"The EX raid compendium: everything we've learned about EX raids (trigger conditions, scheduling algorithm, timing calculation, and more!)"

#PokemonGO: Hi folks,This post will attempt to cover everything we know about EX raids. It is both a reference for players to learn about EX raids, and also a summary of the findings from some EX raid experiments I have conducted and historical data I have collected.Firstly, some stats on the data:I have collected EX raid records for my area for over 500 EX raids since October 2017.I have good (not perfect) visibility of raids conducted in my area thanks to a large active discord community and Messenger raid groups.For the past 10 weeks, I and a dedicated group of local raiders have targeted low-activity EX-eligible gyms and logged all raids conducted there, in an effort to learn more about EX raids.Without further ado, lets start with the basics.What is an EX raid?An EX raid is a special invite-only raid battle with a powerful raid boss. Historically (and currently), the boss has been Mewtwo. EX raids can only occur at specific gyms, and under certain conditions, which are detailed below. Once you receive an EX pass, you can attend the gym at the specified time for a chance to defeat and capture the EX raid boss. More information about battling Mewtwo can be found here: https://ift.tt/2zJDjeB makes a gym EX eligible?The only types of gyms that are eligible for EX raids are sponsored gyms and gyms in parks. The former is rather easy to check, but the latter is a bit more complicated. Niantic loosely consider 'parks' as areas in OpenStreetMap (OSM) tagged with labels such as leisure=park and landuse=recreation_ground. A comprehensive guide to checking which gyms are EX eligible can be found here: https://ift.tt/2uo2v5l important to note that newly-created gyms that satisfy these criteria will be eligible too. So whilst Niantic haven't updated the OSM data since ~July 2016, it is possible to get new EX eligible gyms in your area.There is also some speculation that areas with tags like highway=pedestrian and amenity=fountain can block a gym from being EX eligible, despite it being a sponsored or park gym. There is only 1 gym that this applies to in my area, and it hasn't had any EX raids despite being in a very high traffic area, so I subscribe to this theory. You can find more info about blocking tags here: https://ift.tt/2zJ0HJn are passes handed out?EX raid passes are normally handed out once per week in a big wave, at roughly the same time for everywhere in the world. Once passes are issued, the selected gyms become raid-locked, and will not host any other raids until the EX raid has occurred.The date that passes are issued on and for change on a step schedule, such that each day has a few EX raids before moving to the next day (a day being Monday, Tuesday, etc.). I can't find a pattern for this schedule that has always proven correct, but there are 2-3 weeks of each day before going to the next day. For example Mon, Mon, Tue, Tue, Tue, Wed, Wed, Wed, Thu, etc. If you have a compelling theory for the actual pattern, I would be happy to update and add it here.One important observation from this process is that when passes are issued for a new day, the next pass handout will generally happen 1 day later. For example, lets say you've had a few weeks of passes being handed out Monday for Tuesday EX raids. Once you get a handout for a Wednesday EX raid, the next handout will be on the following Tuesday.What is required to trigger an EX raid at an eligible gym?Ok, on to the juicy stuff. In Feb 2018, Niantic adjusted the EX raid system so that "the number of Gyms that meet the necessary criteria for an EX Raid Battle will increased". There were some teething issues with the changes, but as of the wave of passes released on 16/3 for EX raids on 24/3, these changes started having a profound effect on the EX raid ecosystem in my area - we went from getting ~10 EX raids per wave to ~20.I believe the current "trigger requirement" is simply somewhere between 20-25 unique accounts raiding the gym in the last 7 days (or since last EX raid, if that is sooner). The types of raid do not matter. The lobby sizes do not matter. Accounts raiding multiple times do not matter.The lowest number of known accounts (trigger group + additional players met at the EX raid itself) that we have triggered an EX raid with is 23. Of course, there is always the possibility of other unaccounted raiders who also couldn't make the EX raid, or spoofers. But our group intentionally target quiet or previously un-triggered gyms to try to minimise the chance of these variables, and most times we account for 100% of the players that show up for the EX raid (again, discounting potential spoofers). I personally believe the required number may be 20, since that is the recommended group size for battling Mewtwo. If you have examples of 20+ accounts raiding an eligible gym and not triggering an EX raid, I invite you to read the rest of this post before commenting, as I hope it will explain why.As for the eligibility window, I am quite sure it is 7 days. We have several examples of someone raiding a gym 7 days + ~8 hours prior to passes going out, and them not receiving a pass. This can happen if raids are done shortly after EX passes going out for a new day in the schedule, since that means the following passes will be issued in 8 days time. If you want to be safe, don't bother raiding EX eligible gyms on the day of other EX