Author: Tony Werten
Date: 05:26:17 03/18/05
Go up one level in this thread
On March 17, 2005 at 22:26:20, Dann Corbit wrote:
>On March 17, 2005 at 21:40:38, Robert Hyatt wrote:
>
>>On March 17, 2005 at 21:16:36, Dann Corbit wrote:
>>
>>>On March 17, 2005 at 17:07:15, Robert Hyatt wrote:
>>>
>>>>On March 17, 2005 at 14:47:24, Matthew Hull wrote:
>>>>
>>>>>I have two vanilla builds of GNUChess 5.07. One is in CYGWIN, the other in
>>>>>Linux. Both are on x86 architecture. But each allocates hash memory in
>>>>>different volumes.
>>>>>
>>>>>Example command:
>>>>>
>>>>>./gnuchess -s 10000000
>>>>>
>>>>>On Cygwin, this allocates 393216K of hash memory.
>>>>>
>>>>>On Linux, it allocates 327680K
>>>>>
>>>>>What is the reason for this?
>>>>
>>>>Several possibilities. But first, have you started both programs without the -s
>>>>option to see how big they are, then restarted both with the -s to see the
>>>>difference?
>>>
>>>Some other likely differences:
>>>
>>>1. structure packing (since the hash table seems to be an 'entries' count if
>>>the struct is aligned differently it will not be at all surprising if the same
>>>count of structs has different sizes on two machines.
>>>
>>>2. memory page sizes are different (small differences will be explained this
>>>way)
>>
>>On the PC the pagesize is 4K period. Unless you use the huge page-size which
>>most operating systems do not use (4mb for intel, I think AMD opteron supports a
>>2M page size as well).
>>
>>I can't imagine anyone with a hash entry size that is not a multiple of 4/8,
>>which would eliminate the packing issue on the X86 box...
>
>E:\pgn\WINBOA~1\GNUCHE~1.07\src>type foo.c
>#include <stdio.h>
>#include <stdlib.h>
>#include <string.h>
>#include "common.h"
>int main(void)
>{
> HashSlot hs;
> printf("sizeof HashSlot = %u\n", (unsigned) sizeof hs);
> return 0;
>}
>
>E:\pgn\WINBOA~1\GNUCHE~1.07\src>cl /Zp8 foo.c
>Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 13.10.3077 for 80x86
>Copyright (C) Microsoft Corporation 1984-2002. All rights reserved.
>
>foo.c
>Microsoft (R) Incremental Linker Version 7.10.3077
>Copyright (C) Microsoft Corporation. All rights reserved.
>
>/out:foo.exe
>foo.obj
>
>E:\pgn\WINBOA~1\GNUCHE~1.07\src>foo
>sizeof HashSlot = 24
>
>E:\pgn\WINBOA~1\GNUCHE~1.07\src>cl /Zp4 foo.c
>Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 13.10.3077 for 80x86
>Copyright (C) Microsoft Corporation 1984-2002. All rights reserved.
>
>foo.c
>Microsoft (R) Incremental Linker Version 7.10.3077
>Copyright (C) Microsoft Corporation. All rights reserved.
>
>/out:foo.exe
>foo.obj
>
>E:\pgn\WINBOA~1\GNUCHE~1.07\src>foo
>sizeof HashSlot = 20
I think it depends on wether the compiler default aligns structures on 4 byte or
8 byte.
Tony
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