Ok, more performance ;) The SwapInt() method is now 40% faster than when i
originally started and SwapLong() is now 50% faster than the original
method. This means i do 15 iterations of converting a long in 8500ms, which
isn't that much slower than the MS one (6700ms)
All i did this time was remove the extra bit shifts. Instead of shifting
across by 48, then &'ing then shifting back by 8 i just shifted across by 40
and &'ed there.
Patch attached. Let me know if it's OK to commit.
Alan.
On 3/25/07, Gareth Pearce <[EMAIL PROTECTED]> wrote:
>
> >
> > However, as a comparison, the MS.NET <http://MS.NET>
> <http://MS.NET> implementation
> > completes 15 loops of the benchmark in a mere 6718ms ;)
> >
>
On this point, I suspect AOT compilation of the .Net system assemblies
may be making the difference. The AOT might be able to recognize
certain patterns are equivalent to rot instructions and replace a bunch
of shifts and masks with a set of unsigned rots.
A 32bit reorder is rot 8 on each of the 16 bit sections and a rot 16 on
the full variable. I think that can be done in 3 clocks on x86 - but my
assembly is rusty.
--Gareth
Index: C:/programming/mcs/class/System/System.Net/IPAddress.cs
===================================================================
--- C:/programming/mcs/class/System/System.Net/IPAddress.cs (revision 74942)
+++ C:/programming/mcs/class/System/System.Net/IPAddress.cs (working copy)
@@ -58,7 +58,7 @@
private static short SwapShort (short number)
{
- return (short) ( ((number >> 8) & 0xFF) + ((number << 8) & 0xFF00) );
+ return (short) ( ((number >> 8) & 0xFF) | ((number << 8) & 0xFF00) );
}
private static int SwapInt (int number)
@@ -64,22 +64,22 @@
private static int SwapInt (int number)
{
return ((number >> 24) & 0xFF)
- + (((number >> 16) & 0xFF) << 8)
- + (((number >> 8) & 0xFF) << 16)
- + ((number & 0xFF) << 24);
+ | (((number >> 8) & 0xFF00))
+ | (((number << 8) & 0xFF0000))
+ | (((number & 0xFF) << 24));
}
- private static long SwapLong(long number)
- {
- return (((number >> 56) & 0xFF)
- + (((number >> 48) & 0xFF) << 8)
- + (((number >> 40) & 0xFF) << 16)
- + (((number >> 32) & 0xFF) << 24)
- + (((number >> 24) & 0xFF) << 32)
- + (((number >> 16) & 0xFF) << 40)
- + (((number >> 8) & 0xFF) << 48)
- + ((number & 0xFF) << 56));
- }
+ private static long SwapLong(long number)
+ {
+ return (((number >> 56) & 0xFF)
+ | (((number >> 40) & 0xFF00))
+ | (((number >> 24) & 0xFF0000))
+ | (((number >> 8) & 0xFF000000))
+ | (((number << 8) & 0xFF00000000))
+ | (((number << 24) & 0xFF0000000000))
+ | (((number << 40) & 0xFF000000000000))
+ | ((number & 0xFF) << 56));
+ }
public static short HostToNetworkOrder(short host) {
if (!BitConverter.IsLittleEndian)
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