tl;dr I betrayed the CloneBot clique and submitted MimicBot. My submission is in this Github repository.

My Process in chronological order:

There were three important things I noted in the original post

• Self cooperation is free, so an early lead is a big advantage.
• There are guaranteed to be “silly” bots in the early pool.
• You can vary your strategy depending on the round.

It seemed to me that the best strategy was to get as many points as possible early by exploiting silly bots, cooperating with anyone willing to cooperate, and folding somewhat to attackers. Then later on just play a non-exploitable cooperative strategy and hope for your early advantage to snowball.

Simulation

After seeing AbstractSpyTreeBot and some of the comments around it, it seemed to me that simulation was perhaps the best way to take advantage of simple bots. There are various approaches you could take, but mine was to simulate every possible sequence of moves I could make for the next N turns, and use the one with the best outcome. Since this has exponential time complexity, I only considered the moves 2 and 3 and kept N fairly small, with the option for the game runner to reduce it further to improve performance.

There are several possible pitfalls with simulators:

• The opponent might have randomized behavior, making your simulated predictions useless. In fact, not using randomization seems wrong to me, since you might get stuck in a rut against another deterministic bot, alternating 2 and 3 on the same schedule. Only bad bots would be deterministic and therefore simulatable.
• The opponent might have planted a landmine in their code to disqualify any potential simulator.
• The opponent might be slow, and make my dozens of simulations per turn take too long.
• The opponent might be a BullyBot, who attacks until the opponent retaliates. My short time horizon would make folding look correct, when actually retaliating would give more points in the long run. At the same time, I did want to fold against AttackBot.

My solution to the first three problems was to only run simulations against bots with two or fewer open parentheses “(” in their source. That’s how many you need to define __init__ and move, so it wouldn’t leave any for calls to exec or random or inspect. I suspect it might be possible to sneak a landmine past this requirement, but since I didn’t tell anyone what I was doing it seemed safe enough. Hopefully enough of the deterministic bots fulfill this requirement for simulation to be worthwhile.

For the BullyBot problem, I had the simulation also see what the best strategy was that didn’t let the opponent outscore by more than X but also got at least Y points. If this strategy didn’t exist, such as against AttackBot, I would fold, but otherwise I would play that strategy. I also made the simulation be more willing to be uncompromising against attackers as the rounds went on, in case one of the dumb bots was actually putting up a fight in the overall tournament.

For my backup strategy against non-simulatable bots I kept it simple and pulled from Zvi’s playbook. In the early rounds, I play an EquityBot which folds if the opponent plays 3 ten times in a row. In the later rounds, I play DefenseBot.

I considered a plan of obfuscating my code so that it would look safe to other simulators, and then disqualifying them if they tried to simulate me. I gave up on that because it seemed like other simulators would either be careful like I was or someone else would disqualify them for me. Plus, simulators are fun. I’d rather have a fair fight against other simulators. My code uses randomization and has lots of scary keywords in it, so other simulators aren’t going to be exploiting me.

To feed my simulation plan, I found two people who didn't have time to make a proper submission, and got them to submit PasswordBot, which plays 3 on the first two turns, then if the opponent played 2 on the first two turns it plays 2 for the rest of the game, and otherwise plays 3 for the rest of the game. I figured that only a branching simulator could take advantage of this.

CloneBot

Throughout the week, a couple people publicly announced intent to join the CloneBot clique. I decided that the CloneBots would be a huge threat that I might not be able to compete with if I didn’t do something to address them. Originally I was planning to not contact the clique and use the public source, but when Vanilla_cabs announced the source would not be public, I messaged them indicating willingness to join the clique. I’m not sure how suspicious the timing seemed to them, but I was included anyway. I gave Vanilla_cabs some notes about other parts of the code, but intentionally did not comment on anything related to security.

My plan was to bypass whatever they were using to check that the opponent is a clone, so that I could get perfect cooperation with clones, but also use my simulation strategy to exploit dumb bots and continue to cooperate with outsiders as the clones got more aggressive.

On Friday, the CloneBot security update was released, with the final version of the clone check.

(I can't figure out how to paste code into here), the source is here.

