Re: [igraph] Igraph with JNI

[Gang Su]

Tamas,

I took a look at some of the c source code and understand what you  
meant. Actually I have been playing around jna: Java Native Access:

https://jna.dev.java.net/

It provides a much nicer way to connect C and Java. There's a tool called

http://code.google.com/p/jnaerator/

That can help auto generating interfaces to map c functions.
I just began to look at these things yesterday, but I have already  
successfully connecting c and java over my experiments. I tried a  
little bit on igraph, the major problem is custom data structrue  
mapping.

The following data structure can't be mapped directly:
igragh_vector_t
igraph_vector_bool_t
igraph_array3_t
igraph_matrix_t

The jna can only define java jna "pointer" association to these data  
structures. Then the java programmer need to know exactly how these  
data structures are formed, and extend the pointer class to add  
functions to find, add, set, retrive data. It can be a little bit  
complicated.

There are several work arounds:
1. To write a wrapper function to convert primitive java types into  
igraph types. For example, when a java int[] array is passed, convert  
to igraph_vector_t first, after computation, assign the values back  
into int[] array, this will automatically pass the values back to java  
as the java int[] array were passed into c by reference.

2. Need to know exactly how those data types are defined. Need header  
files for those data types. If I know how those data types are defined  
then it's possible to write java interfaces. I couldn't find the  
definition of these data types header in the include folder... could  
you tell me where they are?

3. Re-implement the data types in java. This also require me to know  
the structure of these datatypes and how pointers work on these data  
types. Take a look at jna pointer api:
https://jna.dev.java.net/nonav/javadoc/com/sun/jna/Pointer.html

This is what i have got so far. I am going to try some small programs  
to connect java to igraph. I will keep you updated.


Gang











Quoting Tamas Nepusz <address@hidden>:

> Hi Gang,
>
> > Also if you could provide me with some of your proof-of-concept  
> > code that will be great.
> I will clean up my code soon and commit it to the igraph Launchpad  
> repository so you can take a look at it. The conversion between C  
> and Java is not completely trivial as we have some C functions that  
> are able to return multiple values via input pointers, and this  
> cannot be reproduced easily in Java (e.g., if a community detection  
> routine uses a pointer to a C double to return the modularity of the  
> obtained partition if the pointer is not null, this cannot be  
> translated directly to Java as there's no such thing as a pointer in  
> Java).
> Anyway, if you take a look at the igraph source tree, we have an  
> interface generator written in Python that is responsible for  
> producing a large amount of glue code between R and C. I started  
> adapting the interface generator to be able to do the same for Java  
> and C, and this is already used in my experiments with a Java  
> interface for igraph. This means that you will need a working Python  
> interpreter to use my code.
>
> --
> Tamas



Gang Su

PhD student
Bioinformatics training track
Program in Biomedical Sciences
University of Michigan, Ann Arbor
MI, 48105, U.S.A.