[Rd] JRI and error message from R_isMethodsDispatchOn

[Keith]

Hello Urbanek,

Simon Urbanek wrote:
> Keith,
> 
> On Nov 19, 2010, at 7:40 PM, Keith wrote:
> 
>> Dear R users,
>>
>> I have a small project written in Java and need some statical tools. Therefore, I used JRI (in rJava package) as an interface between R and Java to write some wrappers for my work. However, I received error message from R while I have more than one java method which wraps R:
>>
>> Error in .Call("R_isMethodsDispatchOn", onOff, PACKAGE = "base") :
>>  Incorrect number of arguments (2), expecting 1 for R_isMethodsDispatchOn
>>
>> The Java pseudo code would be like:
>>
>> public class Test{
>>  public static void main(String[] args){
>>    ...
>>    objA.do;
>>    objB.do;
>>    ...
>>  }
>> }
>>
>> Each do method actually calls R to do the job. I already know R is single-treaded so I implemented end method in Rengine class to shutdown R in each method.
> 
> You cannot shutdown R short of closing the process and thus JVM, so that is not an option. In fact NOT using end will likely solve your problem - simply used one, shared instance of the REngine.
> 
> 
>> I thought this won't cause multi-thread problems in this case because I terminate/destroy each R thread before I call another one. But, it seems that it's still considered as 2 threads. Did I miss something? or probably, I have to set-up JRI server for my project? or other recommendations for my purpose?
>>
> 
> Simply use one instance of REngine continuously - that's the only approach possible with JRI (note that the R access is synchronized so you can use the instance from different threads). If you need multiple instances, you can use Rserve - it uses the same REngine API but allows you to have arbitrarily many parallel instances.
> 
> BTW: please use stats-rosuda-devel mailing list of questions related to rJava, JRI or Rserve. It's also worth scanning the archives as those issues have been raised before.
> 
> Cheers,
> Simon
> 
> 
> 
>> R version: 2.11.1
>> rJava version: 0.8-4
>> OS: Arch Linux
>>
>> Best,
>> Keith
>>
Thanks for the quick reply. It clears my confusion of using JRI. Now I 
knew the stats-rosuda-devel mailing list, and I'll raise the related 
questions/problems there next time.

Cheers,
Keith