raids.How does the pass distribution system work?Ok travellers, here is what I personally believe to be the most useful and new information in this post; a fully structured pseudo-code implementation of the EX pass distribution algorithm. I will highlight that this is speculation based on observed data, not the actual algorithm retrieved from the server or something. Here goes:// grab a list of all the gyms that 'triggered'Select GYMS where EX_ELIGIBLE is True and NUM(ELIGIBLE_RAIDERS) > 20// sort by least to most raidersSort GYMS by NUM(ELIGIBLE_RAIDERS)// progress through the list of gyms, handing out passes, but only if there's still enough recipientsFor each GYM, if NUM(ELIGIBLE_RAIDERS) > 20: issue passes to ELIGIBLE_RAIDERS remove ELIGIBLE_RAIDERSThat's it! Simple, isn't it? What I am proposing here is that the algorithm generates passes for the least-popular triggered gym first. Then it removes the pass recipients from the eligible raiders list. As it goes through, if it gets to a gym that no longer has enough eligible raiders, no passes are issued.As far as how this affects you individually, you'll notice there is no selection based on badge level or overall raiding activity. 100% of eligible raiders get a pass. If you raid an EX eligible gym and it gets an EX raid, you get a pass (unless you already got a pass for a less-popular gym). You can use this to guesstimate the popularity of the gym too. For example, lets say you and a friend raid gym A, and you raid gym B by yourself. Both gyms hand out passes for EX raids, but your friend gets gym A and you get gym B. This means gym B had less eligible recipients, and so had higher priority to give out passes.One thing I will point out is that I don't know where and how the 1-per-level-13-cell selection is done, as I have no data for 2 eligible gyms in the same level 13 cell both being unlocked at the same time. The list of Gyms might be reduced to 1-per-level-13-cell before sorting, or the pass handout loop might also include a condition that no other gym in this gym's level-13-cell has had passes issued yet.What can cause an EX raid trigger to fail?In my opinion, the above algorithm would explain why some extremely popular gyms, e.g. in CBD areas, do not regularly receive EX raids. They have too many eligible raiders, and so are quite far down the list for pass handouts. Too many of the eligible raiders receive passes for other gyms, so when it comes time to hand out passes for the popular gym, there aren't enough eligible accounts left, so it gets skipped. We attempted to exercise this condition by triggering two different gyms with mostly the same group, e.g. 35 accounts at one gym, then 25 of those at a different gym. However, we were unlucky with the raids at those gyms, so we failed to achieve this split.  There is also a theory commonly refereed to as "clock-blocking", whereby an active raid at a gym during pass handout will prevent passes being issued for that gym. I have zero experience with this, since passes are issued in the early morning here, before any raids are active. I believe this thread is the most compelling evidence of clock blocking, but I can offer no further insight: https://ift.tt/2uo2xtZ is the EX raid time calculated?This is another very interesting topic, and I have posted about it several times before. Since the March 24th EX wave, 212/412 EX raids (~51%) in my area have been at 1PM. For our trigger group, we have had EX raids at 6PM, 1PM, 1PM, 1PM, 1PM, 1PM, 6PM, 5PM and 1PM. As far as I can tell, there is no discernible difference between our activity when we receive raids at 1PM vs. 5-6PM. Therefore I am left with the following theory: 50\% of the time the EX raid time will be the 'popular time', and 50\% of the time it will be 1PM.If you assume this 50% chance of 1PM, then our trigger group's other raid times could equally be explained by average time, OR the first eligible raid of the cycle. We will continue to investigate this, but while there is a significant chance that our hard work will just be tossed aside in favour of a 1PM raid, it is very frustrating to test. You can read more about my average time calculation here: https://ift.tt/2LmIzGk some data supporting 'first eligible raid' here: https://ift.tt/2uo2y11 an EX raid be cancelled?Yes, a scheduled EX raid can be cancelled if the gym gets deleted or moved. It may also happen if it is a sponsored gym and the sponsorship deal expires. You get some premium passes and stardust as compensation.Future workThere is still much work to do travellers! If you are interesting in contributing to the EX raid collective knowledge, here are some experiments I would love to see carried out:More testing of first raid time vs. average raid time for non-1PM EX raidsFine-tuning of the number of unique accounts to triggerTesting of the lower bound for triggered gym to *not* produce passes. Is it the same as the former, or is it lower?Testing of multiple gyms in the same level-13 cell. Which one gets selected? The more popular, or the lesser?What happens if you raid a popular gym multiple times, and a less-popular gym only once? Do you still get a pass for the less popular gym? (I have anecdotal evidence to suggest you still get the less popular gym)That's all I have for you today. If you think I have omitted an important detail about EX raids, please let me know and I will update the post. I welcome any and all discussion, dissenting or otherwise! via /r/TheSilphRoad https://ift.tt/2LmF56M