Hello,
R version 2.4.1 (2006-12-18)
i386-pc-mingw32
Calling serialize() with a NULL connection serializes it to a raw vector.
However, when the object to be serialized is large, it takes a very long time:
> system.time( serialize(matrix(0, 1000, 1000), NULL) )
[1] 38.25 40.73 81.54 NA NA
> system.time( serialize(matrix(0, 2000, 2000), NULL) )
[1] 609.72 664.75 1318.57 NA NA
I was using this in Rmpi, where a clustered call returned a large matrix.
However, serializing to a file or sockets is very fast for the very same matrix
-- hence I wrote this function which runs much faster:
.mpi.quick.serialize <- function (object)
{
fname <- tempfile("Rmpi")
stream <- file(fname, "wb")
on.exit({
close(stream)
file.remove(fname)
})
serialize(object, stream)
close(stream)
size <- file.info(fname)$size
stream <- file(fname, "rb")
return(readBin(stream, "raw", n = size))
}
> system.time( .mpi.quick.serialize(matrix(0, 1000, 1000) ) )
[1] 0.2500000000000000 0.0499999999999545 0.3000000000001819
[4] NA NA
> system.time( .mpi.quick.serialize(matrix(0, 2000, 2000) ) )
[1] 1.059999999999945 0.220000000000027 1.289999999999964
[4] NA NA
Does anyone have an idea why the performance difference is so
large? Also, I was wondering if there is a better way -- the
above solution feels like a quick fix rather than a correct
approach.
Regards,
ashish
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