memory surprise; help a struggling newbie

[Travis Griggs]

From the irc channel the other day, I was under the impression that 
factory methods do an implicit AUTORELEASE. But I noticed that operating 
on that assumption, my C-program-infected with objc, seemed to be 
growing in memory usage, watching it with top at least. So I threw 
together the attached simple program. I'm running with debian 
gnustep-base1 here, and gobc 3.3.3, both from the testing branch.

Running the ./memLoop program, watching it under top, it does indeed 
grow, after about 2 minutes of wall clock time, linux kills it because 
its 500+ MB. What am I missing? The only real object allocation should 
be the duplicate strings created over and over and over again. I even 
tried adding the redundant AUTORELEASE(key); line, but still to no 
avail. I compiled with -o0, thinking the compiler was inlining my 
function, thus causing the ARP to never change stack frames and never 
release. Still, no improvement. I'm wondering if there's something wrong 
with stringWithFormat:.

------

On another note, and this is a bit of an apples-2-oranges comparison, 
but I'd like to understand it better. Even before this program runs out 
of memory, even when it hasn't used up much yet... VisualWorks Smalltalk 
beats it out by nearly 2:1 speed wise. I ran both programs, letting 
their interval counter run up to 100000, the inner loop creating 100 
keys and adding them to the dictionary, this makes for ten million 
object allocations. VW did it in 55 seconds (lowly 800 Mhz Duron here). 
memLoop (the attached objc program) took 99 seconds. The VW snippet 
looks like:

| dict interval staticValue |
dict := Dictionary new.
interval := 0.
staticValue := 'BigStaticString'.

[1 to: 100 do: [:i | dict at: 'key' , i printString put: staticValue].
interval := interval + 1.
interval \\ 10000 = 0 ifTrue: [interval out]]
                repeat

This leads me further to believe that its the stringWithFormat: that is 
causing the real problem, because that's the real difference. The 
Smalltalk VM's memory usage under top didn't budge during the test btw.

--
Travis Griggs
Objologist
Key Technology
Achille's Heel?!?! What about "Goliath's Forehead"



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#include <Foundation/Foundation.h> 
#include <stdint.h> 
#include <unistd.h> 

NSString* staticString = @"BigSharedEntry";

void addEntriesTo(NSMutableDictionary* theDictionary)
{
        int32_t i;

        for(i = 0; i < 100; i++)
        {
                NSString* key = [NSString stringWithFormat: @"key%d", i];
                AUTORELEASE(key);
                [theDictionary setObject: staticString forKey: key];
        }
}

int32_t main(int32_t argc, char** argv)
{
        CREATE_AUTORELEASE_POOL(pool);
        NSMutableDictionary* theDictionary = [NSMutableDictionary new];
        
        int32_t interval = 0;
        while(1)
        {
                addEntriesTo(theDictionary);
                interval++;
                if((interval % 10000) == 0)
                {
                        printf("%u\n", interval);
                }
        }
        [pool release];
}

OBJS=  memLoop.o

CFLAGS = -g -O0 -Wall -fno-strict-aliasing -D_REENTRANT 
-DVERSION=\"$(VERSION)\" 
LIBS =  -lobjc -L/usr/lib/GNUstep/System/Library/Libraries -lgnustep-base

all:    $(OBJS) 
        gcc $(CFLAGS)  -o memLoop $(OBJS) $(LIBS)

.c.o: 
        gcc -c -x objective-c -fconstant-string-class=NSConstantString 
-I/usr/lib/GNUstep/System/Library/Headers $(CFLAGS) $<