[alphaalpha101]

So this new concurrent map? Am I right in understanding it's designed for cases where you have a map shared between goroutines but where each goroutine essentially owns some subset of the keys in the map?

So basically it's designed for cases like 'I have N goroutines and each one owns 1/N keys'?

[vanderZwan]

> each goroutine essentially owns some subset of the keys in the map

With those constraints, why not create a small map for each goroutine at that point, and merge the maps afterwards?

[imaginenore]

Then you have to merge them on every read (after any modification).

[squiguy7]

This lightning talk gives some great information on use cases for the new sync.Map: https://youtu.be/C1EtfDnsdDs

[deckarep]

Wow great find!

[artursapek]

It could just be one map shared by many goroutines, which normally causes a panic:

    fatal error: concurrent map writes

[freecodyx]

i am dealing with this problem right now. also i have a big problem with deepclone,

I did a big rewrite of a current project, and clearly it was badly designed :(

[azinman2]

Standard practice is to use a mutex to guard against concurrent usage.

[logicallee]

also necessary for reads?

Also, do you have any good references to proper best practices around concurrent and parallel programming? (in Go.) Like just basic things. Code I can copy and paste without it having obscure race conditions because that use of mutex is absolutely correct, and something that lets me understand the limitations. I feel like it is very easy to do things "wrong" or not notice some edge cases. In C++ I didn't only ever coded single-threaded for this reason. Too many gotchas. Any help would be appreciated.

[dgellow]

I would suggest you to read the book "Concurrency in Go", by Katherine Cox-Budai, 2017: http://shop.oreilly.com/product/0636920046189.do

[logicallee]

Thank you for the recommendation!

[carbocation]

Necessary for reads unless no additional writing will be done. If you initialize/write into a map and then later have concurrent reads from it, the program will run. If you try to write in the midst of this, it will crash.

[alphaalpha101]

I really, really don't understand why this would get downvoted. Are people not allowed to ask questions now?

[pvg]

They're discouraged from complaining about downvoting.

[alphaalpha101]

It was not a complaint, it was a question, just like my top-level comment.

Was that interpreted as a complaint as well? Is that the problem?

[pvg]

It sounded like complaining but either way, take a look at these.

https://news.ycombinator.com/newsguidelines.html

"Please don't comment about the voting on comments. It never does any good, and it makes boring reading."

[issaria]

A concurrent map in my understanding, is a map that can be accessed concurrently without explicit synchronization, not each coroutine has a piece of it. Check java ConcurrentHashMap.

[kraig]

or you just have two or more goroutines that need to modify a map