| When I play a match which has been recorded online, I run it through Snowie to find where my errors are. Snowie can zip through a match with full 3-ply analysis (not rollouts), huge search space, 100% speed, in 15 to 30 minutes. I then replay the match, and Snowie will tell me what my major errors were.
Most of the time I take Snowie's word when it says I have made an error. The program is damn good, and is usually correct. For some positions, however, I am not convinced that Snowie is right. I subject these positionsto a rollout.
Because I want the answers quickly, the rollout parameters I use arenot good enough so the results can be trusted with complete accuracy. My parameters are:
2-ply for play decisions
72 trials with variance reduction
Super-tiny search space
Cubeless
No truncation until bearoff data base is reached
With these parameters, I can usually get rollout results in a few minutes.
The 2-ply rollout is a big improvement over 1-ply. Snowie plays the checkers considerably better, so the results are more trustworthy.72 trials with variance reduction usually comes out to the equivalent of about 1000 or 1500 games. While I don't claim to understand the variance reduction technique fully, I have been impressed with the results -- they seem intuitively to be quite accurate. I have also been assured byseveral knowledgable people that the technique is sound. So, I have learned to trust variance reduction. My sample size isn't too great,but the 95% confidence level is usually smaller than .05 so the results don'tfigure to be too far off.
About my other parameters: Super-tiny search space is generally sufficient. Snowie will usually find the best play among its topthree 1-ply choices, and even if it doesn't most of the time that won'thave a serious effect on the rollouts. I run them cubeless becausecubeful rollouts take more time and lend another element of uncertainty to the results if Snowie is misevaluating the general position. I run therollouts to completion for the same reason -- a major Snowie misevaluationcan lead to distorted results with truncation. The bearoff database issafe, so there is no harm truncating when that is reached.
Obviously more accuracy can be achieved with different parameters, suchas 3-ply rollouts, more trials, and larger search space. There is a tradeoffin time for each of these improvements, and I find the parameters I usegenerally give decent results quickly.
Most of the time when I roll out my errors, the rollout echoes Snowie'3-ply opinion and I have egg on my face, with the only new point ofinterest being just how large an error I made. On occasion, however,I am vindicated, as Snowie reverses its opinion on the rollout. It shouldbe noted that there tends to be a bias in the rollouts in favor of Snowie's 3-ply opinion. The reason is that Snowie is basing its 3-plyevaluation partly on how it thinks the position should be handled, so inthe rollout it will back up this decision and play the position that wayright or wrong. Thus, when Snowie does reverse itself in the rollout,the position is noteworthy.
I have gathered a collection of such positions from matches I played during thelast few weeks. There is nothing particularly unusual about most of these positions that I can see. They are your normal everyday sort of position which, for some reason, Snowie appears to have misevaluated. These arenot small technical errors. They are big conceptual errors, where the difference between Snowie's 3-ply evaluation and the rollout resultsis quite large.
Why does Snowie make mistakes? For the same reasons that we humans do.Snowie analyzes a position by assessing and weighing various parameters, just like we do. It is usually better equipped to take all theseparameters into account and weigh them properly than we mere mortals,which is why its judgment is usually better than ours. However, a position can pop up where, for some reason, Snowie's weights are not an accuraterepresentation of what is important. When this happens, Snowie can make a big error in exactly the same way that we do.
What is interesting is that in many of these positions, my choice of playwas based on principles which I have learned from seeing Snowie's opinionof similar positions. Thus, finding Snowie getting them wrong is oftenquite surprising.
The positions are not in any particular order -- just as I found them.
164
130 | 
          
 
         
| White 0
7 point match
Blue 0 |
A simple concept. Is it worth breaking the five-prime in order to makethe ace point? Making the ace point will certainly win more gammons.If White stays on the bar, I will have time to pick up White's otherblot and bring my men around with only the two-point game to be feared.However, if White enters quickly, things may not go well. My bar pointwill be lost, and I probably won't be able to recover it. White willbe able to escape with fives and sixes, and he has enough outfield controlso he can keep his position in one piece. I have a lot of checkers tobring around, and one of them might not make it home. It is easy to seehow White can win this online game frontwards.
Holding the five-prime with 24/20, 15/13 looked to me to be better. It wouldnot be a disaster if White hit the blot on my ace point, since White wouldstill have a lot of work to do to extricate everybody. In addition, Iwould immediately be attacking White's blot on my eight point. But wasmy thinking too much 1970's prime oriented? Is the brute force approachbetter here? Snowie thought it was.
