On Monday, 29 February 2016 at 12:43:39 UTC, Chris wrote:
What's the best way to make an assoc array fit for
multi-threading? If this is not possible what would be the best
alternative?
Say, for example, `data` is used by a class that is globally
accessible to all threads. E.g. like this:
string[string] data; // defined somewhere
public string getData(string key)
{
if (key in data)
return data[key];
else
return "";
}
I'm almost sure that built-in AAs don't provide automatic
synchronization (in my tests I hit a deadlock), but you can
easily wrap the AA into a struct that does the necessary
synchronization. However be aware that even then you are not
going to be safe, because more than one thread can try to access
the keys or the values of the AA. Also note that because the
built-in AAs rely on the GC, you may get poor scaling because
every memory allocation can potentially take the global GC lock,
which will block all threads from doing any work. So do your own
tests and if you find the need to improve the performance, I
would suggest investigating replacing the built-in AA with (for
example) the hashmap from
https://github.com/economicmodeling/containers in combination
with a thread-local allocator.
Here's an example of how to wrap an AA into a moderately safe
accessor. In the following example I create an additional thread
which concurrently adds odd numbers into the AA, while the main
threads add even nubmers:
http://dpaste.dzfl.pl/06025e6374eb
It segfaults on DPaste because you can't create threads there,
however it works ok on my machine. The output look like this:
"0" : 0.140450140112896
"1" : 1.140450129700608
"2" : 2.140450140112896
"3" : 3.140450129700608
"4" : 4.140450140112896
"5" : 5.140450129700608
"6" : 6.140450140112896
"7" : 7.140450129700608
...