There are two constraints:

• After the string sanitization, my code before the payload must compare identical with the sanitized version of my opponent’s pre-payload code.
• After the string sanitization, my code after the payload must have at least eight spaces at the beginning of every line.

I got cracking.

I noticed that the checker was splitting the code by “\n”, so I wondered if there was any other character that python would treat as semantically equivalent to a newline. There is - the ASCII Form Feed character \f (0x0C). However, this didn’t work. I hadn’t noticed the earlier sanitization step of using splitlines() and then joining by \n. All my \f’s were just getting turned into \n’s and getting busted.

I then wondered if there was any other way of convincing python that there was a newline, or convincing it to dedent to a lower indentation level, without using a character that would be caught by splitlines or using less than eight spaces of indentation. A string of google searches led me to reading through the C code for the python lexer, which was very educational but convinced me that this route was a dead end.

I noticed in reading about the lexer that it has a somewhat complicated system for handling tabs and spaces in indents. I noticed that the code sanitization was automatically converting tabs to four spaces and wondered if I could use a mixture of tabs and spaces in indentation to manipulate the if / else statements in the clonebot move function to make it run the payload early. Unfortunately python 3 does not allow any mixture of tabs and spaces which makes the meaning of the code depend on how many spaces a tab is worth. I think this attack vector might be valid if we were using python 2.

At this point it was 3 AM and I slept on it. On Saturday morning I thought back to the very thing that had foiled my first attempt, the splitlines() sanitization. Instead of finding a character that would be treated as a newline but not caught by splitlines, what about a character that would be caught by splitlines but not treated as a newline? I found a thread online where people were complaining about splitlines splitting on certain characters, and a dev said the behavior was intentional. One of those characters was 0x1D, the ASCII Group Separator character. I tried it in a test program, and it worked. I tried it in CloneBot, and… it worked!

That’s the technique my final program uses. Starting with the first comment in the move function, I replaced every newline with 0x1D, which is a valid character in a comment. The bottom half of the CloneBot source is a comment and gets skipped over, so the move function actually runs my custom code, which is all indented at least eight spaces and fulfills the second constraint of the clone check. I use the same cooperateWithClone function as the clones to cooperate with them until the showdown round, at which point I just treat them like any other bot.

I’m not too surprised that other people tried and failed to cheat the restrictions, since it took me 8+ hours and some real thinking outside the box. It does make me feel better that I’m not the only would-be betrayer.

Predictions

How do I think I’m going to do? My bot passes the clone check both in Vanilla_cabs’s official checking tool and in my test harness, but I can see some possibility of something introducing enough differences to screw up the check. Vanilla_cabs encouraged people to submit through the form, while I submitted a git repo. Lsusr promised to preserve my special characters, but the real game environment might be different enough to make the check go wrong, though if that was the case maybe all clones would fail the check.

Separately, my bot is pretty complicated. I wouldn’t be surprised if it was the longest submitted, at over 250 lines of code. I’ve done a fair amount of testing, but I am not confident in my ability to make my software robust to anything that might happen. There’s a decent chance something unexpected will happen and I’ll crash and get disqualified.

However, if my bot doesn’t have a crippling bug and no one else figured out how to submit a MimicBot, I don’t really see how I lose. I get lots of points from clones, dumb bots, and cooperators, while everyone else is losing out against at least one of those.

I’ll say 30% my bot crashes or fails the clone test, 10% someone else submitted MimicBot and theirs is better, 10% those things don’t happen but I still lose, 50% I win.

Free self recognition seems like it makes game less interesting, And that anyone who gets a big lead early just wins?

Is reading the opponent's source code legal?

from extra import get_opponent_source

class SpyBot():
    def __init__(self, round=1):
        self.round = round
    def move(self, previous=None):
        opponent_source = get_opponent_source(self) # return value is of class `str`
        if '3' in opponent_source:
            return 2
        return 3

If you're participating in the contest and you want to win, I have a proposition for you:

Howdy! You've probably looked up Zvi's past Darwin game [? · GW] that directly inspired this one. A group of players formed a clique who recognized each other, cooperated among themselves and defected on everyone else. They nearly wiped the board, but they were preyed upon by a member who played both sides.

What they missed was a way to guarantee that all members apply the decided strategy. They had no way to enforce it.

