Author: Dann Corbit
Date: 16:59:21 01/19/05
Go up one level in this thread
On January 19, 2005 at 19:43:53, Aaron Gordon wrote:
>On January 19, 2005 at 19:11:10, Dann Corbit wrote:
>
>>On January 19, 2005 at 17:56:42, Aaron Gordon wrote:
>>
>>>On January 19, 2005 at 17:46:32, Dann Corbit wrote:
>>>
>>>>On January 19, 2005 at 17:27:57, Aaron Gordon wrote:
>>>>
>>>>>On January 19, 2005 at 11:55:43, Rémi Coulom wrote:
>>>>>
>>>>>>Hi,
>>>>>>
>>>>>>I am porting my chess program to 64 bit on an AMD64 Athlon processor. I have
>>>>>>noticed that, with gcc, sizeof(int)=4. I would have expected sizeof(int)=8. On
>>>>>>32-bit platforms, 32-bit variables are faster than 16-bit variables. I wonder if
>>>>>>64-bit variables are faster than 32-bit variables on 64-bit machines. I have
>>>>>>made a few experiments and did not notice much difference.
>>>>>>
>>>>>>Rémi
>>>>>
>>>>>Try using longs instead of ints. I have a DEC Alpha 21164 here (64bit also), and
>>>>>wondered the same thing. Here is the output I got when running sizeof().
>>>>>
>>>>>short = 2 (16 bits)
>>>>>int = 4 (32 bits)
>>>>>long = 8 (64 bits)
>>>>>long long = 8 (64 bits)
>>>>>float = 4 (32 bits)
>>>>>double = 8 (64 bits)
>>>>>
>>>>>On my Athlon XP, as expected, I get:
>>>>>short = 2 (16 bits)
>>>>>int = 4 (32 bits)
>>>>>long = 4 (32 bits)
>>>>>long long = 8 (64 bits)
>>>>>float = 4 (32 bits)
>>>>>double = 8 (64 bits)
>>>>
>>>>Depends on the compiler you use too.
>>>>
>>>>A compiler vendor can use any type they want for int, as long as it will hold
>>>>+/- 32767 or larger.
>>>
>>>The only ones I've tested so far have been GCC (DGJPP and MingW), the Intel C
>>>compiler, MSVC and the Compaq C compiler (for the Alpha). Though I think
>>>MSVC/Intel C (windows) uses __int64 instead of long/longlong. So far though it
>>>seems like all the linux compilers treat a long as 32bits unless you have a
>>>64bit cpu & 64bit compiler. I'm guessing/hoping it would be alright to just use
>>>longs from now on and if you have a 64bit cpu you'll just get the benefit from a
>>>recompile.
>>>
>>>Just wishful thinking perhaps ;)
>>
>>On the Alpha (for instance) the DEC/COMPAQ/HP C++ compiler uses ints and longs
>>of 32 bits, like the MS compiler. For example:
>>
>>$ cxx s.c
>>$ link s
>>$ run s
>>sizeof char is by definition 1. This machine reports 1
>>sizeof int is 4
>>sizeof long is 4
>>sizeof long long is 8
>>$ type s.c
>>#include <stdio.h>
>>int main(void)
>>{
>> printf("sizeof char is by definition 1. This machine reports %u\n",
>>(unsigned) sizeof (char));
>> printf("sizeof int is %u\n", (unsigned) sizeof (int));
>> printf("sizeof long is %u\n", (unsigned) sizeof (long));
>>#ifdef __GNUC__
>> printf("sizeof long long is %u\n", (unsigned) sizeof (long long));
>>#else
>> printf("sizeof long long is %u\n", (unsigned) sizeof (__int64));
>>#endif
>> return 0;
>>}
>>$
>>
>>The GCC compiler on the same platform will report different values.
>
>What version of the Compaq C compiler are you using? I believe mine is
>6.5.6.002-1. It reports a long as 64 bits (same as my copy of GCC).
It's a fossil. We are in the process of updating right now, since this one does
not even understand template instantiation.
DEC C++ V5.0-003 on OpenVMS Alpha V6.2
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