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digitalmars.D.bugs - Program hangs on Windows - DMD 0.99

reply Dave <Dave_member pathlink.com> writes:
Windows 2003 Server
DMD 0.99 (also 0.98)

The following program will hang on return from main when it is run with an
argument of >= 8388607. An argument of <= 8388606 will /not/ 'hang'. This is
consistent and repeatable on this platform.

The program does not hang like this using DMD for Linux. The program does still
hang when the Timer() and printf(...)'s are removed. 

On Windows at least, the concatenation also takes ~50% longer to complete the
concatenation when the iterations move from 8388606 to 8388607.

;---

import timer;
import std.string;
import std.outbuffer;

int main(char[][] args)
{
int n = args.length < 2 ? 1 : std.string.atoi(args[1]);

Timer t = new Timer();

OutBuffer ob = new OutBuffer();

for (int i = 0; i < n; i++)
ob.write("hello\n");

printf("%d\n", ob.toString().length);

printf("%.*s\n",t.Elapsed());

return(0);
}

;---

import std.date;
import std.string;
import std.outbuffer;

class Timer {
this() { tvs = getUTCtime(); }
char[] Elapsed() {
tve = getUTCtime();
OutBuffer ob = new OutBuffer;
ob.printf(" %2.6f seconds",(tve - tvs) / cast(double)TicksPerSecond);
return(ob.toString());
}
private:
d_time tvs, tve;
}
Aug 20 2004
next sibling parent pragma <EricAnderton at yahoo dot com> <pragma_member pathlink.com> writes:
I just tested this on my machine (WindowsXP-SP1) and got the same results. 

For grins, I opened Task Manager and enabled all the columns to see what was
going on.  At the point where it 'hangs', the memory useage was counting upwards
at phenomenal rate along with the page faults.  With my Task Manager set on
"high" as its refresh rate, i was seeing a difference of 200Kb of memory and
70-odd faults per update.

- Pragma

In article <cg4vmc$bj1$1 digitaldaemon.com>, Dave says...
Windows 2003 Server
DMD 0.99 (also 0.98)

The following program will hang on return from main when it is run with an
argument of >= 8388607. An argument of <= 8388606 will /not/ 'hang'. This is
consistent and repeatable on this platform.

The program does not hang like this using DMD for Linux. The program does still
hang when the Timer() and printf(...)'s are removed. 

On Windows at least, the concatenation also takes ~50% longer to complete the
concatenation when the iterations move from 8388606 to 8388607.

;---

import timer;
import std.string;
import std.outbuffer;

int main(char[][] args)
{
int n = args.length < 2 ? 1 : std.string.atoi(args[1]);

Timer t = new Timer();

OutBuffer ob = new OutBuffer();

for (int i = 0; i < n; i++)
ob.write("hello\n");

printf("%d\n", ob.toString().length);

printf("%.*s\n",t.Elapsed());

return(0);
}

;---

import std.date;
import std.string;
import std.outbuffer;

class Timer {
this() { tvs = getUTCtime(); }
char[] Elapsed() {
tve = getUTCtime();
OutBuffer ob = new OutBuffer;
ob.printf(" %2.6f seconds",(tve - tvs) / cast(double)TicksPerSecond);
return(ob.toString());
}
private:
d_time tvs, tve;
}

Aug 20 2004
prev sibling parent reply "Walter" <newshound digitalmars.com> writes:
It's apparently thrashing itself to death. Try using OutBuffer.reserve().

"Dave" <Dave_member pathlink.com> wrote in message
news:cg4vmc$bj1$1 digitaldaemon.com...
 Windows 2003 Server
 DMD 0.99 (also 0.98)

 The following program will hang on return from main when it is run with an
 argument of >= 8388607. An argument of <= 8388606 will /not/ 'hang'. This

 consistent and repeatable on this platform.

 The program does not hang like this using DMD for Linux. The program does

 hang when the Timer() and printf(...)'s are removed.