3-ply evaluation 7/1 .86020/16, 15/13 .801 The rollout told another story.
Rollout results 24/20, 15/13 .7527/1 .722 Why did Snowie get this wrong? Sometimes Snowie seems to underestimatethe value of primes and timing problems. Apparently Snowie didn't seehow likely White's position is to crunch if I just hold the five-primeand sit on the position.
164
124 |
| White 0
7 point match
Blue 0 |
This is the same game, one roll later. The theme is exactly the same. Onceagain I have the choice between making my ace point or holding the bar point.
3-ply evaluation 20/18, 7/1 .99020/12 .881 This time Snowie not only said that making the ace point was correct,it assessed my pure play as a big blunder. Once again I was vindicatedby the rollout.
Rollout results 20/12 .92820/18, 7/1 .888 I have often been dinged for making the same conceptual error onseveral consecutive plays. It is nice to see Snowie falling into thatsame trap for a change.
92
109 |
  
  
| White 2
7 point match
Blue 2 |
This one looked simple enough. I can't keep my full prime, so I might aswell cover the two point with 9/2 and try to win from there. I may beable to scramble my back checker up and out if White stays on the bar,and if White enters I still have my five-prime so I have a reasonable chanceto win the priming battle. Could the super-pure 8/3, 5/3 be right? Nah.Getting hit would be a major disaster, since White would be ready to escapewith a six while I am stuck on the bar. If White doesn't hit I still haveto cover the blot on the two point, and even then I will have work to do.Making the three point is a play I might have made several years ago, butthe bots have taught me that super-purity isn't necessarily right in thissort of position.
3-ply evaluation 8/3, 5/3 .4739/2 .264 What is this? Snowie not only likes making the three point better, but itdinged my play as a double whopper. The bot and the human have swappedplaces, with the bot making the super-pure play and the human themore tactical play. Could Snowie possibly be right on this one? I foundit hard to believe.
Rollout results 9/2 .1978/3, 5/3 .139 Much better! Why did Snowie get this so wrong, when all our experiencewith the bots tells us that we would expect it to lean towards 9/2. Ireally don't understand what happened. Yes there are some duplicationfactors after making the three point since I would need aces and maybe sixeson both sides of the board if White misses the shot, but Snowie is usuallyvery good at picking up on relevant duplication. It looks like Snowieis simply overevaluating the importance of purity in this particularprime vs. prime battle. While playing pure is often correct, this simplyisn't the time for it.
166
163 |
   
 
     
| White 0
7 point match
Blue 3 |
White on roll: Cube action?
I used to take too many cubes like this. Now I respect the power of apotential blitz when I am On the Bar and am staring an attack in the face.In my favor is an even race, White having three men back, and White nothaving too much attack material up front. Still, White has enough powerto do plenty of damage, and I figure to come out with an inferior positioneven if things go well. Also the match score made me more hesitant totake, since my recube vig would be less than normal due to my lead in thematch.
3-ply evaluation Cubeless equity: .453Double, take: .824No double: .673Double, pass: 1.000 Ding, says Snowie. Easy take. Pass is a huge blunder.
Was this really the case? Should I go back to taking cubes such as this?
Rollout results Cubeless equity: .554Double, pass: 1.000No double: .771Double, take: 1.049 Not so, says the rollout. White's position really is that strong. I wouldhave a money take, but at the match score I appear to have a close pass.It is not clear to me why Snowie misevaluated this position so badly.The bots have consistently been punishing me for taking this type ofposition when I am on the bar and in danger of being attacked without muchon my side of the board. I guess Snowie was overly influenced by the raceand White's three men back, and somehow didn't see just how strong White'spotential is. The key is that White doesn't have to play a blitzing game.He can play positionally if the dice so dictate, and he will still havea clear advantage. This apparently is what Snowie failed to see in itsevaluation but what became clear in the rollout.
152
109 |
| White 1
19 point match
Blue 4 |
Gotta fight for that five point, right? Don't worry about blots.8/5*, 7/1 must be better than the stagnant 7/1, 4/1. If I letWhite anchor, my advantage goes down the drain. The gains from hittingare huge when it works, and if I am hit back it is no disaster. Or amI going back to 1970's thinking again?
