If we take into account 1 million players, and assume that each of them is having 20 blueprints in their library and all of the blueprints are random, the chance that it happens at least once is 9%. The CRC is 32 bit, so there are 2^32 combinations. We were also wondering how big is the chance, that 2 blueprints in one blueprint library will have the same CRC. Anyway, forcing the serialiser to not write the map version to the output in this case fixed this issue. It was quite hard to reproduce because of this. This means, that whenever we changed version of factorio, which is every release at least, the CRC values of the blueprints changed, and they were suddenly considered to be different. The problem is, that our MapSerialiser writes current output map version automatically in a constructor. The way it works is, that the blueprint is saved as it would be normally saved, but instead the data goes into a CRC engine. After some digging, we discovered what is wrong:ĬrcWriteStream* crcWriter = new CrcWriteStream() That some property of an entity in the blueprint isn't initialized properly, so the CRC would be different for 2 blueprints that are the same. We assumed, that the error is in the CRC generation from the blueprint entities. For some reason, this wasn't working perfectly, as a lot of players were reporting that blueprints are somewhat being duplicated in the library. This can be used to quickly detect a duplicate blueprint when merging player blueprint libraries and blueprints stored in a save.

For performance reasons, the blueprint library generates and stores CRC of each blueprint. We had trouble with the blueprint library, mainly the blueprint duplication problems. Sadly, this will change our attention to just different category of bugs: Those that we plan to fix for the 0.16 as they are not so critical and the changes required to fix them are too big to be done in 0.15 at this point. The (wishful) plan is to have a stable candidate for 0.15 next week. After weeks and weeks of going through bug reports and fixing stuff (after all 0.15 was one of our biggest releases), it seems that we are approaching the end of 0.15 stabilisation.

Factorio rail signal tutorial