On 10/8/11 2:24 PM, Luc Maisonobe wrote:
>
>
> Phil Steitz <phil.ste...@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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