3-ply evaluation 7/1, 4/1 .6128/5*, 7/1. .548 1970's thinking, says Snowie. You gotta walk before you can run. Makepoints first, and don't leave a million blots. I was almost convinced.Still, with 13 checkers in the attack zone, could the blitzing play reallybe that bad? I have often been dinged by Snowie for being too conservativein positions such as this. Had to check it out.
Rollout results 8/5*, 7/1 .6027/1, 4/1 .531 A complete turnaround. The rollout indicates that the double-blot play isclearly superior. Apparently Snowie underestimated just how much groundI lose if White makes the anchor, and overestimated the cost of beinghit back. I think the key is that I am so far ahead in the race that evenif I am hit I will still have the lead. However, if White gets theanchor then White's position will play very comfortably. Snowie realizesall this, but just underestimated the extents involved.
148
173 |
| White 13
19 point match
Blue 9 |
In the old days, I might well have played the spread-them-out play of13/11*, 11/9, 6/4(2)*. After all, White has two checkers on the bar,so what bad can happen? The nine point is more valuable than the11 point, and I am almost sure to get it if I slot it.
Not any more. The bots have tought me that assets are everything.In particular, when I am short on builders it is important to grabany key point that I can. A bird in the hand is worth two in thebush. Those bad things which can't happen just might happen. I wantthat 11 point nailed down for sure.
3-ply evaluation 13/11*, 11/9*, 6/4(2)* .91713/11(2)*, 6/4(2)* .877 Not so, says Snowie. Back to the 1970's. Spread them out. Why?
Rollout results 13/11(2)*, 6/4(2)* .94013/11*, 11/9, 6/4(2)* .878 Well, that's a lot more Snowie-like. The 11 point is very valuable withthis structure of the four point made and the five point open -- almostas valuable as the nine point. That bird in the hand is worth two inthe bush. Snowie knows all this. I am at a total loss as to whyit preferred the alternative play.
136
150 |
| White 15
19 point match
Blue 14 |
I am behind in the race, and White is threatening to escape his last backchecker. In addition, White has a few threats on his side of the board.It seems natural to hit loose with 16/11, 6/4*, which conveniently unstacksmy heavy six point as well as knocking White back. It is true thatWhite has the slightly stronger board, but the other relevant bold play vs.safe play critera appear to argue for the bold play.
3-ply evaluation 16/11, 13/11 -.51016/11, 6/4* -.561 Not so, says Snowie. Just lock up that 11 point for now, play with oneblot, and see what happens. Is this right?
Rollout results 16/11, 6/4* -.52616/11, 13/11 -.549 The rollout tells another story, placing the loose hit a bit ahead ofmaking the 11 point. It is interesting that Snowie, who usually followsthe bold play vs. safe play criterion religiously, went against itsown principles for this position.
109
103 |
| White 1
7 point match
Blue 4 |
Ten years ago I would have played 7/4 without giving it a second thought.Keep the strongest board. What other consideration could there possibly be?
The bots have tought me otherwise. Builders and flexibility are what holding gamesare about. In particular, a spare on the six point is golden when theopponent has your five point. Going behind the enemy anchor is death.There is almost always a clever switching play available which will allowyou to keep your builders in front of the anchor without compromisingthe position too much. For this position, the clever play is 7/6, 4/2.That type of play has become so second-nature to me now that I made theplay without giving it any thought.
3-ply evaluation 7/4 -.3747/6, 4/2 -.420 Not this time, says Snowie. Holding the four point rather than the twopoint has priority here. I was surprised. Is there something differentabout this position?
Rollout results 7/6, 4/2 -.3877/4 -.409 The rollout vindicated me. The results were close, which was no surprisesince there can't be too much equity difference between the plays in anyevent, but the clever switching play which leaves the builder on thesix point came out ahead. What puzzles me is why Snowie chose thisposition to ignore this theme. Perhaps the fact that I have a singleblot on the other side of the board which is likely to be attacked convincedSnowie that it was more important to hold the four point in case I amhit and I hit back. There is some logic to this, but the thesis didn'tstand up to the test.
139
82 |
| White 0
7 point match
Blue 1 |
White on roll. Cube action?
Obviously White has a powerful redouble, since if he can stay on the bara couple of rolls Blue's position is likely to crack. I put a fairamount of effort into analyzing this problem, since we are talking abouta recube and I am a bit ahead in the match. It is easy to see the badscenario -- White flunks, I have to play, White flunks, and my boardbecomes history. I am not at the edge of the prime, so even if Whiteis forced to break his prime I still have a long way to go. Do I havesufficient winning chances to justify a take?