But we have a way.

I call it CloneBot: a bot who checks that its opponent has the exact same code as itself. No way to cheat that! It guarantees that every member of the clique does the same thing. Moreover, there'll be a way to cooperate optimally, avoiding losing the first rounds to coordinate. The clique are gonna be the most efficient ccoperators.

But in the end we're all gonna tie, it's boring. I want to take a chance at winning!

So do I. This is why the clique are only going to collaborate until a predefined round. After we've eliminated the competition, we can have a dramatic showdown among ourselves. Cool, no? In the code, there's gonna be a separate function that's called only after a given round. The code checker will verify that the function is only called at the right time, but will ignore what is inside.

What will CloneBot do?

Depends on the proportion of clones. If we're a big group, CloneBot will straight up defect against outsiders by playing 3. Otherwise, CloneBot will cooperate, but make sure opponent does not gain more than itself.

With its clones, CloneBot will cooperate by alternating 2-3. Who gets the first 3 will be determined fairly before the first turn starts.

Ok, but I don't want to find myself in a small clique that's going to lose.

You don't have to commit to submitting CloneBot right away. All you need to do is contact me to say you're in, conditional on the clique being large enough. By default, contact me privately. If you want, you can roll a D6, and if you roll 6, join me publicly right here.

A few days before the deadline, if we're 5 or less, I'll just announce that the critical mass was not reached. But if we're more than 5, I will make public the names of all who contacted me to join the group and crush the competition. If I post your name at that moment, you must submit CloneBot.

I like the idea, but I wish X instead of Y.

Every detail is open to discussion for about 3 days. After that, this post will be updated, and every person who expressed their desire to join will be informed of the changes and asked to confirm their participation.

Where do I find CloneBot?

 I'm considering making the code public.

Let the best clique member win :)

Explanation of my strategy and thought process in chronological order

After seeing Vanilla_Cabs's comment I lied to them about wanting to join the clique. I was undecided, but I figured seeing the code of the clique can be a great advantage if I can exploit some coding mistake and I can still decide to join later anyway if I want.

The first versions of CloneBot (the name of the program for our clique) did actually contain a mistake I could exploit (by defining the __new__() method of the class after the payload) and so this was my plan until Vanilla_Cabs fixed this mistake. After they fixed it, I didn't notice any way I can take advantage, so I joined the clique in spirit.

Initially my plan for my bot was a simulator which simulates between 100 and 1000 turns of the opponent against a few candidate bots (ZviBot, TiTforTat, return 3, return 2, etc..) and then depending on the round number either chooses the one with the maximum point for me or the one which gets more points than the opponent. There were unfortunately two problems with this plan:

1. Bots who can detect if they are in a simulation can get me into an infinite loop which would disqualify my program, so I had to research the ways this might happen to know how to prevent it. I started by inspecting the code for AbstractTreeSpyBot and I did notice some ways to do this:
   • The code always instantiates a new object, so by storing past moves, I can detect if I'm in a simulation if my move() method's argument is not None and I have not stored previous moves. This defect however is really specific to this program and other simulators can easily avoid it by storing the instantiated class object between rounds.
   • The code simply calls the simulated bot's move() method which can be detected by inspecting the call stack and finding a local variable named 'self' with a method named 'move' of a class type not named the simulated bot's classname. This method of detection can still be tricked by running the simulation in a different process (eg by calling the python interpreter from the shell, this has the advantage of having an easy and robust way to redefine get_opponent_source()), but still I expect this would DQ many submitted simulators. (I attached the code of a bot using this type of detection.)
2. Isusr posted a very unforgiving time limit. Unfortunately, I could not make simulator bot work in this timelimit. In fact, on my laptop even AbstractSpyTreeBot does not run in 0.05s (1 init + 100 moves) and to avoid detection I would have to call the python interpreter from the os which would again cost a lot of time. It does not even matter what the time limit is just that it is not a vague 'don't be too slow' like it was initially, because I planned to simulate (100-1000 moves+init)*(number of programs I want to try), so if the number of programs I want to try is greater than 1 I would go over the limit if my opponent uses even just half the limit.

