smallest type

[Bob]

Hi,
I have a newbie question. What is the smallest type object size? I am
doing some calculation with individual bits and want to minimize memory
usage. I though bool might do it but it seems like each bool is a
byte, instead of a bit. Is bool the smallest possible type?

Thanks,
Bob

[Dave Sexton]

Re: smallest type

Hi Bob,

Normally byte is used as the smallest integral data type.

--
Dave Sexton

http://davesexton.com/blog

http://www.codeplex.com/DocProject (Sandcastle in VS IDE)

"Bob" <bshumsky06@yah oo.comwrote in message
news:1169694026 .816069.173010@ m58g2000cwm.goo glegroups.com.. .

Hi,
I have a newbie question. What is the smallest type object size? I am
doing some calculation with individual bits and want to minimize memory
usage. I though bool might do it but it seems like each bool is a
byte, instead of a bit. Is bool the smallest possible type?
>
Thanks,
Bob
>

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

Re: smallest type

Bob wrote:

I have a newbie question. What is the smallest type object size? I am
doing some calculation with individual bits and want to minimize memory
usage. I though bool might do it but it seems like each bool is a
byte, instead of a bit. Is bool the smallest possible type?

If speed is important use byte else you can try the
System.Collecti ons.BitArray class.

Arne

[Dave Sexton]

Re: smallest type

In that case, BitVector32 is another alternative if you need to use flags or
small integers, "but it has the memory and performance overhead that a class
instance requires. In contrast [to BitArray], a BitVector32 uses only 32
bits" [1].

[1] BitVector32 Structure

http://msdn2.microsoft.com/en-us/library/system.collections.specialized.bitvector32.aspx

--
Dave Sexton

http://davesexton.com/blog

http://www.codeplex.com/DocProject (Sandcastle in VS IDE)

"Arne Vajhøj" <arne@vajhoej.d kwrote in message
news:45b82398$0 $49200$14726298 @news.sunsite.d k...

Bob wrote:

>I have a newbie question. What is the smallest type object size? I am
>doing some calculation with individual bits and want to minimize memory
>usage. I though bool might do it but it seems like each bool is a
>byte, instead of a bit. Is bool the smallest possible type?

>
If speed is important use byte else you can try the
System.Collecti ons.BitArray class.
>
Arne

[Bob]

Re: smallest type

Thanks for all the quick replies. By use byte, do you mean that an
byte[] where all the entries are either 0 or 1 will perform faster than
a similarly size bool[]?

Thanks,
Bob

On Jan 24, 9:27 pm, Arne Vajhøj <a...@vajhoej.d kwrote:

Bob wrote:

I have a newbie question. What is the smallest type object size? I am
doing some calculation with individual bits and want to minimize memory
usage. I though bool might do it but it seems like each bool is a
byte, instead of a bit. Is bool the smallest possible type?If speed isimportant use byte else you can try the

System.Collecti ons.BitArray class.

Arne

[Mattias Sjögren]

Re: smallest type

>By use byte, do you mean that an

>byte[] where all the entries are either 0 or 1 will perform faster than
>a similarly size bool[]?

I think they will perform pretty much the same, since bytes and bools
are usually treated the same way by the runtime. Both types are 1
byte.


Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Willy Denoyette [MVP]]

Re: smallest type

"Bob" <bshumsky06@yah oo.comwrote in message
news:1169694026 .816069.173010@ m58g2000cwm.goo glegroups.com.. .

Hi,
I have a newbie question. What is the smallest type object size? I am
doing some calculation with individual bits and want to minimize memory
usage. I though bool might do it but it seems like each bool is a
byte, instead of a bit. Is bool the smallest possible type?
>
Thanks,
Bob
>

It depends on what you mean with "object" size, the smallest *Reference type* size type is
an int.
byte b = 1;
object o = b;
here, o will take 12 bytes (on X86), 8 bytes object header plus 4 bytes for the byte value.

If you mean primitive type size, then by definition the smallest type is a byte, but again
it highly depends on where and how they are allocated.

void Foo()
{
byte b;
int i;
...

In above sample, both b and i will be stored on the stack, both i and b will occupy a slot
on the stack( Int32 on x86).
void Foo()
{
byte b;
int i;
byte b2;
byte b3,
byte b4;

In above, the four bytes will occupy a single slot (4 bytes on X86) just like i. so here the
same amount of memory is used as the previous sample.

class Foo{
byte b;
int i;
byte b2;
byte b3,
byte b4;
}

class Bar {
byte b;
int i;
}

Same here, An instance of Foo or Bar will occupy the same amount of memory, that is, 8
bytes header plus 8 bytes for the data members.
Conclusion, it makes little sense to use a smaller value than an int if you can't combine a
number of these small integer values.

