Progress printing with threads?

[Stanislav Blinov]

On Wednesday, 1 July 2020 at 07:52:28 UTC, AB wrote:
> Hello. I am unsure how to proceed about printing progress in my 
> program.
> Is it a good idea to std.concurrency.spawn a new thread?..
> This example code shows my situation:
>
>     MmFile  input       = new MmFile(/* ... */);
>     ulong   fileSize    = input.length;
>
>     for (ulong i = 0; i < fileSize; ++i)
>     {
>         // ...
>     }

If you can only update the progress between iterations I don't 
see why you would use threads here. A timer should suffice:

import std.datetime.stopwatch;

MmFile  input       = new MmFile(/* ... */);
ulong   fileSize    = input.length;
auto    sw          = StopWatch(AutoStart.yes);

for (ulong i = 0; i < fileSize; ++i)
{
       // ...
       if (sw.peek >= 2.seconds)
       {
           writefln("Progress: %5.2f%%", i*100.0/fileSize);
           sw.reset;
       }
}