Re: Memory allocation faile on string concat

[Steven Schveighoffer]

On Wed, 10 Nov 2010 11:33:45 -0500, Xie <xiema...@gmail.com> wrote:
Can't run a simple program. What's wrong, GC?

import std.stdio;
import std.date;

void f0()
{
        wstring a[];

        foreach(i; 0 .. 100_000_000)
        {
                a ~= " "w;
        }
}

void main()
{
        auto r = benchmark!(f0)(1);
        writeln(r, "ms");
}

The results on my machine with 1G of memory is that it consumes 2G of  
memory and the system starts thrashing.  I changed the value to  
10_000_000, and it runs in a couple seconds, I change it to 50_000_000 and  
it runs in 200 seconds.

Something is definitely amiss here, because the following doesn't help (it  
still consumes 1.2GB of memory):

void f0()
{
        wstring a[];
        a.reserve(100_000_000);

        foreach(i; 0 .. 100_000_000)
        {
                a ~= " "w;
        }
}

This should take the explosive nature of appending out of the equation,  
because a reallocation should never occur.

I'll look into it.

-Steve