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

David T. Lewis lewis at mail.msen.com
Tue Sep 1 00:21:46 UTC 2015


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.

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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