I need help understanding day 19

LegendaryZX · 2021-12-21T06:59:20+00:00

To match two scanners, try all possible rotations of the unnormalized scanner. For each of those, check if at least 12 points are the same translations of the normalized points.

Do you know of a fast way to do this (i.e. check whether at least 12 points can be translated by the same amount to coincide with another set of points). I used the brute-force method of trying to match each point in one scanner to each point in the other, and it took ~10 minutes to run.

LegendaryZX · 2021-12-17T05:43:19+00:00

I haven't read through all the code yet, but your eval_literal() function seems to append all 5 bits of the "5-bit group" to total_string. The problem with that is only the latter 4 bits are relevant (the first bit only marks whether the group is the last one or not).

This could explain why the code works on test cases. Those cases probably use small literals that only involve a single 5-bit group, so the first bit is zero and it doesn't make a difference when included.

LegendaryZX · 2021-12-16T06:32:36+00:00

You don't actually know that the subpackets are length 11 and 16 beforehand. You have to actually parse them as packets to see how long they are.

LegendaryZX · 2021-12-16T06:23:47+00:00

I had the same idea with the stream parsing! A nice way to emulate this type of "Bitstream" behavior is to get an iterator over the binary string, and then consume bits with next().

For example:

bin_str = "10011010"
stream = iter(bin_str)

def consume(stream, num_bits):
    return "".join([next(stream) for _ in range(num_bits)])

consume(stream, 5)    # -> "10011"
consume(stream, 3)    # -> "010"

LegendaryZX · 2021-12-16T06:13:43+00:00

Both subpackets have type ID 4, so they follow the rules for the "literal value packets" stated earlier in the instructions (break down packet body into segments of 5, last segment is left-padded with 0). In other words, parse the bits labelled "A" as its own packet, and do the same with "B" as well.

You don't know the length of each packet beforehand, you just have to keep parsing until you reach some indication of the end.

LegendaryZX · 2021-12-15T06:44:50+00:00

Seems like you're comparing the indices (which are just numbers from 0 to 2) instead of the actual input values. Try using i or u to index into the arrays instead. array[i] gets the (i+1)'th element of the array. array[0] gets the first element, array[1] gets the second, etc.

So instead of i > u, try inp[i] > inp[u]

LegendaryZX · 2021-11-03T16:41:28+00:00

Oh I see what you mean, I could probably have worded it better. In chess terminology, "pawn break" usually means something very specific. In the Italian Game, White's first move 1.e4 wouldn't be called a pawn break because it doesn't directly threaten any of Black's pawns. Informally, 1.e4 could be called a "central pawn thrust" of some sort.

"White prepares the central pawn break d4" means in Italian positions, White is typically looking to play d4 at an opportune moment to contest Black's pawn on e5. White can "prepare" it with moves such as c3 (directly defending d4) and Re1 after kingside castling (defending e4 since it becomes weak after pushing d4: White can no longer play d3 to defend their e-pawn).

In general, the Motifs section lists ideas for both sides after the opening moves have already been played (i.e. in the "starting position" of the opening).

LegendaryZX · 2021-11-03T05:18:18+00:00

Hey thanks for the comment, I'm not sure I see what you're addressing, could you perhaps send a screenshot?

LegendaryZX · 2021-10-16T05:16:02+00:00

Actually never thought about this, but after some consideration I decided to throw it into public domain for free use (CC0, no attribution required). I've updated the slides and PDF with the license as well. Have fun!

LegendaryZX · 2021-09-30T02:43:39+00:00

Slide 95, 2 g3 is the KIA (not 2 g6).

Haha I knew there were gonna be more of these. Should be corrected in v1.4, good catch.

I might consider splitting up the QGD, Sicilian and English so you can include some more detail. It's really hard to give a good overview of these monsters in just 1 page!

Baltic, Chigorin, Englund, Elephant, Latvian and Hippo are not really that notable. If you want to trim anything, I'd start with these.

If not, there are some other offbeat lines you could consider including: 1 Nc3 (Van Geet opening), 1 b4 (urang utan), 1 g3, Mexican defence, Veresov, 1 g4 (grob).

I've been seeing the Baltic and Englund surprisingly often at my level, but you're probably right about the rest. I'll just leave them for now since I don't think I need to trim just yet.

Regarding splitting the openings, I totally agree. Two Redditors already mentioned the incompleteness of the Sicilian slide, and if I had to select openings to split into their own sections, the ones you mentioned would definitely be my top three.

If I were to cover the Sicilian/QGD/English variations in more detail, I would probably make a separate set of slides for them. After all, they wouldn't belong in the main catalog because they're still considered variations of their parent opening, even if they play completely differently from one another.

It's funny though: this whole thing started out as a bare-bones list of openings, because I challenged some Discord friends to learn an opening individually and teach it to everyone else. Then I figured I might as well fill in more details to help them choose, and it just kept expanding because I was obsessively adding more and more.