3-ply evaluation Cubeless equity: .475Redouble, pass: 1.000No redouble: .828Redouble, take: 1.018 Clearly a money take, but at the match score Snowie evaluates it as aclose pass. I wasn't convinced. The key is that if White enters atall and can't escape immediately, it is good-bye to the six-prime. Oncethe six-prime breaks he won't be able to put it together, and I will havea good chance to scramble out. Even if my board cracks a bit and I losemy six point, I will still have plenty of play with a solid four-primeand a big racing lead. It will be White who has to prove himself.And as long as I have my six point, most of White's entrances force himto crack. Was all this wishful thinking?
Rollout results Cubeless equity: .418Redouble, take: .931No Redouble: .797Redouble, pass: 1.000 It is still close, but the rollout dropped White's cubeless equity by over .05 andthat was enough to give me a take. I wouldn't call this a big error by Snowie,since its evaluation was pretty close to the rollout results. What interestedme about the position was that by applying logic, calculations, and estimations to theposition I was able to come up with the correct conclusion, while Snowiewith its general evaluation process failed. Until another giant programmingstep is made this is the area where we humans still have the edge overthe neural nets, so we better make the most of it when the right positionsarise.
143
162 |
| White 0
7 point match
Blue 3 |
When ahead in the race, race. When behind in the race, don't race. Time andtime again the bots have pounded this theme home. In this position, I ambehind in the race. 24/21 is a racing play. The blot on the 11 pointisn't in much danger, but advancing the back checker allows White toplay behind me safely while waiting to roll his eventual doubles whichwill clear the anchor and win the game. Staying back makes it difficult forWhite to find a safe play. In addition, 13/11, 6/5 both makes thepossibly valuable 11 point and unstacks the heavy six point profitably.White has no inner board, so I'm not in much danger yet of being blitzed.The advanced anchor isn't that vital. Surely there can be no questionabout this one, right?
3-ply evaluation 24/21 -.44813/11, 6/5 -.480 Wrong, says Snowie. I should dig in with the anchor and play from there.I was quite surprised. I was sure I had seen similar positions (after allthis is only the third roll of the game), and the best defense againstthe early 6-6 was usually to hang back and wait. Did I have this conceptwrong?
Rollout results 13/11, 6/5. -.44924/21 -.480 The rollout backed me up. The swing isn't huge, but it is significant. Whatis unusual is that there was such a big difference between theevaluation and the rollout for two different plays this early in the game.My experience has shown that Snowie's 3-ply evaluation and rollout resultsare almost always in agreement in the very early stages of the game.
151
149 |
| White 4
7 point match
Blue 3 |
The clock is ticking in this nearly symmetrical position. 24/23, 13/8 hasthe advantage of splitting the back men so as to give them more flexibilitytoward getting to the edge of the prime and escaping. 13/8, 6/5 has theadvantage of putting an important spare on the five point for futureboard-building. Which is more important, offense or defense?
13/8, 6/5 follows the important principle of putting my checkers whereI want them. I know that fifth checker on the six point belongs on thefive point, while the split to the enemy two point may not turn out tobe valuable. Several years ago I definitely would have played 13/8, 6/5.Hours of being beaten over the head by the bots have shown me thatthese positions need to be treated more carefully. It can be dangerousto have two checkers locked on the enemy ace point against a growing prime.I finally decided that the key factor was timing. I was ahead in therace, and after this play White would have three checkers on the midpointto my two checkers. This indicated that a priming battle would be likelyto favor White, so I should do something about that. Therefore, I optedfor the splitting play, 24/23, 13/8.
3-ply evaluation 13/8, 6/5 -.04224/23, 13/8 -.072 Wrong again, says Snowie. Offense before defense. Put your checkers wherethey belong. Will I ever learn?
Rollout results 24/23, 13/8 -.07413/8, 6/5 -.175 The rollout vindicated me big time. Not splitting is quite a blunder.Snowie fully recognizes the importance of the split, but apparently wasunable to grasp the timing considerations here. Moving the builder tothe five point was too tempting. We have seen that one of the weakestconceptual part of Snowie's game is understanding timing considerations.Unfortunately, it is often the weakest part of a human's game also.
