• AB (21/21) Jul 01 2020 Hello. I am unsure how to proceed about printing progress in my
• Stanislav Blinov (16/26) Jul 01 2020 If you can only update the progress between iterations I don't
• Simen =?UTF-8?B?S2rDpnLDpXM=?= (24/45) Jul 01 2020 If doing the update in the same thread that does the processing

AB <ab396356 users.sourceforge.net> writes:

Hello. I am unsure how to proceed about printing progress in my 
program.

Suppose the program is processing a very big file and is 
iterating the file's bytes using a for loop. The processing takes 
several minutes and I want a progress percentage be printed every 
2 seconds in this manner:

Progress: 0.40%
Progress: 3.20%
Progress: 5.73%

Is it a good idea to std.concurrency.spawn a new thread and pass 
to it
     cast(float)i * 100 / fileSize
somehow? If not, what's a better way to do this?

This example code shows my situation:

     MmFile  input       = new MmFile(/* ... */);
     ulong   fileSize    = input.length;

     for (ulong i = 0; i < fileSize; ++i)
     {
         // ...
     }

Thanks in advance.

Stanislav Blinov <stanislav.blinov gmail.com> writes:

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;
       }
}

Simen =?UTF-8?B?S2rDpnLDpXM=?= <simen.kjaras gmail.com> writes:

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.

 Suppose the program is processing a very big file and is 
 iterating the file's bytes using a for loop. The processing 
 takes several minutes and I want a progress percentage be 
 printed every 2 seconds in this manner:

 Progress: 0.40%
 Progress: 3.20%
 Progress: 5.73%

 Is it a good idea to std.concurrency.spawn a new thread and 
 pass to it
     cast(float)i * 100 / fileSize
 somehow? If not, what's a better way to do this?

 This example code shows my situation:

     MmFile  input       = new MmFile(/* ... */);
     ulong   fileSize    = input.length;

     for (ulong i = 0; i < fileSize; ++i)
     {
         // ...
     }

 Thanks in advance.

If doing the update in the same thread that does the processing 
is somehow not an option, this works for me:

import std.concurrency;
import std.stdio;
import core.thread;
import core.time;

void main() {
     ulong filesize = 1234;
     ulong i = 0;
     Tid progress = spawn((shared const(ulong)* p, ulong f){
             while (!receiveTimeout(2000.msecs, (int i){ })) {
                 writeln(*p, "/", f, ": ", *p*100.0/f, "%");
             }
         }, cast(shared)&i, filesize);
     for (; i < filesize; ++i) {
         // Process
     }
     progress.send(0); // Stop
}

There's a cast to shared there which may be suboptimal, but since 
the progress thread is only reading it, I would say it's ok.

--
   Simen