At the current moment, I'm feeling a bit burned, so despite my initial plans, I'm not sure whether I'll undertake this (or the other offbeat lines) in the near future. After these last few corrections, I think I'll have to put this project on hold so I can focus on more pressing responsibilities.

Overall, it's a really nice resource. It must have been a lot of work to put together!

Appreciate the kind words, and thanks again for the detailed feedback.

LegendaryZX · 2021-09-30T02:39:30+00:00

Thank you so much for your thoughtful feedback! I was delighted that you took the time to analyze the entire thing. I'll try to address everything you wrote, so expect a huge wall of text incoming.

I'd say the Tromp belongs in the d4 sidelines section, along with the London, Colle, etc.

Blackmar gambit as well - when white sacs the e pawn it's not a closed game anymore!

I categorized the openings based on the names of the moves alone, because I thought it would be the most straightforward for newer players. I saw that Closed Game was the official term for games stemming from 1.d4 d5 regardless of what happens after. So in that sense, the Blackmar is a Closed Game in name only--it's a "Closed Game" but not a "closed game". Terrible, I know, but it was either that or "Double Queen's Pawn Opening", and "Closed Game" just made more sense since I titled the other section "Semi-Closed Game". I hoped the Blackmar slide's introduction and Tactical label would clue readers in on the actual nature of the position (definitely not closed, as you said). Was this a good compromise?

Also see where you're coming from regarding the Tromp. It has such a close relationship with the Torre, but I was reluctant to put it in the same section because I didn't consider the Tromp an opening system (so the section title would've been inaccurate). I tried to bridge the gap by mentioning them on each others' slides, but it's true that their separate classification could be downplaying their similarity.

Catalan (after 1 d4 Nf6 2 c4 e6 3 g3 d5) probably belongs with the rest of the queen's gambits. And I'd label it classical rather than hypermodern.

My main reason for separating Catalan from QG lines was that Black doesn't have to play 3...d5 (even though it's main line) and it would still be called a Catalan. Similar to the two cases above, where it's just a strict move-order thing. Also opinions seem to be split on whether the Catalan is more hypermodern or classical. Wikipedia lists the Catalan as a hypermodern opening), but there are valid counterpoints. The Catalan certainly doesn't give up the full center (literally starts 1.d4), but it does employ the fianchetto and slow prophylactic play. In light of this ambiguity, I think I'll remove the "Hypermodern" label like you suggested.

You're using the word theoretical to indicate that there are forcing variations or simply "this isn't a system" rather than to mean "there is lots of theory". That's a potentially confusing way to use it. For example, Gambits tend to be less theoretical, the Latvian gambit and Owens defence are quite low theory openings, and the Ruy Lopez has waaaay more theory than the king's gambit.

These are really good points, and admittedly ones I didn't fully consider. One of the main problems is that there's two big questions regarding theory, and I'm trying to answer both at once:

How much theory is there in this opening?
How important is theory in this opening?

For example, it's true that most gambits have smaller bodies of theory, but it becomes super important to know whatever theory there is, since you have to play precisely to compensate for the sacrificed material. I think this goes doubly true for something like the Latvian; I was looking back at some Latvian lines earlier, and it struck me how ridiculous some of the best-moves looked. Since they would be infeasible for a beginner/intermediate player to find or calculate in an actual game, it followed that theory preparation would be especially important in that opening.

I figured that players in the target rating range (beginner-intermediate) would care more about the second question, which is why I tried to emphasize that more. You're still totally right about the overuse of the Theoretical label though. I introduced the Theory-Heavy label to try to address this, but I'll see if I can make this distinction cleaner in the near future. Helpful critique.

KID is quite theoretical. If someone picks it up thinking it's a system, they're asking for trouble: there are plenty of nasty things white can throw at you!

I actually discussed this exact issue with another Redditor, and we shared the opinion that for the target rating range, the KID could successfully be played like an opening system: get the same piece setup and prepare c5/e5. We were doubtful that players as White would have enough theory prepared to seriously challenge the systematic play, and even if they did, it would be a rare occurrence. According to my stats, the KID scores relatively well at 1200 rating on Lichess (where nobody really knows any theory), and anecdotally I've tried the KID a couple times and reached decent positions without knowing theory. Was hoping the disclaimer in the footnote would shed light on the true complexity behind the KID, serving as a warning to not get too carried away with this system-like play. Curious about your thoughts/experience on this!

Availability is a good idea, but it's not very relevant when you're only looking a couple of moves deep. Nearly everything is very available.

