith count, the Isight count is a reasonable choice for a "default" race formula or a first pass at the cube action for almost any racing position. It does a decent job at recommending the correct cube action in most bearoff positions, including ones that are not pippish.
If both sides have pippish (low wastage) positions, the pippish race formulas are simpler and equally (or more) accurate.
If one or both sides have rollish (very high wastage) positions with many checkers piled up on low points, even the Isight count starts to fail, and more complex methods like EPC are needed to calculate the cube action over the board.
Use whichever method you prefer (half-crossover, cluster counting, or just playing online with the pip count turned on).
Add these penalties to the pip count to get the Isight count:
| Condition | Penalty |
|---|---|
| Each checker beyond 2 on the 1-point | +2 each |
| Each checker beyond 2 on the 2-point | +1 each |
| Each checker beyond 3 on the 3-point | +1 each |
| Each extra checker on the board vs. opponent | +1 each |
| Each empty 4/5/6 point (only if opponent has a checker on that point) | +1 each |
| Each extra crossover vs. opponent | +1 each |
Drill positions are all home-board races, so the crossover penalty never fires in this drill. It's included here so you can apply the Isight count to any race position over the board.
The point of last take (PLT) is the largest Isight count at which the trailer should still take a double:
Let X be the leader's Isight count ("floor" means round down):
| PLT formula | Interpretation |
|---|---|
| PLT = X + floor(X/6) − 2 | Divide by 6, round down, subtract 2, add to Isight count |
After calculating, remember this point of last take (either make a mental note or consider using your fingers), since you will need to retrieve it after determining the trailer's Isight count.
Use the same penalties as Step 2.
The cube action depends on the trailer's Isight count relative to the point of last take that was calculated in Step 3:
Let T be the trailer's Isight count:
| Condition | Cube action | Interpretation |
|---|---|---|
| T > PLT | Pass | Pass beyond the point of last take |
| T ≥ PLT − 4 | Double (initial) | Initial double within 4 of PLT |
| T ≥ PLT − 3 | Redouble | Redouble within 3 of PLT |
| # | Mode | Answer | |
|---|---|---|---|
| No answers yet | |||