After this, seeing that I can't make my simulator work, I abandoned the idea of me submitting a simulator. However seeing that some other types of simulator can still be pretty strong, I decided to disincentivize them, so when Larian cautioned in the clique-chat that simulator crashing bots weaken our clique (as isusr restarts the whole tournament in the event of DQ), so we should not use them, I lied that I've already submitted one program detecting and crashing simulators. Of course Larian's point was valid, so obviously I did not even plan to do so. Some time later It occured to me that my claim that there is a simulator crashing bot in the clique might incentivize those who wanted to submit a simulator to leave the clique, so I added another lie that the method of detecting simulators was my friend's idea (hopefully suggesting that there is another contestant with the same method outside the clique). I'm curious how believable my lies were, I felt them to be pretty weak, hopefully it's only because of my inside view.

After this I had to come up with an actual program. My intrigue and life didn't leave me with much time, so I finally submitted a ZviBot (a bot similar to the one described in the Darwin Game series) as a payload (for those not in our clique: payload is the part of the CloneBot which activates in the endgame against other clique members). While I did not have time to run simulations, I had three reasons for this submission:

1. ZviBot has a good track record in a similar competition.
2. Given that bots in this competition know the round number, I expect that many will get meaner (less cooperating) in the later rounds on the grounds that if they survived for this many rounds they are probably a significant portion of the pool, so they can try to kill others. However because the programs will use different rates of becoming uncooperating, they will get eliminated from the pool one by one as the others are still cooperatating. By not getting meaner my plan was to stay in the final equilibrium state with others.
3. I was curious how such a simple bot would perform.

Bot detecting simulators:

class MatrixCrashingBot():
    def __init__(self, round=1):
       import inspect
       from time import sleep
       sf = inspect.stack()
       simulated = False
       enemy = ""
       for f in sf:
           if ('self' not in f.frame.f_locals):
               continue
           fo = f.frame.f_locals['self']
           fod = dict(inspect.getmembers(fo))
           if 'MatrixCrashingBot' != fo.__class__.__name__ and 'move' in fod:
               simulated = True
               enemy = fo.__class__.__name__
               break
       if simulated:
           while 1:
               print("{} tried to simulate me :O >:\[ So I sent him to an infinite cycle!\nNote to the tournament organizer: The infinite cycle is run by {} not by the MatrixCrashingBot! ".format(enemy, enemy))
               sleep(3)  
    def move(self, previous=None):
        return 3

Bot I finally submitted: (everything exept the payload is written by Vanilla_cabs. The core idea (alternating 3s and 2s) of the payload is from Zvi)

class CloneBot():
    def __init__(self, round=0):
        import math
        import random
        import extra
        self.math = math
        self.random = random
        self.extra = extra

        self.showdownRound = 90     # after this round, your personal program takes over
        self.round = round          # the current round
        self.myMoves = []           # all the moves you've made, first to last
        self.opponentMoves = []     # all the moves your opponent has made, first to last

        my_source_raw = extra.__getattribute__(''.join(['ge','t_','my','_s','ou','rce']))(self)
        opponent_source_raw = extra.__getattribute__(''.join(['ge','t_','op','po','ne','nt','_s','ou','rce']))(self)
        my_source = "\n".join(["    ".join(line.split('\t')).rstrip() for line in my_source_raw.splitlines()])
        opponent_source = "\n".join(["    ".join(line.split('\t')).rstrip() for line in opponent_source_raw.splitlines()])

        if not 'def payload(self) :' in opponent_source :
            self.is_opponent_clone = False
        else :
            my_common_code, my_payload = my_source.rsplit('def payload(self) :', 1)
            opponent_common_code, opponent_payload = opponent_source.rsplit('def payload(self) :', 1)
            if my_common_code != opponent_common_code :
                self.is_opponent_clone = False
            else :
                self.is_opponent_clone = True
                for line in opponent_payload.split("\n") :
                    # checks that no common method or property is overwritten after the payload
                    # allows the innocuous command "foo = 'bar'" by member's demand
                    if line.lstrip() != "" and line != "foo = 'bar'" and line[0:8] != "        " :
                        self.is_opponent_clone = False
                        break

