Problem using java class inside jruby

Question

I am trying to use Java Opencl from jruby, but I am facing a problem that I cannot solve, even with a big google search.

require 'java' require 'JOCL-0.1.7.jar' platforms = org.jocl.cl_platform_id.new puts platforms.class org.jocl.CL.clGetPlatformIDs(1, platforms, nil) 

when I run this code using: jruby test.rb I get the following error when the last line is uncommented:

 #<Class:0x10191777e> TypeError: cannot convert instance of class org.jruby.java.proxies.ConcreteJavaP roxy to class [Lorg.jocl.cl_platform_id; LukeTest at test.rb:29 (root) at test.rb:4 

Just wondering if anyone has an idea on how to solve this problem?

EDIT: OK, so I think I solved the first part of this problem by making the platforms an array:

 platforms = org.jocl.cl_platform_id[1].new 

but this led to this error when adding the following two lines:

 context_properties = org.jocl.cl_context_properties.new() context_properties.addProperty(org.jocl.CL::CL_CONTEXT_PLATFORM, platforms[0]) 

 CodegenUtils.java:98:in `human': java.lang.NullPointerException from CodegenUtils.java:152:in `prettyParams' from CallableSelector.java:462:in `argumentError' from CallableSelector.java:436:in `argTypesDoNotMatch' from RubyToJavaInvoker.java:248:in `findCallableArityTwo' from InstanceMethodInvoker.java:66:in `call' from CachingCallSite.java:332:in `cacheAndCall' from CachingCallSite.java:203:in `call' from test.rb:36:in `module__0$RUBY$LukeTest' from test.rb:-1:in `module__0$RUBY$LukeTest' from test.rb:4:in `__file__' from test.rb:-1:in `load' from Ruby.java:679:in `runScript' from Ruby.java:672:in `runScript' from Ruby.java:579:in `runNormally' from Ruby.java:428:in `runFromMain' from Main.java:278:in `doRunFromMain' from Main.java:198:in `internalRun' from Main.java:164:in `run' from Main.java:148:in `run' from Main.java:128:in `main' 

for some reason, when I print the platform class [0], it is listed as NilClass !?

Answer 1

You are ignoring a very simple mistake. You write

 platforms = org.jocl.cl_platform_id.new 

but this line creates one instance of the org.jocl.cl_platform_id class. Then you pass this as the second parameter to org.jocl.CL.clGetPlatformIDs in

 org.jocl.CL.clGetPlatformIDs(1, platforms, nil) 

and this does not work because the second argument to the method requires an (empty) array of org.jocl.cl_platform_id objects.

What the error says: "I have something proxies for the Java object, and I cannot turn it into an array of org.jocl.cl_platform_id objects, as you ask me about it.

If you just say

 platforms = [] 

and pass it on, it may just work :).