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From Phil Steitz <phil.ste...@gmail.com>
Subject Re: [nabla] INVOKEVIRTUAL not handled yet
Date Sat, 08 Oct 2011 21:42:29 GMT
On 10/8/11 2:24 PM, Luc Maisonobe wrote:
>
>
> Phil Steitz <phil.steitz@gmail.com> a écrit :
>
>> I am getting RTE with message above when I try to run the example
>> under "updating the base and differentiated objects" in the docs. 
>> Is this example supposed to work with the code in trunk?  Also, I am
> I'll look at this tomorrow, but I think for now you need to have a standalone function,
it cannot be split
> as a main function calling subfunctions. The only allowed calls are the static methods
from Math/StrictMath.
> I did not add our own FastMath, but it is trivial to do.
>
> Another limitation is that your function cannot store intermediate results as clas attributes
yet.

Thanks, Luc!  What I was trying to illustrate was partial
derivatives, which IIUC you need something like that example to do. 
The following almost works:
   
   public void testPartialDerivatives() throws Exception {
        PartialFunction function = new PartialFunction(1);
        final UnivariateDerivative derivative = new
ForwardModeAlgorithmicDifferentiator().differentiate(function);
        DifferentialPair t = DifferentialPair.newVariable(1);
        Assert.assertEquals(3, derivative.f(t).getFirstDerivative(), 0);
        Assert.assertEquals(2, derivative.f(t).getValue(), 0);
        function.setX(2);
        Assert.assertEquals(4, derivative.f(t).getFirstDerivative(), 0);
        Assert.assertEquals(3, derivative.f(t).getValue(), 0);
    }

with

public class PartialFunction implements UnivariateDifferentiable {
    private double x;
    public PartialFunction(double x) {
        this.x = x;
    }
    public void setX(double x) {
        this.x = x;
    }
    public double getX() {
        return x;
    }
    public double f(double y) {
        return x * y + y * y;
    } 
}

But I end up with java.lang.VerifyError: (class:
ExampleTest$1PartialFunction$NablaForwardModeUnivariateDerivative,
method: f signature:
(Lorg/apache/commons/nabla/core/DifferentialPair;)Lorg/apache/commons/nabla/core/DifferentialPair;)
Incompatible type for getting or setting field
    at java.lang.Class.getDeclaredConstructors0(Native Method)
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
    at java.lang.Class.getDeclaredConstructors(Class.java:1836)
    at
org.apache.commons.nabla.algorithmic.forward.ForwardModeAlgorithmicDifferentiator.differentiate(ForwardModeAlgorithmicDifferentiator.java:107)
    at ExampleTest.testPartialDerivatives(ExampleTest.java:66)
>
>
> You can look at the junit tests for what is supported.  Simple expressions, calls to
traditional functions like sin, cos, exp ...,
> Simple loops and conditionals, local automatic variables should all work (I hope ...)

Yep, I have gotten all of this to work.  Even "knows" the chain rule :)


Phil
>
>> assuming
>> s/ForwardAlgorithmicDifferentiator/ForwardModeAlgorithmicDifferentiator
>> throughout.  Correct?
> Yes, the name was changed because a distant goal will be to also support reverse mode,
which is especially
> useful when computing gradients (i.e. when one scalar function depends on many inputs
and we want all partial
> derivatives).
>
> Luc
>
>> Phil
>>
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