[Rd] serialize() takes too long when serializing to a raw vector

[Hin-Tak Leung]

Ashish Kulkarni wrote:
> 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

<snipped>
>> 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.

It might be interesting to know get some details on your hardware.

On my box, linux native seems to be a little slower than
your quick.serialize times:

 > system.time( serialize(matrix(0, 1000, 1000), NULL) )
[1] 0.372 0.288 0.692 0.000 0.000
 > system.time( serialize(matrix(0, 2000, 2000), NULL) )
[1] 1.237 1.195 2.501 0.000 0.000

running R 2.4.1 windows under wine (same box) is a good deal s
lower, but is not anywhere nearly as slow as yours.

 > system.time( serialize(matrix(0, 1000, 1000), NULL) )
[1] 0.00 0.00 6.08   NA   NA
 > system.time( serialize(matrix(0, 2000, 2000), NULL) )
[1]  0.01  0.01 78.00    NA    NA
 >

Since you mentioned that you are using Rmpi, there is a possibility
that you might be calling a different serialize() than base::serialize
all together???