Skip to main content

How to execute a function in the package from java?


I use Wolfram Workbench 2.0. I can get a KernelLink object and evaluate some simple expressions like "2+2". But I don't know how to export a package and execute any functions from Java code. Please, show me any example.



Answer



Preamble


In fact, the relevant example can be found in the documentation, here, in the "Sample program" section. To make this useful also for folks who don't have experience with Java development in WorkBench, I will illustrate how this can be done from within Mathematica, by using the interactive Java reloader from this post. You will have to figure out how to run this from within WorkBench, but this should not be really hard.


Illustration from within Mathematica


Sample code


I will construct a sample class which loads the CompiledFunctionTools` package and prints to the Java console the result of CompilePrint function applied to some sample Compile-d function, such as e.g. Compile[{x}, x + Sin[x]]. This is pretty much an adaptation of the example from JLink Help, linked above.


samplecode = 
"

import com.wolfram.jlink.*;

public class SampleProgram {
public static void main(String[] argv) {
KernelLink ml = null;
try {
ml = MathLinkFactory.createKernelLink(argv);
} catch (MathLinkException e) {
System.out.println(\"Fatal error opening link: \"
+ e.getMessage());

return;
}
try {
// Get rid of the initial InputNamePacket the kernel will send
// when it is launched.
ml.discardAnswer();

ml.evaluate(\"Needs[\\\"CompiledFunctionTools`\\\"]\");
ml.discardAnswer();


String strResult =
ml.evaluateToOutputForm(
\"CompilePrint[Compile[{x},x+Sin[x]]]\", 0);
System.out.println(
\"Instructions for function Compile[{x},x+Sin[x]]: \"
+ strResult);

ml.putFunction(\"EvaluatePacket\", 1);
ml.putFunction(\"CompilePrint\", 1);
ml.putFunction(\"Compile\",2);

ml.putFunction(\"List\",1);
ml.putSymbol(\"x\");
ml.putFunction(\"Plus\",2);
ml.putSymbol(\"x\");
ml.putFunction(\"Sin\",1);
ml.putSymbol(\"x\");
ml.endPacket();
ml.waitForAnswer();
strResult = ml.getString();
System.out.println(

\"Now conbining function call from pieces: \" + strResult);

} catch (MathLinkException e) {
System.out.println(\"MathLinkException occurred: \"
+ e.getMessage());
} finally {
ml.close();
}
}
}";


Load Java reloader


Now, you have to either copy and paste the code for the Java reloader from the link above, and run it in Front-End, or put that code in a package, place it where Mathematica can find it (e.g. FileNameJoin[{$UserBaseDirectory,"Applications"}], and call Needs["SimpleJavaReloader`"].


Using Java reloader


First, we will have to add the jlink.jar to Java classpath for Java compiler. Here is the standard location of it:


jlinkpath =  FileNameJoin[{$InstallationDirectory, "SystemFiles", "Links", 
"JLink", "JLink.jar"}]

Let us check that the files exists:


FileExistsQ[jlinkpath]



True

We are now ready to compile it:


JCompileLoad[samplecode,{jlinkpath}]


 JavaClass[SampleProgram,<>]


The class has been (hopefully) compiled and loaded by now. To see the output it produces, we can enable the Java console:


ShowJavaConsole[]

Now we make a call:


SampleProgram`main[{"-linkmode", "launch", "-linkname", 
"c:\\program files\\wolfram research\\mathematica\\8.0\\mathkernel.exe"}]

You will have to adjust the path to the mathkernel executable for your machine (I assume you are on Windows. For other platforms, the mentioned section of JLink Help lists the right commands to launch the kernel).


We now call the Java console again:


ShowJavaConsole[]


Here is the screenshot of the Java console on my machine after that:


enter image description here


WorkBench


While I did not try using WorkBench with this, this should be even simpler:



  • Create a Java project in WB

  • Create a source file for your class

  • Add jlink.jar to the set of libraries used in the project (I assume you know how to do that)

  • You will have to run the math kernel from the Java process, perhaps by calling the Process class, or by any other means.



Comments

Popular posts from this blog

mathematical optimization - Minimizing using indices, error: Part::pkspec1: The expression cannot be used as a part specification

I want to use Minimize where the variables to minimize are indices pointing into an array. Here a MWE that hopefully shows what my problem is. vars = u@# & /@ Range[3]; cons = Flatten@ { Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; Minimize[{Total@((vec1[[#]] - vec2[[u[#]]])^2 & /@ Range[1, 3]), cons}, vars, Integers] The error I get: Part::pkspec1: The expression u[1] cannot be used as a part specification. >> Answer Ok, it seems that one can get around Mathematica trying to evaluate vec2[[u[1]]] too early by using the function Indexed[vec2,u[1]] . The working MWE would then look like the following: vars = u@# & /@ Range[3]; cons = Flatten@{ Table[(u[j] != #) & /@ vars[[j + 1 ;; -1]], {j, 1, 3 - 1}], 1 vec1 = {1, 2, 3}; vec2 = {1, 2, 3}; NMinimize[ {Total@((vec1[[#]] - Indexed[vec2, u[#]])^2 & /@ R...

functions - Get leading series expansion term?

Given a function f[x] , I would like to have a function leadingSeries that returns just the leading term in the series around x=0 . For example: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x)] x and leadingSeries[(1/x + 2 + (1 - 1/x^3)/4)/(4 + x)] -(1/(16 x^3)) Is there such a function in Mathematica? Or maybe one can implement it efficiently? EDIT I finally went with the following implementation, based on Carl Woll 's answer: lds[ex_,x_]:=( (ex/.x->(x+O[x]^2))/.SeriesData[U_,Z_,L_List,Mi_,Ma_,De_]:>SeriesData[U,Z,{L[[1]]},Mi,Mi+1,De]//Quiet//Normal) The advantage is, that this one also properly works with functions whose leading term is a constant: lds[Exp[x],x] 1 Answer Update 1 Updated to eliminate SeriesData and to not return additional terms Perhaps you could use: leadingSeries[expr_, x_] := Normal[expr /. x->(x+O[x]^2) /. a_List :> Take[a, 1]] Then for your examples: leadingSeries[(1/x + 2)/(4 + 1/x^2 + x), x] leadingSeries[Exp[x], x] leadingSeries[(1/x + 2 + (1 - 1/x...

What is and isn't a valid variable specification for Manipulate?

I have an expression whose terms have arguments (representing subscripts), like this: myExpr = A[0] + V[1,T] I would like to put it inside a Manipulate to see its value as I move around the parameters. (The goal is eventually to plot it wrt one of the variables inside.) However, Mathematica complains when I set V[1,T] as a manipulated variable: Manipulate[Evaluate[myExpr], {A[0], 0, 1}, {V[1, T], 0, 1}] (*Manipulate::vsform: Manipulate argument {V[1,T],0,1} does not have the correct form for a variable specification. >> *) As a workaround, if I get rid of the symbol T inside the argument, it works fine: Manipulate[ Evaluate[myExpr /. T -> 15], {A[0], 0, 1}, {V[1, 15], 0, 1}] Why this behavior? Can anyone point me to the documentation that says what counts as a valid variable? And is there a way to get Manpiulate to accept an expression with a symbolic argument as a variable? Investigations I've done so far: I tried using variableQ from this answer , but it says V[1...