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

Eliot Miranda eliot.miranda at gmail.com
Mon Aug 31 17:25:59 UTC 2015


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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