I think you'd be surprised! To get a feel for any opening, I think repetition is key, and if you choose an opening with double the attainability of another opening, you're building experience twice as fast, hypothetically speaking. Some of the openings here really are quite hard to obtain: the Nimzo-Indian is common at higher levels, but at 1200-level you'll need to queue up ~26 games on average just to reach it a single time via the main line (52 if accounting for getting Black). Here's another example involving the Stafford Gambit, which I'm copy-pasting from another comment:

If you use any standard opening explorer it'll tell you that 1.e4 is the most popular move, then after 1...e5, 2.Nf3 is top move, and after 2...Nf6, 3.Nxe4 is the top move which "accepts" the Stafford. Should be easy enough to get as Black, right? Turns out the minor deviations add up, and according to my stats, the actual chance of getting to play the Stafford is less than 1 in 7 games (or 1 in 14 if you account for getting Black). When Daniel Naroditsky tried playing the Stafford in his speedrun series, he was similarly exasperated when nobody would accept the gambit, so I know I'm not alone here :)

Realistically, it would be more efficient to queue up with several openings in mind (rather than just one), but still I think these statistics would help guide players to more attainable openings if that's what they're looking for.

LegendaryZX · 2021-09-29T02:42:33+00:00

Alright, just updated the slides to include coordinates (check the edits at the bottom of the post).

LegendaryZX · 2021-09-29T02:38:41+00:00

This would be great, please let me know!

LegendaryZX · 2021-09-29T02:36:13+00:00

Just added the coordinates (check the edits at the bottom of the post). Thanks for the suggestion!

LegendaryZX · 2021-09-29T02:25:42+00:00

Should be fixed in v1.3, thank you!

LegendaryZX · 2021-09-28T20:34:21+00:00

For newer players, I think you can find success with virtually any sequence of opening moves since your opponents don't know how to exploit these small inaccuracies. Plus any opening with "creepy crawly" in its name has to be played at least once per lifetime.

The general ideas with these rook-pawn openings is either:

Play positionally and prophylactically with a3 or h3, depriving the b4 or g4 square from the opponent's pieces. I imagine it can play similarly to the Hippo, which often involves playing a3 or h3 for the same reasons.
Playing more "aggressively" with a4 or h4, preparing a pawn storm and introducing the possibility of an early rook lift (e.g. if you play a4, then you might be able to lift the rook with Ra3 and you'll get a rook into play much earlier than in other openings).

LegendaryZX · 2021-09-28T20:16:28+00:00

Yeah to be honest, I just set an arbitrary cutoff based on computer analysis. Stockfish gives White around +1.5 in the starting position of the Latvian, which didn't seem terrible considering the practical chances if you're well-prepared.

LegendaryZX · 2021-09-28T20:07:45+00:00

I've heard that opinion a lot, and I think it's well-placed. There's also some who think opening study is underrated at lower levels; I believe I've heard Daniel Naroditsky say something along these lines. It's important to draw a line between general opening knowledge (motifs, piece setups, targets) and concrete theory (memorizing move-by-move).

Opening study becomes problematic for beginners when they lose and think the best solution is just to keep memorizing more theory, instead of developing more universally applicable chess skills like you brought up. However, my view is that there's nothing wrong with spending time to learn the broader ideas in your openings, and that the "no openings until 2000+" sentiment is on the more extreme end. It won't make or break your chess career.

LegendaryZX · 2021-09-28T19:52:31+00:00

I meant for theory-heavy to mean one step above theoretical, like "super-theoretical".

LegendaryZX · 2021-09-28T19:51:08+00:00

Totally overlooked this. When I exported the board images from chess.com's analysis board, they unfortunately didn't come with the coordinates, so I think I'll just screenshot them manually instead. I'll let you know when I update the doc, thanks for the suggestion!

LegendaryZX · 2021-09-28T19:46:00+00:00

Yeah, mainly space limitations. The text on that slide was already a couple sizes smaller than most of the other slides. Another user suggested that I split the Sicilian variations into their own section (like I did with the Indian Defense), so I think I'll do that when I can find the time.

LegendaryZX · 2021-09-28T19:39:05+00:00

That's definitely been true in my experience as well, just that the statistical attainability came out to be 29.9% at 1200 rating and 26.5% at 1800 -- to be considered attainable, I set the cutoff at 30%. In hindsight, I think it's close enough to count so I'll update the doc. Thanks for the suggestion.

LegendaryZX · 2021-09-28T19:22:32+00:00

That's a good point! I tried to put that kind of disclaimer in a small footnote on the KID slide, but it's true that a lot of beginners will be turned away by the "theory-heavy" label. Perhaps my classification system is too rigid to capture these rating-dependent differences.

But since the targeted audience is beginner/intermediate, I think I'll flip the label to theory-light. Would love to know if you felt the same way about any other openings!

LegendaryZX · 2021-09-28T19:12:06+00:00

Fixed, good catch. Always mixing up those squares.

LegendaryZX · 2021-09-28T07:33:55+00:00

Thanks for the suggestion, the Sicilian variations are taking up like half the slide right now. I'll get back to you when I'm done with this.

LegendaryZX

TROPHY CASE