rdmd takes 2-3 seconds on a first-run of a simple .d script

[Andre Pany]

On Saturday, 25 May 2019 at 08:32:08 UTC, BoQsc wrote:
>> rdmd is a companion to the dmd compiler that simplifies the 
>> typical edit-compile-link-run or edit-make-run cycle to a 
>> rapid edit-run cycle. Like make and other tools, rdmd uses the 
>> relative dates of the files involved to minimize the amount of 
>> work necessary. Unlike make, rdmd tracks dependencies and 
>> freshness without requiring additional information from the 
>> user.
>
>> Source: https://dlang.org/rdmd.html
>
> I have a simple standard .d script and I'm getting annoyed that 
> it takes 2-3 seconds to run and see the results via rdmd.
>
> This might sound like insanely laughable time to be annoyed by, 
> but it is a enough of a problem for me to make a Thread in a D 
> lang Forum.
>
> Every time I make a change to a script it takes at least 2 
> seconds on my computer for it to run, if you are beginner like 
> me - you know it is not very pleasant to wait out that 
> duration. I wonder if anything can be done about it, why it 
> takes so "much" time, and why can't the results show up in a 
> few milliseconds instead?
>
> #!/usr/bin/env rdmd
> import std.stdio, std.process;
>
> void main() {
>
> 	writeln("This writeln is taking long time ");
> 	executeShell("pause");
>
> }

If I remember correctly:
rdmd does one step in the compilation step twice and is therefore 
slower than dmd.
Dmd was in the meantime enhanced to provide the same 
functionality as rdmd.
I assume dmd -i -run myscript.d
If you have one file only, you do not need the -i argument.

Also please keep in mind there could be other factors like slow 
disks, anti virus scanners,... which causes a slow down.

Dmd also allows you to just test the syntax of your source code 
file without generating an executable.

Kind regards
Andre