140
140 |
| White 4
7 point match
Blue 3 |
This is the same game a couple of moves later, after both sides have madesome improvements. Now I must choose between running with 22/13 andbringing builders down with 13/10, 13/7. In the old days, there wasno way I would break that anchor. Much too dangerous. Better to bringdown some badly needed ammo to build my own board. I'll roll that sixwhen I need it.
The bots have told me time and time again how wrong this is. Sixes justdon't grow on trees. Get that checker out while you can. Don't beafraid to leave the anchor -- the bad guy can't both prime you and attackyou at the same time. And so on, and so on. My training had toughtme to play 22/13.
As I was reaching for the checker on the 22 point, I had second thoughts.Fours and fives were White's worst numbers -- why should I make them goodfor White? I had spares to play with and attacking possibilities, soI wouldn't have to spring a back checker so quickly. It is White whohas the stronger inner board -- I don't want to get battered around.My attack force is awkward -- I need builders to improve my inner board.After all this thinking, I finally changed my mind and played 13/10, 13/7.
3-ply evaluation 22/13 -.07913/10, 13/7 -.194 Yep, another blunder. When will I ever learn? It seemed almost pointlessto roll this one out, but just to kick myself in the head again ...
Rollout results 13/10, 13/7 -.08922/13 -.092 Wait a minute! Not so clear. The rollout has the two playsas about equal. Maybe there was a method to my thinking (madness?) afterall. I can understand Snowie liking the thematic run. Apparentlyit failed to weigh in the importance of offensive builders here. If Ican build another inner board point before White escapes, I may not haveto worry about a priming battle.
117
102 |
| White 0
7 point match
Blue 1 |
This one seemed easy enough. I know I want my three point, so let's makeit. Sure I am leaving a few more shot numbers, but at least many ofthese hitters come into range of my checkers on White's bar point so I will havereturn shots. Sure I leave more hit and cover numbers, but even that Ican live with. Also, staying on the midpoint allows me to potentiallylink there if I roll a five next turn, while 13/8 splits my outfield resourcesinto two. Communicate! Seems like a no-brainer.
3-ply evaluation 13/8 +.0426/3, 5/3 -.058 A blunder? Now that is hard to believe. Why? That didn't make much senseto me. I anxiously awaited the rollout results on this one.
Rollout results 6/3, 5/3 -.00613/8 -.047 Now that's more like it! Human logic and intuition clearly won outhere. Frankly, I can't see any reason why Snowie downgraded making thethree point so badly. Perhaps the loss of spares on the five and six points.Perhaps Snowie was overly impressed by the few extra hit and cover numbers.Perhaps Snowie failed to recognize the importance of potentially being ableto make the midpoint and bring the checkers around together. This isn't likeSnowie, as I have seen in the past it understands these concepts quite well.Something just went wrong here. I wonder if the fact that White didn't ownhis six point somehow caused Snowie's evaluator to go haywire, since mostof the contact positions in Snowie's training involve both sides owning theirsix point.
116
139 |
| White 4
7 point match
Blue 6 |
Note the match score -- that may be relevant here. I can't use a gammon,but my opponent can. I have the choice between leaving my anchor with20/14(2), 7/1(2) or holding the anchor and playing the cramped 14/2, 7/1(2).The race is now close. My racing chances aren't great holding the anchor,but I may be able to scramble the back man out and over in time for a race.If I leave the anchor, the back checker is stranded -- with more gammon danger.White could easily build a full prime and walk it home. Holding the anchorseemed clear.
3-ply evaluation 20/14(2), 7/1(2) -.38814/2, 7/1(2) -.451 Snowie dinged me rather harshly for not getting out when the gettingis good. I found that a bid hard to swallow. Sure my play leavesmy position somewhat cramped, but to just leave the back checkerstranded? Granted White will have to use his next roll to get his backchecker safe, but after that he will be free to roll the prime home.
Rollout results 20/14(2), 7/1(2) -.48814/2, 7/1(2) -.488 Well at least that makes more sense -- the plays came out even. I stillthink that holding the anchor has to be better, but the idea thatleaving the anchor was way better was hard to believe.
91
92 |
| White 5
7 point match
Blue 3 |
Blue on roll. Cube action?
At this match score, White can take very aggressively in non-gammonishpositions. From White's point of view:
White passes: Ahead 5-4 (2 away, 3 away), 60% equity.
White takes and wins: Wins match, 100% equity
White takes and loses: 5-5, 50% equity.
