Such a good explanation Stremba, thank you!

I can see my opponent holding that 5 point as long as possible, so they may hit another blot, but these extra checkers will definitely allow me to hold off on that as long as possible, and have a better chance of avoiding it (hence the 5% change in being gammoned but no more).

1. Which two percentages are you asking about? The only "win the game" percentages are 45.24 and 54.76 but obviously one's for White and one's for Black, so I think you are talking about different percentages? The 48.70, 48.62, etc. numbers are match winning chances. The "Cubeless mwc" number stands for "Cubeless match winning chance" which is something like a players chance to win the match if the cube isn't in play for the current game.

2. They are shown in order of match winning chance. 48.70 > 48.62 > 48.45 etc. But sometimes they won't be because if a play is evaluated at a higher level than other plays, the plays with the higher evaluation level will be placed ahead of the plays with the lower evaluation level.

3. The plays in greens are considered errors. Bigger errors, "blunders", will be in red. It's easier to see the size of the conceptual errors you are making if you switch the display from match winning chances to normalized equity, by right clicking on a play and going to "Display as".

Thanks Z - all understood!

Can anyone explain why 24/16 is the best move here? It just seems like I'm setting myself up to be attacked on black's next move.

This move makes no sense to me

Apparently half a percent better to win the game than my chosen move, but gives 3 pieces in my home board that can be hit?

The next thing is I'm stuck in his homeboard on the 2 point, not getting a 5 or 6 and then have to reduce my 6 prime to a 5 or 4 prime, giving him a chance of getting out..

1) His board is so weak that you don't mind running.
2) You're forcing him to hit you so he'll be stuck behind your 6-prime while you hopefully dance (don't reenter) so he'll be the one to crunch his board first.

Thanks Uber! Love this forum

I like the term "dance"!

Another question!

Here's the board, and XG doubles. I understand the 25% rule (apparently I had a 28% chance of winning), but I thought there was a high risk of me being gammoned...and in the end I was.

I'm guessing the gammon percentage is fairly low because of black's weak/non existent prime. It says there's a 10.5% chance of a gammon but to me it looks a lot higher.

Surely that's not a good double to take?

Gammon chances are quite low with the 20-anchor. This is a clear take where you have plenty of timing to hold the straggler for a while but won't get gammoned much. Additionally the 10-8 structure is rather gappy and prone to shots. Shift his outfield points to 78 or 89 and note what I would expect to be a significant difference in your winning chances.

Thanks for the reply.

Fair enough I suppose. Unfortunately all it took was a 6/6 from black and then the gammon seemed inevitable.

Plenty of timing to hold the straggler (if it isn't hit of course)? Do mean using the checkers on my 6 point, 7 point and the checker on his 5 point?

To expand on this, not only are you looking to make your opponent crash his board, but you want to be able to pick up some blots when that happens. Never forget — gammons count double. One checker behind a full prime gives a fairly low likelihood of winning gammon. Three or four checkers trapped increases gammon chances considerably.

Thanks Stremba. Yes it looks like from the figures, the gammon was 9.8% with the suggested move, versus 4.7% with my move.

Ok so basically...in this kind of position, if I have a 6 prime and only 1 checker captured...force him to take one of mine, to try and hit more of his..

Thanks

Me again

I was in this position and played 6/3 3/2. I thought that was a good attack and then I'd have another checker on the 8 or 6 point to move to my blot on the next move, assuming it wasn't hit.

XG says 8/5 6/5 is the right move. I would've thought attacking is the right move here, given a 3 prime is pretty useless? I must be missing something...

I played 24/13 below. XG suggests I should have played 22/11.


24/13 showed a game winning percentage of 20.78.
22/11 showed a game winning percentage of 20.81!

I did a rollout on those 2 moves and now 24/13 is 20.83% and 22/11 is 20.60%

So...sometimes with small margins of error, XG is wrong, until you do a rollout?

24/13 seemed like a no-brainer...better chance of hitting a blot with my checker on the 22 point.

Regarding 8/5 6/5, improving from a 2-pt board to a 3-pt board is a good asset long term, often underrated. Also, keep in mind that your 3-prime is in fact a broken 5-prime, also underrated sometimes.

As for the 22/11, you're behind in the race, so you want to keep the straggler on your 24-pt for maximum contact I would guess. Also in that case, his 4-pt board looks scary, but he doesn't have extra ammunition to attack you. (He has even less to attack you on the 24-pt than on the 22-pt in fact.)

Thanks uber, makes sense. It's strange how XG changed the preferable move after a rollout though!

Ok this one is annoying me. Why take the risk? Black get s 61 or 63 on the next roll and I could lose the game

Same game, it tells me to give the computer another chance of winning

Although it says the move I chose has a higher chance of winning the game..!

