serialize/unserialize vector improvement

This has languished for a long time, and we should make a decision
before FF for 2.15.0.

It seems to me that in so far as there is a problem, it is that we
serialize via XDR, and that since that was invented little-endian CPUs
have taken over the world. So for the only cases I can imagine this is
really a problem (passing objects in 'parallel'/snow ... contexts) a
better answer might be to pass without byte-reordering: go back to the
RDB format which was exposed for save() but AFAIK never for serialize.

I would say Sparc is the only big-endian platform left (some PPC Mac
users may disagree), so little-endian really does rule.

Brian

On 03/10/2011 14:28, luke-tierney at uiowa.edu wrote:

It's on my list to look at but I may not get to it for a couple of
weeks. Someone else may get there earlier.

Best,

luke

On Mon, 3 Oct 2011, Michael Spiegel wrote:

Any thoughts? I haven't heard any feedback on this patch.

Thanks!
--Michael

On Wed, Sep 28, 2011 at 3:10 PM, Michael Spiegel
<michael.m.spiegel at gmail.com> wrote:

Hi folks,

I've attached a patch to the svn trunk that improves the performance
of the serialize/unserialize interface for vector types. The current
implementation: a) invokes the R_XDREncode operation for each element
of the vector type, and b) uses a switch statement to determine the
stream type for each element of the vector type. I've added
R_XDREncodeVector/R_XDRDecodeVector functions that accept N elements
at a time, and I've reorganized the implementation so that the stream
type is not queried once per element.

In the following microbenchmark (below), I've observed performance
improvements of about x2.4. In a real benchmark that is using the
serialization interface to make MPI calls, I see about a 10%
improvement in performance.

Cheers,
--Michael

microbenchmark:

input <- matrix(1:100000000, 10000, 10000)
output <- serialize(input, NULL)
for(i in 1:10) { print(system.time(serialize(input, NULL))) }
for(i in 1:10) { print(system.time(unserialize(output))) }