White is risking 10% equity to gain 40% equity, so he is getting 4 to 1odds on his take if there are no gammons. This position isn't quitegammon free, but there is very little gammon risk. White certainlyhas enough winning chances to take, with the combination of winningthe race and hitting a shot. The real question is whether I should turnthe cube. It a matter of market loss. If I make my four point, willI lose my market? If yes, I should double. If no, I should wait. Ithought yes.
3-ply evaluation Cubeless equity: .464No double: .722Double, take .697Double, pass 1.000 Snowie didn't think it was a double, which obviously means that Snowiedidn't think it was a market loss if I make the four point. I wasn'tconvinced. White is going to have a tough time winning if I make myfour point.
Rollout results Cubeless equity: .540Double, take: .897No double: .865Double, pass 1.000 The rollout said otherwise. Note the big change in cubeless equity -- itwent from .464 to .540. That was enough to convince Snowie that I hadthe market losers. I have no idea why Snowie evaluated White's positionso highly. Yes three-point games always have a lot of play, but thisseems to be carrying the theme to an extreme.
108
107 |
| White 0
11 point match
Blue 0 |
The age-old problem of whether or not to break an anchor. It certainly mustbe right to make the three point in all variations, so I will playeither 11/7, 6/3 or 22/18, 6/3. I used to be paranoid about breakingan anchor. Not any more. The bots have tought me otherwise. It is oftenbetter to make a run for it than to find yourself getting stuck on ananchor forever. What are the conditions here? I am ahead in the race.I have by far the stronger board. White has that blot on his ace point,so my blots will be almost immune if I play 22/18, 6/3. I am blocked onsixes where I am now, so if I don't move from the 22 point I may have adifficult time freeing the back men later. White's position is likely toimprove, while mine can only get worse. How many more arguments do I needto break the anchor? I played 22/18, 6/3 with complete confidence.
3-ply evaluation 11/7, 6/3 -.49922/18, 6/3 -.588 What is this? Breaking the anchor is a blunder? This went againsteverything I had learned. As you can imagine, I was very eager to seethe rollout results on this one.
Rollout results 22/18, 6/3. -.48811/7, 6/3` -.599 Yep, there was a blunder to be made. But the blunder wasn't breaking theanchor -- it was holding the anchor! This is about a big a turnaroundas I have ever seen from the 3-ply evaluation to a rollout for a relativelynormal position. I am at a complete loss as to where Snowie got itsevaluation. Obviously it thought my winning chances holding the anchorare better than they actually are -- we have already seen that from thecube decision of the previous position which is a relatively similar position.However, it would take more than that to produce this kind of monstrousturnaround. It is just baffling.
132
103 |
| White 1
11 point match
Blue 0 |
How ugly is ugly? In the old days, a play like 8/2, 6/3 would be laughedat. The bots have shown us that sometimes ugliness is beautiful, andthat super-safe pay-me-later ugly plays are often correct. But can itbe correct here? Stripping both the eight point and the six point,putting a checker on the three point out of play, and leaving a bloton the two point which is difficult to cover? No way! 13/4* keeps aperfectly balanced position, and at least has some real upside if I'mnot hit back. White has a strong board, but his three point is still openso getting hit back isn't necessarily fatal. If I delay White may close thatthree point, and then getting hit will be completely fatal. It must beright to pay now, right?
3-ply evaluation 8/2, 6/3 .18513/4* .126 Not so, says Snowie. Ugly is beautiful. Well, it sure seemed ugly tome. Let's see how ugly a rollout thinks it is.
Rollout results 13/4* .1268/2, 6/3 .088 Another turnaround. It is interesting that the equity after 13/4* agreedexactly with the 3-ply estimate, but the equity for 8/2, 6/3 dropped almost.100. Ugly isn't so beautiful after all.
119
100 |
| White 1
11 point match
Blue 0 |
In a continuation of the same game after some scrambling this pay me nowor pay me later position arose. It sure looked right to me to paynow with 14/10, 13/9(3). I would be virtually gin if I survived.White's board, while strong now, would only be getting stronger in thenext few rolls. If I paid later with 14/6, 13/5, my position would becompletely stripped and I would be very likely to have to leave a shotin the near future anyway. I wouldn't have time to wait around for myeventual doubles. A classic example of when to pay now.
3-ply evaluation 14/6, 13/5 .24614/10, 13/9(3) .224 Snowie thought the plays fairly close, but definitely want for paying later.This had to be suspect. All the relevant factors pointed towards payingnow.
