# 1.0 multi-threading memory use issues **URL:** \ **Category:** Crystal Contrib\ **Created:** [August 18, 2020, 6:22pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454 "2020-08-18T18:22:32Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![jzakiya](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/jzakiya/32/278_2.png) [@jzakiya](https://forum.crystal-lang.org/u/jzakiya)\ **Post date:** [August 22, 2020, 6:41pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/21 "2020-08-22T18:41:16Z")
Hey @asterite, after studying your code, I just replaced the `Arrays` with `Slices` in the two methods `twins_sieve` and `nextp_init` in my original version, as you did in your code, and here are the results, for input of 1\_000\_000\_000\_000. My original using Arrays: 174.5 secs My original using Slices: 161.1 secs The memory still grows as before, but that’s seem to be due to, as your stated, the incomplete multi-threading model. I want to say I really appreciate how you jumped on this issue and made the code much better. I have no doubt Crystal will catch up to Nim, Rust, et al, in multi-processing very soon. Please feel free to use this application as you please as a test case. Here is the updated gist of my code using `Slices`. > ---
**Author:** ![asterite](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/asterite/32/60_2.png) [@asterite](https://forum.crystal-lang.org/u/asterite)\ **Post date:** [August 22, 2020, 9:53pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/22 "2020-08-22T21:53:44Z")
Cool! Yeah, I love optimizing things. It strange that the memory keeps goigg up for you. In my case it never goes beyond 20MB. Maybe a difference of OS? No idea. ---
**Author:** ![scott](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/scott/32/948_2.png) [@scott](https://forum.crystal-lang.org/u/scott)\ **Post date:** [August 22, 2020, 10:54pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/23 "2020-08-22T22:54:49Z")
> [@asterite](#): > > And no, there will never be manual memory management in Crystal. There already is, one can call `LibC.malloc` as easily as any other C function. ---
**Author:** ![jzakiya](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/jzakiya/32/278_2.png) [@jzakiya](https://forum.crystal-lang.org/u/jzakiya)\ **Post date:** [August 22, 2020, 11:01pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/24 "2020-08-22T23:01:24Z")
> [@asterite](#): > > It strange that the memory keeps goigg up for you. In my case it never goes beyond 20MB. Maybe a difference of OS? No idea My laptop for these results is a 2011 Lenovo, I5 2C|4T, 2.9 GHz, Linux kernel 5.7.15. Crystal 0.35.1 ---
**Author:** ![ComputerMage](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/computermage/32/719_2.png) [@ComputerMage](https://forum.crystal-lang.org/u/ComputerMage)\ **Post date:** [August 24, 2020, 8:20pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/25 "2020-08-24T20:20:52Z")
Actually, I want to experiment with that flag as part of my old idea to use ARC (automatic Reference Counting) as possible option to GC. ---
**Author:** ![giuse](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/giuse/32/600_2.png) [@giuse](https://forum.crystal-lang.org/u/giuse)\ **Post date:** [August 25, 2020, 12:58pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/26 "2020-08-25T12:58:56Z")
And how do you use in crystal? I’ve got no idea and I thought it would be impossible due to the strong type system ---
**Author:** ![scott](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/scott/32/948_2.png) [@scott](https://forum.crystal-lang.org/u/scott)\ **Post date:** [August 26, 2020, 5:34pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/27 "2020-08-26T17:34:55Z")
Yes, to be absolutely clear, doing so is **inherently unsafe** and can _easily_ lead to memory leaks! `LibC.malloc` returns a raw [`Pointer`](https://crystal-lang.org/api/0.35.1/Pointer.html), which you can then wrap in a slice and pass around like any other, but doing so discards guarantees the compiler offers (memory safety). ---
**Author:** ![ComputerMage](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/computermage/32/719_2.png) [@ComputerMage](https://forum.crystal-lang.org/u/ComputerMage)\ **Post date:** [August 27, 2020, 9:51pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/28 "2020-08-27T21:51:12Z")
That’s where ARC should help. ---
**Author:** ![scott](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/scott/32/948_2.png) [@scott](https://forum.crystal-lang.org/u/scott)\ **Post date:** [August 27, 2020, 10:03pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/29 "2020-08-27T22:03:12Z")
ARC would be a dream come true, for sure! I just don’t feel capable of implementing it personally. ---
**Author:** ![ComputerMage](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/computermage/32/719_2.png) [@ComputerMage](https://forum.crystal-lang.org/u/ComputerMage)\ **Post date:** [August 27, 2020, 11:31pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/30 "2020-08-27T23:31:48Z")
I am planning to do it but don’t have enough time. It may be equal or even may be more work than debugger support (I spent 6 months on it). But I am still willing to work on it as it is an interesting idea to implement. ---
**Author:** ![megatux](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/megatux/32/164_2.png) [@megatux](https://forum.crystal-lang.org/u/megatux)\ **Post date:** [August 28, 2020, 4:46pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/31 "2020-08-28T16:46:51Z")
You mean ARC like the ones implemented in Swift & ObjectiveC with the LLVM support? ( **retain** and **release** ). That would be awesome, I think. ---
**Author:** ![jzakiya](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/jzakiya/32/278_2.png) [@jzakiya](https://forum.crystal-lang.org/u/jzakiya)\ **Post date:** [August 28, 2020, 6:46pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/32 "2020-08-28T18:46:40Z")
You may want to follow the development of Nim’s ARC. [https://forum.nim-lang.org/t/5734](https://forum.nim-lang.org/t/5734) > **[NimConf 2020](https://conf.nim-lang.org/)** > > NimConf 2020 will take place on June 20th at 11am UTC. Streamed live and for free from YouTube. ---
**Author:** ![ComputerMage](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/computermage/32/719_2.png) [@ComputerMage](https://forum.crystal-lang.org/u/ComputerMage)\ **Post date:** [August 29, 2020, 10:37pm UTC](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454/33 "2020-08-29T22:37:13Z")
Yes, exactly that approach. [Previous page](https://forum.crystal-lang.org/t/1-0-multi-threading-memory-use-issues/2454.md?page=1)