Input/Output multiple values from function

Jabari Zakiya jzakiya at
Thu Aug 29 10:39:44 UTC 2019

On Thursday, 29 August 2019 at 09:04:17 UTC, Simen Kjærås wrote:
> On Wednesday, 28 August 2019 at 13:11:46 UTC, Jabari Zakiya 
> wrote:
>> [...]
> Reduced example:
> unittest {
>     int[] a;
>     // cannot implicitly convert expression a of type int[] to 
> shared(int[])
>     shared int[] b = a;
> }
> This is because an int[] is mutable and thread-local, while 
> shared(int[]) is mutable and shared. Shared mutable data must 
> be guarded closely, preferably behind a mutex or similar. 
> Assigning the value of `a` to `b` above would leave a mutable 
> reference to the shared data on a thread, and could easily lead 
> to race conditions.
> In order to fix this issue, consider several things:
> Do modpg and friends really need to be shared? Removing 
> shared() from them will still make them available to other 
> parts of your code, but they will be thread-local instead. If 
> you're not doing threaded work, that should be perfectly fine.
> Can they be immutable? If they're initialized once and never 
> changed, this could be a good solution.
> If they need to be shared and mutable, have you protected them 
> enough from race conditions? Are there possible situations 
> where other threads may be accessing them while one thread is 
> writing to them?
> Multi-threaded programming is hard, and requires a lot more 
> knowledge than we have about your project from the code you've 
> posted, so only you can answer these questions. If you're 
> unsure, you can probably just remove shared() from modpg and 
> friends.
> --
>   Simen

The values modpg, res_0, restwins, and resinvrs are constant 
(immutable) values that are generated at run time. They are 
global/shared and used inside threads.

So this process is initializing them at the start of the program, 
based on the input values to it.

The compiler only has a problem, it seems, with the arrays and 
not the single values.

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