Update: The current settings of 1.9 should run at least as fast as the previous Kotlin 1.6.

Dear codeforces and MikeMirzayanov,

Please restore Kotlin 1.6.

This issue could be serious enough to end my CP career.

The short story is that Kotlin 1.6 is the only 32-bit version. Without Kotlin 1.6 we must submit in 64bits, and in many situations this will be too slow.

As the only 32 bits version available of the language, it should not have been removed to begin with.

After using the exact language version on Round 920 (Div.3) having decent success, I found that I was unable to submit in Kotlin 1.6: It seems that Kotlin version 1.6 had been removed.

If this is a mistake, please restore it. If this is simply the result of having three languages versions being too much: You could probably remove 1.7.20, as 1.9.21 seems to be superior in every way.

The version 1.6, — more precisely, the 32 bits environment and the associated JVM settings/ versions etc.. Are critical to viability to use Kotlin on codeforces. I still find 1.6 to be consistently the fastest version, and will only use 1.7/1.9 on specific situations (e.g. during 64 bits operations). On solutions that heavily uses boxed integers i.e. MutableList (which is necessary for the most convenient solutions), Kotlin 1.6 runs two or three times faster. Even without those, the solution could still be anywhere from 20% to 50% slower.

This has been pointed out in a comment I wrote earlier, link. It had always been a serious fear of mine that codeforces would just drop Kotlin 1.6 randomly. I hope that codeforces can recognise how much differences this little bits of speed make: With 1.6, even if solutions that got TL can probably pass under a small optimisations. If 1.6 is not available, I can imagine situations where it is seriously difficult to pass an intended solution (especially when the TL was not made lenient for one reason or another), at least, without having multiple TLE penalties. An example that comes to my mind is 241859779 : my contest submission is 600ms, submission in 1.9 is 950ms, awfully close to TL.

I don't believe Kotlin 1.6 and 1.9 have the same speed: For a simple example, the solutions I submitted in the div3 round toady:

For most submissions they run in ~200ms, so the speed difference probably won't matter much as it is a constant initiation time. For the two problems that run more than that:

Problem F: 1.6, 1000ms 241743081, 1.9 , 1400ms 241859276 Problem G: 1.6, 400ms 241772417, 1.9 , 700ms 241859263

In conclusion, please restore Kotlin 1.6.