In your last position (4-1) to play), XG is telling you that your play has an 0.6% better chance of winning, but 15/11 2/1* has a 1.8% better chance of winning a gammon. The extra gammons you win after hitting make the play an overall better choice.

Notice a few other things about the position:

If you make your play (15/11 6/5) your opponent wins immediately with 66 or 64, takes a lead in the race with 65, and has reasonably good chances after 61 and 62.

After XG's play, if Black rolls 51 or 41 he hits but breaks one of his inner points, leaving a blot. Now a hit by you sends a 2nd checker back and gives you gammon chances.

You need to think a little more about how your opponent's upcoming rolls actually play, rather than thinking that leaving a blot just loses for you when you get hit. That's rarely the case.

Thanks for the reply Bill

I saw the increase in my gammon chances, but as it was only a 1.8% increase, I didn't think it was a big factor

I can also see how the opponent would win now with the rolls you mentioned...something I hadn't considered.

I was just wary of the 11, 12, 13, 16 or a 6 on the opponent's following throw. It's definitely a new side of the game to me - taking risks like this for a slightly better chance at the gammon.

It’s not the increase in gammon chances in and of itself that matters, it’s that increase relative to the amount of increased winning chances you get by playing safe.

In a cash game, assuming you have a play that wins 100% but never wins gammon, you get 1 point by making that play. If another play increases gammon chances, but also creates losing chances you either win 2 points or lose 1. Losing therefore costs you 2 points (-1 instead of +1). Winning gammon gives you 1 extra point. Therefore to break even the risky play must increase your gammon chances by twice as much as it increases your chance of losing.

In your example, the gammon chance increased by 1.8%, losing chances by 0.6%. The increase in gammon chances is more than double the increase in losing chances, so it’s correct to take the risk to win more gammons.

Be careful with this in match play. The basic idea still applies, but the value of gammons is not constant like in a cash game. There are match scores where you need less than double gammon chances to take the risk and some where you need more than double. The relevant concept is called gammon price - for money games the gammon price always is 2. You need 2 gammons for each loss.

Just a simple example, consider a 5 point match where you trail 3-1 and you have doubled. Obviously you should be playing very aggressively for a gammon - you win the match if you gammon your opponent. A risk/reward calculation can tell you how aggressively you should play. If you could safely win the current game, you’d tie the match and therefore have a 50% chance of winning it. If you play risky you are risking that 50% chance (you have zero chance if you lose) to increase your MWC by 50%. You risk 50 to gain 50, so you should be willing to trade losses for gammons even up; the gammon price in this situation is 1.

Other scores will give other gammon prices, but unless gammons are meaningless (such as they would be to the leader in my above example), there will always be some ratio of increased gammons to increased losses that will make playing for gammon the correct play.

Thanks for the detailed explanation stremba

I'll try to factor this into my gameplay. Risk the gammons when I need them and when the increase chance of a gammon is much higher than the decreased chance of winning. Understood.

Now the only problem is even trying to think about these percentages without a program like XG. I suppose in real life board play, the only time I would consider this is in examples I've previously experienced (like the board above) or when it's completely obvious to me. I'll learn more examples the more I play.

Another one..!

I rolled 41.

I played 11/7 8/7. The only way he's getting out is a 64 or 63.

XG says the best move is 9/5 6/5. The opponent could then get out with 62, 63, 64, 65. And if he rolls 62 or 64, he hits me as well.

My move



XG's chosen move


Any ideas on this one?

The five point is very valuable. The two most valuable points on the board are the two five points, yours and your opponent’s. It’s usually correct to make the five point when you have an opportunity to do so.

In this specific instance, the other factor working in favor of the five point, besides its value as a permanent long-term asset is that your opponent has only one checker back. As a general rule, you don’t want to try to prime a single checker, but rather attack it and (hopefully) close it out. This is because it’s much easier for one checker to escape a prime - it only takes one good roll - and because once you start attacking, your opponent won’t be able to make an anchor to thwart your attack.

The five point is MUCH more important for an attack. It’s an inner board point; one less number your opponent can use to reenter when hit. It also serves as a decent blocking point. Like with any “rule” in bg, there are exceptions to the “always make the five point” rule, but this position certainly isn’t one of them.

Hi again Stremba!

I (think I) understand how valuable the 5 point is, but this felt like one of those times where a 4 prime would outweight the value of holding the 5 point.

"As a general rule, you don’t want to try to prime a single checker, but rather attack it and (hopefully) close it out. "

Maybe it's this bit that's the most important here? Although to be honest, neither my move or XG'S recommended move set me up in a way to attack on the next move. Maybe XG's move sets me up for a better attack later on, but my concern was a 62 or 64 and it's probably a loss for me.

I'm losing the race though, so maybe XG is saying I must take more risks now to attack that blot, and if that means I get hit, at least I've got a chance of landing on his 5 point...