Willy.

[Fabio Z]

Re: smallest type

"Mattias Sjögren" <mattias.dont.w ant.spam@mvps.o rgha scritto nel messaggio

I think they will perform pretty much the same, since bytes and bools
are usually treated the same way by the runtime. Both types are 1
byte.

mmm... I know that in .net a bool is a 4 bytes, and used as a Int32 in
compiled IL for compares.
And for performances a 4 bytes on a 32bits architecture is best over each
other lengths.
If the aim is a small flags data type use an enum x : byte

Personally I will avoid these thoughts about memory allocation in .Net, sice
it is fully managed by the famework and the garbage collector (also the data
in the taskmanager about .net apps are all lies).

[Mattias Sjögren]

Re: smallest type

>mmm... I know that in .net a bool is a 4 bytes

You do eh? And yet Console.WriteLi ne(sizeof(bool) ) prints 1.


Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Fabio]

Re: smallest type

"Mattias Sjögren" <mattias.dont.w ant.spam@mvps.o rgha scritto nel messaggio

>

>>mmm... I know that in .net a bool is a 4 bytes

>
You do eh? And yet Console.WriteLi ne(sizeof(bool) ) prints 1.
>

And my IL says that bool x = true is

L_0001: ldc.i4.1

i4 stays for Int32.
1 stays for the "true" value (0 is false).

And now? ;)

[Willy Denoyette [MVP]]

Re: smallest type

"Fabio" <znt.fabio@virg ilio.itwrote in message
news:%234oZrZLQ HHA.4172@TK2MSF TNGP04.phx.gbl. ..

"Mattias Sjögren" <mattias.dont.w ant.spam@mvps.o rgha scritto nel messaggio
>

>>

>>>mmm... I know that in .net a bool is a 4 bytes

>>
>You do eh? And yet Console.WriteLi ne(sizeof(bool) ) prints 1.
>>

>
And my IL says that bool x = true is
>
L_0001: ldc.i4.1
>
i4 stays for Int32.
1 stays for the "true" value (0 is false).
>
And now? ;)

Now ..... the ldc is not relevant, ldc does nothing else that storing the value 1 on the
execution stack (not to be confused with the real thread stack), what's important here is
the store instruction probably a stloc.0, where location 0 is a local variable declared as
bool.
Rest assured, a bool takes one byte in memory, but as I said in another reply all depends on
the context.

Willy.

[Fabio]

Re: smallest type

"Willy Denoyette [MVP]" <willy.denoyett e@telenet.beha scritto nel
messaggio news:%235J6C7LQ HHA.448@TK2MSFT NGP04.phx.gbl.. .

Now ..... the ldc is not relevant, ldc does nothing else that storing the
value 1 on the execution stack (not to be confused with the real thread
stack), what's important here is the store instruction probably a stloc.0,
where location 0 is a local variable declared as bool.

But there is some documentation about this?
I don't understand: why use a i4 instruction if it is only one byte?
IL would cause itsefl an umbalanced stack :)

Rest assured, a bool takes one byte in memory, but as I said in another
reply all depends on the context.

Yes, you're right.

[Barry Kelly]

Re: smallest type

Bob wrote:

Thanks for all the quick replies. By use byte, do you mean that an
byte[] where all the entries are either 0 or 1 will perform faster than
a similarly size bool[]?

BitArray should work with individual bits in a backing array, which
means it should be 8 times more efficient (in terms of space) than
bool[].

byte[] containing only 0 and 1 should perform about the same as bool[].

-- Barry

--

http://barrkel.blogspot.com/

[Barry Kelly]

Re: smallest type

Fabio wrote:

And my IL says that bool x = true is
>
L_0001: ldc.i4.1
>
i4 stays for Int32.
1 stays for the "true" value (0 is false).
>
And now? ;)

The CLI *stack* doesn't model bytes. It has only 6 types:

* 32-bit integer
* 64-bit integer
* native integer
* object
* floating-point number
* pointer type, without distinction as to what's being pointed to

The actual IL instructions permit more data types to be implemented in
terms of these primitives.

See ECMA 335 Partition III Section 1.1 for more details.

-- Barry

--

http://barrkel.blogspot.com/