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digitalmars.D.learn - Static array size limit

reply simendsjo <simen.endsjo pandavre.com> writes:
http://digitalmars.com/d/2.0/arrays.html says static arrays are
limited to 16mb, but I can only allocate 1mb.
My fault, or bug?

	enum size = (16 * 1024 * 1024) / int.sizeof;
	//int[size] a;   // Error: index 4194304 overflow for static
array
	enum size2 = (16 * 1000 * 1000) / int.sizeof;
	//int[size2] b; // Stack Overflow
	//int[250_001] c; // Stack Overflow
	int[250_000] d; // ok
Apr 02 2011
next sibling parent simendsjo <simen.endsjo pandavre.com> writes:
This is using dmd 2.052 on windows by the way.
Apr 02 2011
prev sibling next sibling parent reply Jonathan M Davis <jmdavisProg gmx.com> writes:
On 2011-04-02 06:21, simendsjo wrote:

 http://digitalmars.com/d/2.0/arrays.html says static arrays are
 limited to 16mb, but I can only allocate 1mb.
 My fault, or bug?
 
 	enum size = (16 * 1024 * 1024) / int.sizeof;
 	//int[size] a;   // Error: index 4194304 overflow for static
 array
 	enum size2 = (16 * 1000 * 1000) / int.sizeof;
 	//int[size2] b; // Stack Overflow
 	//int[250_001] c; // Stack Overflow
 	int[250_000] d; // ok


Well, 16 * 1024 * 1024 certainly isn't going to work when it's an array ints. 
An int is 4 bytes. So, the max would be more like 4 * 1024 * 1024, and that's 
assuming no overhead (which there may or may not be). Now, 4 * 1024 * 1024 is 
4_194_304, which is definitely more than 250_000, so if 16mb is indeed the 
limit, I don't know why you can't create one greater than 250_000, but you're 
_not_ going to be able to create one of length 16 * 1024 * 10243. That would 
be 64mb.

- Jonathan M Davis
Apr 02 2011
parent simendsjo <simen.endsjo pandavre.com> writes:
I think you missed my "/int.sizeof" at the end.

enum size = (16*1024*1024)/int.sizeof;
int[size] a; // "Error index overflow for static" as expected
int[size-1] b; // stack overflow
int[250_001] c; // stack overflow
int[250_000] d; // ok
Apr 02 2011
prev sibling parent reply bearophile <bearophileHUGS lycos.com> writes:
simendsjo:


 http://digitalmars.com/d/2.0/arrays.html says static arrays are
 limited to 16mb, but I can only allocate 1mb.
 My fault, or bug?


It accepts 4_000_000 ints, but not (16 * 1024 * 1024) / int.sizeof = 4_194_304
ints. I don't know why it's designed this way... I'd like 4_194_304 ints.

Bye,
bearophile
Apr 02 2011
next sibling parent reply simendsjo <simen.endsjo pandavre.com> writes:
On 02.04.2011 16:45, bearophile wrote:

 simendsjo:


 http://digitalmars.com/d/2.0/arrays.html says static arrays are
 limited to 16mb, but I can only allocate 1mb.
 My fault, or bug?


 It accepts 4_000_000 ints, but not (16 * 1024 * 1024) / int.sizeof = 4_194_304
ints. I don't know why it's designed this way... I'd like 4_194_304 ints.

 Bye,
 bearophile


The main problem is that it gives a Stack Overflow already at 250_001
Apr 02 2011
parent bearophile <bearophileHUGS lycos.com> writes:
simendsjo:


 The main problem is that it gives a Stack Overflow already at 250_001


I meant with the array as a global variable.
The stack on Windows can be set very large too, with -L/STACK:10000000

Bye,
bearophile
Apr 02 2011
prev sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Sat, 02 Apr 2011 10:45:51 -0400, bearophile <bearophileHUGS lycos.com>  
wrote:


 simendsjo:


 http://digitalmars.com/d/2.0/arrays.html says static arrays are
 limited to 16mb, but I can only allocate 1mb.
 My fault, or bug?


 It accepts 4_000_000 ints, but not (16 * 1024 * 1024) / int.sizeof =  
 4_194_304 ints. I don't know why it's designed this way... I'd like  
 4_194_304 ints.


That would be 16 MiB.

http://en.wikipedia.org/wiki/Mebibyte

-Steve
Apr 04 2011
next sibling parent reply bearophile <bearophileHUGS lycos.com> writes:
Steven Schveighoffer:


 That would be 16 MiB.
 
 http://en.wikipedia.org/wiki/Mebibyte


Then I think 16 MiB are more useful than 16_000_000 bytes.

Bye,
bearophile
Apr 04 2011
parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Mon, 04 Apr 2011 12:43:03 -0400, bearophile <bearophileHUGS lycos.com>  
wrote:


 Steven Schveighoffer:


 That would be 16 MiB.

 http://en.wikipedia.org/wiki/Mebibyte


 Then I think 16 MiB are more useful than 16_000_000 bytes.


Seems arbitrary to me.  I'm sure some people feel 32MB would be more  
useful.

-Steve
Apr 04 2011
prev sibling parent reply Jonathan M Davis <jmdavisProg gmx.com> writes:
On 2011-04-04 06:37, Steven Schveighoffer wrote:

 On Sat, 02 Apr 2011 10:45:51 -0400, bearophile <bearophileHUGS lycos.com>
 
 wrote:

 simendsjo:

 http://digitalmars.com/d/2.0/arrays.html says static arrays are
 limited to 16mb, but I can only allocate 1mb.
 My fault, or bug?


 
 It accepts 4_000_000 ints, but not (16 * 1024 * 1024) / int.sizeof =
 4_194_304 ints. I don't know why it's designed this way... I'd like
 4_194_304 ints.


 
 That would be 16 MiB.
 
 http://en.wikipedia.org/wiki/Mebibyte


Most of the time that anyone talks about megabytes, they mean mebibytes, so I 
think that it's unrealistic to expect that anyone is going to see 16MB and 
think that it means 16_000_000 bytes reather than 16_777_216 bytes.

- Jonathan M Davis
Apr 04 2011
parent simendsjo <simen.endsjo pandavre.com> writes:
And it seems also Walter is meaning mebibytes:

enum size = (16*1024*1024)/int.sizeof;
static assert(!__traits(compiles, int[size]));
static assert(__traits(compiles, int[size-1]));
Apr 04 2011