[Vm-dev] Re: [squeak-dev] ByteArray accessors for 64-bit manipulation

Tobias Pape Das.Linux at gmx.de
Tue Sep 1 05:51:29 UTC 2015


On 01.09.2015, at 02:21, David T. Lewis <lewis at mail.msen.com> wrote:

> 
> I would ask that someone please measure the real-world performance benefit
> of adding these (or any other) numbered primitives. Maybe it's a lot, maybe
> it's not, but when in doubt leave it out.

+1

> 
> Dave
> 
> On Mon, Aug 31, 2015 at 10:25:59AM -0700, Eliot Miranda wrote:
>> Hi Chrises,
>> 
>>    my vote would be to write these as 12 numbered primitives, (2,4 & 8
>> bytes) * (at: & at:put:) * (big & little endian) because they can be
>> performance critical and implementing them like this means the maximum
>> efficiency in both 32-bit and 64-bit Spur, plus the possibility of the JIT
>> implementing the primitives.
>> 
>> On Sun, Aug 30, 2015 at 10:01 PM, Chris Cunningham <cunningham.cb at gmail.com>
>> wrote:
>> 
>>> Hi Chris,
>>> 
>>> I'm all for having the fastest that in the image that works.  If you could
>>> make your version handle endianess, then I'm all for including it (at least
>>> in the 3 variants that are faster).  My first use for this (interface for
>>> KAFKA) apparently requires bigEndianess, so I really want that supported.
>>> 
>>> It might be best to keep my naming, though - it follows the name pattern
>>> that is already in the class.  Or will yours also support 128?
>>> 
>>> -cbc
>>> 
>>> On Sun, Aug 30, 2015 at 2:38 PM, Chris Muller <asqueaker at gmail.com> wrote:
>>> 
>>>> Hi Chris, I think these methods belong in the image with the fastest
>>>> implementation we can do.
>>>> 
>>>> I implemented 64-bit unsigned access for Ma Serializer back in 2005.
>>>> I modeled my implementation after Andreas' original approach which
>>>> tries to avoid LI arithmetic.  I was curious whether your
>>>> implementations would be faster, because if they are then it could
>>>> benefit Magma.  After loading "Ma Serializer" 1.5 (or head) into a
>>>> trunk image, I used the following script to take comparison
>>>> measurements:
>>>> 
>>>> | smallN largeN maBa cbBa |  smallN := ((2 raisedTo: 13) to: (2
>>>> raisedTo: 14)) atRandom.
>>>> largeN := ((2 raisedTo: 63) to: (2 raisedTo: 64)) atRandom.
>>>> maBa := ByteArray new: 8.
>>>> cbBa := ByteArray new: 8.
>>>> maBa maUint: 64 at: 0 put: largeN.
>>>> cbBa unsignedLong64At: 1 put: largeN bigEndian: false.
>>>> self assert: (cbBa maUnsigned64At: 1) = (maBa unsignedLong64At: 1
>>>> bigEndian: false).
>>>> { 'cbc smallN write' -> [ cbBa unsignedLong64At: 1 put: smallN
>>>> bigEndian: false] bench.
>>>> 'ma smallN write' -> [cbBa maUint: 64 at: 0 put: smallN ] bench.
>>>> 'cbc smallN access' -> [ cbBa unsignedLong64At: 1 bigEndian: false. ]
>>>> bench.
>>>> 'ma smallN access' -> [ cbBa maUnsigned64At: 1] bench.
>>>> 'cbc largeN write' -> [ cbBa unsignedLong64At: 1 put: largeN
>>>> bigEndian: false] bench.
>>>> 'ma largeN write' -> [cbBa maUint: 64 at: 0 put: largeN ] bench.
>>>> 'cbc largeN access' -> [ cbBa unsignedLong64At: 1 bigEndian: false ]
>>>> bench.
>>>> 'ma largeN access' -> [ cbBa maUnsigned64At: 1] bench.
>>>> }
>>>> 
>>>> Here are the results:
>>>> 
>>>> 'cbc smallN write'->'3,110,000 per second.  322 nanoseconds per run.' .
>>>> 'ma smallN write'->'4,770,000 per second.  210 nanoseconds per run.' .
>>>> 'cbc smallN access'->'4,300,000 per second.  233 nanoseconds per run.' .
>>>> 'ma smallN access'->'16,400,000 per second.  60.9 nanoseconds per run.' .
>>>> 'cbc largeN write'->'907,000 per second.  1.1 microseconds per run.' .
>>>> 'ma largeN write'->'6,620,000 per second.  151 nanoseconds per run.' .
>>>> 'cbc largeN access'->'1,900,000 per second.  527 nanoseconds per run.' .
>>>> 'ma largeN access'->'1,020,000 per second.  982 nanoseconds per run.'
>>>> 
>>>> It looks like your 64-bit access is 86% faster for accessing the
>>>> high-end of the 64-bit range, but slower in the other 3 metrics.
>>>> Noticeably, it was only 14% as fast for writing the high-end of the
>>>> 64-bit range, and similarly as much slower for small-number access..
>>>> 
>>>> 
>>>> On Fri, Aug 28, 2015 at 6:01 PM, Chris Cunningham
>>>> <cunningham.cb at gmail.com> wrote:
>>>>> Hi.
>>>>> 
>>>>> I've committed a change to the inbox with changes to allow
>>>> getting/putting
>>>>> 64bit values to ByteArrays (similar to 32 and 16 bit accessors).  Could
>>>> this
>>>>> be added to trunk?
>>>>> 
>>>>> Also, first time I used the selective commit function - very nice!  the
>>>>> changes I didn't want committed didn't, in fact, get commited.  Just the
>>>>> desirable bits!
>>>>> 
>>>>> -cbc
>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>>> 
>>> 
>>> 
>> 
>> 
>> -- 
>> _,,,^..^,,,_
>> best, Eliot




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