[R] rJava call performance

[Dmitriy Lyubimov]

The "low level" seems to be much-much better though... not sure why
the difference would be so fundamental...

f <- function() system.time( for( i in 1:1000)
.jcall("java/lang/Math", returnSig="D", "abs", as.numeric(i) ) )
> f()
   user  system elapsed
  0.080   0.000   0.083


On Fri, Mar 16, 2012 at 3:27 PM, Dmitriy Lyubimov <dlieu.7 at gmail.com> wrote:
> PS caching reference to the class doesn't change anything fundamentally:
>
> clazz <- J("java.lang.Double")
> system.time( for( i in 1:1000) clazz$ parseDouble(as.character(i)))
>   user  system elapsed
>  3.788   0.000   3.790
>
> Java parsing is slow??? nope, still looking pretty appalling for what it does:
>
>> clazz <- J("java.lang.Math")
>> system.time( for( i in 1:1000) clazz$abs(i) )
>   user  system elapsed
>  3.492   0.000   3.497
>
>
> On Fri, Mar 16, 2012 at 3:17 PM, Dmitriy Lyubimov <dlieu.7 at gmail.com> wrote:
>> Hello,
>>
>> I am getting pretty poor rJava call performance
>>
>>
>>> system.time(for (i in 1:1000) J("java.lang.Double")$parseDouble(as.character(i)))
>>   user  system elapsed
>>  4.884   0.000   4.900
>>
>>
>> i.e. 5 milliseconds per very simple call on a very fast cpu. JNI calls
>> themselves are said to be pretty fast nowadays (10...40ns). It
>> probably goes accross reflection but still doing pretty much nothing
>> useful in 5ms is horrible benchmark.
>>
>> Is that expected rJava performance? Cause if it is, this means it is
>> completely usuitable for exchanging data with Java. ( I can probably
>> bulk up data in data frames and pass it as a single call to do
>> something with it but then either way i have to do conversion between
>> bulk of R objects and bulk of java objects).
>>
>> Is there's a good performant way to do passing of data.frame's between
>> java and back without having to do a native call for every row?
>>
>> Thank you.
>> -Dmitriy