 On Windows at least, the concatenation also takes ~50% longer to complete

 concatenation when the iterations move from 8388606 to 8388607.

 ;---

 import timer;
 import std.string;
 import std.outbuffer;

 int main(char[][] args)
 {
 int n = args.length < 2 ? 1 : std.string.atoi(args[1]);

 Timer t = new Timer();

 OutBuffer ob = new OutBuffer();

 for (int i = 0; i < n; i++)
 ob.write("hello\n");

 printf("%d\n", ob.toString().length);

 printf("%.*s\n",t.Elapsed());

 return(0);
 }

 ;---

 import std.date;
 import std.string;
 import std.outbuffer;

 class Timer {
 this() { tvs = getUTCtime(); }
 char[] Elapsed() {
 tve = getUTCtime();
 OutBuffer ob = new OutBuffer;
 ob.printf(" %2.6f seconds",(tve - tvs) / cast(double)TicksPerSecond);
 return(ob.toString());
 }
 private:
 d_time tvs, tve;
 }

Aug 20 2004
parent "Dave" <Dave_member pathlink.com> writes:
It's not necessarily the performance I'm concerned about, but that was just
one more symptom I noticed so I included that info.

I realize the program is contrived and trivial, but I think it may point to
a potential problem in the memory management system. As Pragma pointed out
with his Task Manager info., there is definately something odd going on.

If I put an explicit fullCollect() before the return and the buffer size
grows beyond 50_331_636, the fullCollect() itself takes several minutes to
return and Task Manager shows the same symptoms Pragma noted for the return
from main in the original code.

This and the arbitrary buffer size that causes the problem is really the
'bug' I was trying to point out.

Also, if:

ob.reserve(10);

is added before the loop and the program is run for 10_000_000 iterations,
the problem (and slower performance) goes away for some reason until the
iterations grow to >= 10_400_000.

If reserve is changed to:

ob.reserve(100000);

the same problem reappears for the same number of iterations (10_000_000).

Given the seemingly arbitrary nature of this, I think there is a problem
here. If a garbage collection causes this kind of hang under heavy use in
the real world under some conditions, it would be a major problem I would
think <g>.

The 1/3 performance drop when the iterations move from 8388606 to 8388607
happens on Linux too. The difference is that fullCollect() doesn't hang on
Linux.

- Dave

"Walter" <newshound digitalmars.com> wrote in message
news:cg6gkr$158t$1 digitaldaemon.com...
 It's apparently thrashing itself to death. Try using OutBuffer.reserve().

 "Dave" <Dave_member pathlink.com> wrote in message
 news:cg4vmc$bj1$1 digitaldaemon.com...
 Windows 2003 Server
 DMD 0.99 (also 0.98)

 The following program will hang on return from main when it is run with


 argument of >= 8388607. An argument of <= 8388606 will /not/ 'hang'.


 is
 consistent and repeatable on this platform.

 The program does not hang like this using DMD for Linux. The program


 still
 hang when the Timer() and printf(...)'s are removed.

 On Windows at least, the concatenation also takes ~50% longer to


 the
 concatenation when the iterations move from 8388606 to 8388607.

 ;---

 import timer;
 import std.string;
 import std.outbuffer;

 int main(char[][] args)
 {
 int n = args.length < 2 ? 1 : std.string.atoi(args[1]);

 Timer t = new Timer();

 OutBuffer ob = new OutBuffer();

 for (int i = 0; i < n; i++)
 ob.write("hello\n");

 printf("%d\n", ob.toString().length);

 printf("%.*s\n",t.Elapsed());

 return(0);
 }

 ;---

 import std.date;
 import std.string;
 import std.outbuffer;

 class Timer {
 this() { tvs = getUTCtime(); }
 char[] Elapsed() {
 tve = getUTCtime();
 OutBuffer ob = new OutBuffer;
 ob.printf(" %2.6f seconds",(tve - tvs) / cast(double)TicksPerSecond);
 return(ob.toString());
 }
 private:
 d_time tvs, tve;
 }


Aug 21 2004