Great. Thanks! Looks like it's just better if I return a struct if these goroutines are operating independently anyway.
On Monday, March 13, 2017 at 12:20:42 AM UTC-7, Konstantin Khomoutov wrote: > > On Sun, 12 Mar 2017 23:39:59 -0700 (PDT) > Albert Tedja <nicho...@gmail.com <javascript:>> wrote: > > > I know map itself isn't threadsafe, but I am just wondering how > > threadsafe it is if you can be absolutely sure that each goroutine > > accesses a different key in the map. > > Say, goroutine 1 accesses mymap["1"] > > and goroutine 2 accesses mymap["2"] and so on. > > Contrary to a struct type, values of which are just pretty "static" > pieces of memory, where the compiler known an offset (in bytes) of each > field relative to the value's starting address, a value of a map type > contains a pointer to an intricate *dynamic* thing, where each insertion > of a new value might lead to drastic changes like moving of unrelated > values already stored in that map in memory. > > Because of this, the only thing guaranteed to work concurrently with Go > maps is reading them. So if your goroutites only read a map value, > then it does not matter which values they read. If they write to a map > (that is, insert into it or delete from it), you must synchronize the > accesses to that no write even happens concurrently with either another > write or a read. > > On the other hand, consider that if you store in the map pointers to > actual values which are themselves not stored in a map, then, after > reading such a pointer from a map, you're free to deal with the value > it points to concurrently with map modification. That's because in > this scenario, the only values stored by the map are pointers, and > hence insertion to the map and deletions from it might move those > pointers in memory but not the values they point to. > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