            if self.is_opponent_clone :
                payload_length_difference = len(my_payload) - len(opponent_payload)
                if my_payload != opponent_payload :
                    # compares payloads without reading them
                    # fair way to decide who starts with 3 between two clones
                    # for 100% protection against ties, personalize your payload with a comment
                    self.high_first = (my_payload < opponent_payload) == ((payload_length_difference+round) % 2 == 1)
            
    def move(self, previous=None) :
        self.turn = len(self.myMoves)               # the current turn
        # pseudorandom to allow simulators to collaborate
        self.random.seed((self.round+1) * (self.turn+1) * (7 if previous==None else (previous+1)))
        
        if previous != None :
            self.opponentMoves.append(previous)
        if self.is_opponent_clone :
            if self.round < self.showdownRound :
                output = self.cooperateWithClone()
            else :
                output = self.payload()
        else :
            output = self.default()
        self.myMoves.append(output)
        return output

    def defaultCooperation(self) :              # factor influencing behaviour with non-clones, 1 at round 0, 0 at round 60
        return max(0.0, float(self.showdownRound - (self.round*1.5)) / self.showdownRound)
        
    def cooperateWithClone(self) :
        if self.turn == 0 :
            if self.high_first :
                return 3
            else :
                return 2
        else :
            return self.opponentMoves[-1]

    def default(self) :
        if self.turn == 0 :
            if self.random.random() < 0.5 * self.defaultCooperation() :
                return 2
            else :
                return 3
        elif self.myMoves[-1] + self.opponentMoves[-1] == 5 :
            if self.myMoves[-1] == 2 :
                return 3                        # tit for tat
            elif self.myMoves[-1] == 3 :
                if self.turn >= 2 :
                    if self.myMoves[-2] == 3 and self.opponentMoves[-2] == 2 :
                        return 3                # stable 3 against 2
                if self.random.random() < self.defaultCooperation() * 1.2 :
                    return 2                    # cooperation
                else :
                    return 3                    # maintain 3 against 2
            else :
                return self.myMoves[-1]         # free candy
        elif self.myMoves[-1] + self.opponentMoves[-1] < 5 :
            return 5 - self.opponentMoves[-1]
        else :                                  # sum > 5
            if self.random.random() < self.defaultCooperation() * max(0, 50-self.turn) / 100.0 :
                return 2                        # back down
            else :
                return 3                        # maintain
    
    def payload(self) :
        # put a personal word here to guarantee no tie during cooperation: in a pretty body no one can see your rotten soul
        # put what you want to play for the showdown
        # no line after 'def payload(self)' should have less than 8 whitespaces at the beginning,
        # unless it's an empty or only whitespace line
        #
        # Idea of solution: most program will gradually get meaner as rounds
        # progress, but because they do so at different rates
        # they will get eliminated as other, still cooperating bots outcompete their
        # meanness. By not getting meaner I plan to stay in the final equilibrium state.
        # Otherwise it's a ZviBot.
        if self.turn == 0:
            self.switched = False
            return 3
        else:
            # against very submissive bots
            if self.turn >= 3 and self.opponentMoves[-1] < 3 and self.opponentMoves[-2] < 3 and self.opponentMoves[-3] < 3:
                return 5-self.opponentMoves[-1]
            # against bots who are very bad at detecting patterns
            if self.turn >= 5 and self.opponentMoves[-1] == 3 and self.opponentMoves[-2] == 2 and self.opponentMoves[-3] == 3 and \
                    self.myMoves[-1] == 3 and self.myMoves[-2] == 2 and self.myMoves[-3] == 3 and not self.switched:
                self.switched = True
                return 3;
            if self.myMoves[-1] == 2:
                return 3
            elif self.myMoves[-1] == 3:
                return 2

class Foo():
    def __init__(self):
        self.x = 1

    def __init__(self):
        self.x = 2

Foo().x # 2

So, in case anyone's wondering what I did...

I cared enough to think and enter, but not to program. 

I designed a simulator, but was told it wouldn't be coded for me, so that was out.

So instead, I wrote this:

Until symmetry breaks, if the round # is 1, is 3 or is even, play sequence 23322232323322233 and then repeat 22222223 until symmetry breaks. If round # is odd and 5 or more, the reverse, except repeating 22222223 at the end.