Rollout results 14/10, 13/9(3) .28914/6, 13/5 .197 As I had thought. The rollout results indicate that paying later is abig blunder. This seemed quite clear to me at the time. Snowie is usuallydeadly accurate on pay-me-now or pay-me-later decisions, and this onelooks like a run-of-the-mill example. I have no idea why Snowie gotthis position so wrong.
154
210 |
| White 0
11 point match
Blue 3 |
White on roll. Cube action?
While Snowie plays backgames better than most people think, it doesn't evaluatethem very well. I had no difficult taking in the above position; in fact,I doubt very much if White should have doubled. However:
3-ply evaluation Cubeless equity: .601Double, pass: 1.000No double: .929Double, take: 1.096 Snowie evaluates this as a moderate pass. I don't believe a word of it.This is one position where I would be confident betting againstSnowie's judgment. My position simply has too much play if handledcorrectly.
Rollout results Cubeless equity: .505Double, take: .859No double .807Double, pass 1.000 A drop of almost .100 in equity for White's side, making it an easy take.And this is only on a 2-ply rollout. This is the sort of positionSnowie plays the backgame side considerably better with a 3-ply rollout.It wouldn't surprise me if the 3-ply rollout indicated that it wasn't evena double. However, if you were playing against Snowie 3-ply, you couldhave stolen a point.
153
195 |
| White 3
11 point match
Blue 3 |
One thing which the bots have taught me is that even when playing a backgameor a likely backgame it isn't a good idea to have checkers needlessly sent back.You can't afford to run short of men up front, or you won't be able tobuild a strong board quickly. While the choice of plays here didn't figureto be too important, leaving unnecessary blots in my outer board withsomething like 20/14 didn't seem right. More accurate appeared to play20/18, 7/3, at least starting the next inner board point in line ratherthan throwing the checkers to the wolves.
3-ply evaluation 20/14 -.49520/18, 7/3 -.578 Much to my surprise, Snowie thinks 20/14 is far better than my choice.Perhaps it is the duplication of twos, or perhaps the extra outfieldpresence and the improved possibility of making the eight point or thebar point. I was rather surprised. 20/14 is the sort of play I used tomake, but I have learned to avoid that approach. Now Snowie is tellingme that it is far better than the more conservative approach. This isa pretty big statement by Snowie, particularly since this is the sort ofposition where it isn't likely to matter too much what you do because youwill probably wind up with a good 1-5 structure or something like thatwhatever happens.
Rollout results 20/18, 7/3 -.47820/14 -.528 Well, the rollout found my play to be superior. I'm not exactly sure whetherthat means too much in this type of position, but it certainly puts toquestion Snowie's claim that 20/14 is far better.
115
106 |
| White 5
11 point match
Blue 4 |
In my youthful days I'm sure I would have unhesitatingly played 10/1*.Go for the throat! What blockade? I can leap that little thing withone easy bound. This is gammon city. What can possibly go wrong?
Now that I am older and (hopefully) wiser, having been dinged by thebots countless times for plays such as this, I know better. There isa lot which can go wrong. 4-4, 3-3, and 4-3 are legal rolls. Or Whitemight hit back, and I might enter with some prime busting number -- youknow when a little 2-1 or 1-1 busts your prime you have a lot of bad numbersfloating around. 21/15, 10/7 is clear. It will be very hard for theroof to cave in, and I will still have plenty of opportunities to winthe gammon.
3-ply evaluation 10/1* .92121/15, 10/7 .914 Snowie thought the plays close, but believed that the extra gammons fromthe loose hit were sufficient to justify the play. Even though I wasn'tdinged for a big error, I thought this was worth rolling out becauseI was convinced that Snowie was way out to lunch.
Rollout results 21/15, 10/7 1.05210/1* .858 I was not disappointed in the rollout. Snowie's choice, which it wouldhave made had it actually been playing, was almost a double whopper.We have seen that Snowie can have difficulties with timing considerations,but this one is pretty extreme. What is surprising is that Snowieis usually quite sensitive to the dangers of getting stuck and beingforced to break the board. Here, the combination of the gammon potentialand the false sense of security lulled Snowie into an awful play.
No doubt many of you readers have collections of similar Snowie blackouts.It might be a worthwhile idea to put them all together and see if we canform some idea about the types of positions where Snowie is likely tofalter. In the meantime, remember that Snowie is not infallible. EvenGod can be wrong.
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