[squeak-dev] ByteArray accessors for 64-bit manipulation

Chris Cunningham cunningham.cb at gmail.com
Mon Aug 31 05:01:01 UTC 2015


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
> >
> >
> >
>
>
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