Once it breaks, alternate 2 and 3 for 4 turns.

Then, if the last turn added to 5, keep doing that until they don't.

Once they don't...

If they've always played 0 or less, play 5.  

If they've always played 1 or less, play 4.  

If they've always played 2 or less, play 3.

Otherwise, depending on round number:

Rounds 1-50: Keep alternating until turn t+10. After that, if last turn added to 5, alternate 2 and 3. Otherwise, check their average score per round after symmetry. If it's 2.5 or lower, play 2, otherwise play 3. 

Rounds 51-100: Same as above, except you also always play 3 if their score is 5 or more higher than yours.

Rounds 101+: Same as above, except you also always play 3 if their score is higher than yours.

(We could improve by adding more logic to properly exploit in strange situations, but we don't care enough so we won't.)

That's it. Keep it simple. Still call it BendBot I guess.

The intention here was pretty basic. Endgame behavior varies by round to get stingier if anyone tries something, to grab early pool share without being exploited later.

The big thing is that this bot is deterministic. I intentionally avoid calling the random function by choosing a semi-random set of 2s and 3s, on the theory that it's unlikely anyone else would choose an identical sequence, and if I meet myself I get the 2.5 anyway.

If they are not simulating or checking code, it won't matter.

If they are looking at all, then my not loading their code and not being random tells them the water's fine, take a look, see what's going on, and we can cooperate fully - you can see what I'm starting with, and we can get 2.5 each without incident. I'm sad that some people thought that more than two parenthesis was high risk to simulate/examine - I thought that the obvious thing to do was check to see if someone ever loads code or uses a random function, and if you don't do either, you should be safe.

So the thought was, many of the best bots would be simulator bots and I'd get full cooperation from them, whereas when they faced each other, they'd have to do some random matching to cooperate, so I'd have an edge there, and I'd do reasonably well against anything else that went late unless some alliance was afoot.

Turns out an alliance is afoot after all, but I certainly didn't care enough to worry about that. Let them come, and let the backstabbers profit, I say.

I was told that I had by far the most complicated non-coded entry even then, and that my endgame logic was being replaced with randomly 50% 2, 50% 3. I was asked, submit as-is, fix it, or withdraw?

That modification definitely didn't work, and the code that was written was not something I felt OK touching. So I explained why, and suggested it be replaced with this:

If (last round added to 5 or less) play whatever they played last.

Else If (their score > my score and round > 5) play 3.

Else Play 2.

I figured that was one extra line of code and should take like 2 minutes tops, and if that was 'too complex' then that was fine, I'd sit out.

So basically, let myself get exploited very early since there would likely be at least one all-3s in the mix but all such things would swiftly lose, then shift to hardcore mode a little faster to keep it simple.  

I didn't get a reply to that, so I don't know if my entry is in or not. I hope it is, but either way, good luck everyone.

(import random)
(setv +sequence-1+ [2 3 3 2 2 2 3 2 3 2 3 3 2 2 2 3 3])
(setv +sequence-2+ [2 2 2 2 2 2 2 3])

(defclass BendBot []
  (defn --init-- [self &optional [round 0]]
    (setv self.round round)
    (setv self.opponent-record [])
    (setv self.record [])
    (setv self.turn -1)
    (setv self.count-to-four 0)
    (setv self.terminal-behavior False))

  (defn move [self &optional [previous None]]
    (+= self.turn 1)
    (if previous
        (.append self.opponent-record previous))
    (setv output
          (if (= self.opponent-record self.record)
              (if (or (% self.round 2)
                      (< self.round 4))
                  (if (< self.turn (len +sequence-1+))
                      (. +sequence-1+ [self.turn])
                      (. +sequence-2+ [(% (- (len +sequence-1+)
                                             self.turn)
                                          (len +sequence-2+))]))
                  (if (< self.turn (len +sequence-1+))
                      (. (list (reversed +sequence-1+)) [self.turn])
                      (. +sequence-2+ [(% (- (len +sequence-1+)
                                             self.turn)
                                          (len +sequence-2+))])))
              (if (< count-to-four 4)
                  (do
                    (+= count-to-four 1)
                    (if (= (last self.record) 3)
                        2
                        3))
                  (if (or self.terminal-behavior
                          (= 5 (+ (last self.record) previous)))
                      (if (= (last self.record) 3)
                          2
                          3)
                      (do
                        (setv self.terminal-behavior True)
                        (if (all (map (fn [x] (<= x 0)) self.opponent-record))
                            5
                            (all (map (fn [x] (<= x 1)) self.opponent-record))
                            4
                            (all (map (fn [x] (<= x 2)) self.opponent-record))
                            3
                            (if (> (+ (last self.record)
                                      previous)
                                   5)
                                3
                                2)
                            ))))))
    (.append self.record output)
    output))

The first line says "Entries must be submitted on October 18, 2020, or earlier."

Then a bit later you say "I will run my own version of the game on October 16, 2020."

Will you be making your time-travel technology available to contestants' bots, and if so what is the API they should use?

Your TitForTatBot
* never sets self.previous
* even if it was set, it would stop cooperating when opponent played 0

Also I agree with Zvi's comment, why 2.5 for free? This way one should really concentrate on maxing out in the early stage, is it intended?

Will post a link to a github repo with my code later today (when I'm not meant to be working), but for now, here's my thought processes.

(Edit: my code is here. My entry is in incomprehensibot.)

class CloneBot():
    ...
    def payload(self) :
        ...

    foo = 'bar' # allowed

foo = 'bar' # forbidden

What timezome is the deadline in? Or to be maximally precise – can you give a final submission-hour in UTC?

Great initiative, thanks for organizing!

Fun!  Note that the "automatic recognition of self" and "group, not individual fitness" rules are different from many such contests.  I think it's likely that this allows super-simple bots to win, if the initial mix allows them to get past the first few iterations.  

I'd predict three-bot is the most likely simple winner - it gets full value against itself (as does everyone), and gets some points for all opponents' probes and complex signaling (that includes bidding 0, 1, or 2).  It NEVER gives an opponent more points than it gets.  

When you add in truly sophisticated bots, who exploit each other based on knowledge of the mix of opponents, they can do enough better in early rounds for three-bot to never get critical mass.  Likewise for coordinated bots who can accurately detect each other, getting full value for more cases than non-coordinated ones.

edit: after reading Zvi's old posts, I realize two things: 

1. auto-self-recognition (but not auto-partner recognition) is weird, and probably changes the correct explore-exploit strategy significantly.  Perhaps not as far toward the simple as I propose, above - partner recognition is going to be important.
2. starting mix matters a whole lot.  it'll be a very different game with 100,000 initial programs than with 50.  And there will be a groupthink component - there's no way to avoid the meta-game of un-enforced partnerships.

A thought for next time, if you want to build a simulator, it could make sense to wait one round before simulating anything even slightly unsafe, and do something simpler in round 1. That way, if something weird might potentially disqualify you but will itself get disqualified, it dies before it can remove you from the pool. 

I don't know whether it's a competitive entry (it would be a FoldBot in Zvi's taxonomy [LW · GW]), but as a quick piece of software, I'm pretty proud of AbstractSpyTreeBot!

To check, what timezone is the deadline in?

This is the Nash bargaining game. Is there some specific reason to call it a "Prisoner's Dilemma variation", or is it just "everyone has heard of the Prisoner's Dilemma, and don't have a generic term for this kind of game-theory tournament"?

I'm a non programmer, if I submitted a bot that's too complicated or that is supposed to do something that isn't a possible move, would I be contacted and get a chance to change it, provided I submit it early enough?

Could you provide one or more examples of too complicated descriptions, just so I know for which level of complexity I should aim? I'm not clear on how you would consider a bot that has a decision three with different options and processes but no part that's hard to program, for example. (To avoid giving hints or good ideas, they can be filled with completely stupid instructions or be for bots that try to do some other stuff)

What are the rules about program runtime?

If you face a copy of yourself you are automatically awarded the maximum 5 points per round

What's your rationale behind this? Isn't part of the point that you need to be able to survive even in an ecosystem consisting mainly of you?

Are comments allowed?

# Comments are allowed in the code.

Is the number of rounds per matchup going to be in the tens, or the thousands?

Edit: I just realised you specified in the post

.