kmath/kmath-ast/docs/README-TEMPLATE.md

Abstract Syntax Tree Expression Representation and Operations (kmath-ast)

This subproject implements the following features:

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Dynamic expression code generation

On JVM

kmath-ast JVM module supports runtime code generation to eliminate overhead of tree traversal. Code generator builds a special implementation of Expression<T> with implemented invoke function.

For example, the following builder:

RealField.mstInField { symbol("x") + 2 }.compile()

… leads to generation of bytecode, which can be decompiled to the following Java class:

package kscience.kmath.asm.generated;

import java.util.Map;
import kotlin.jvm.functions.Function2;
import kscience.kmath.asm.internal.MapIntrinsics;
import kscience.kmath.expressions.Expression;
import kscience.kmath.expressions.Symbol;

public final class AsmCompiledExpression_45045_0 implements Expression<Double> {
    private final Object[] constants;

    public final Double invoke(Map<Symbol, Double> arguments) {
        return (Double)((Function2)this.constants[0]).invoke((Double)MapIntrinsics.getOrFail(arguments, "x"), 2);
    }

    public AsmCompiledExpression_45045_0(Object[] constants) {
        this.constants = constants;
    }
}

Example Usage

This API extends MST and MstExpression, so you may optimize as both of them:

RealField.mstInField { symbol("x") + 2 }.compile()
RealField.expression("x+2".parseMath())

Known issues

• The same classes may be generated and loaded twice, so it is recommended to cache compiled expressions to avoid class loading overhead.
• This API is not supported by non-dynamic JVM implementations (like TeaVM and GraalVM) because of using class loaders.

On JS

A similar feature is also available on JS.

RealField.mstInField { symbol("x") + 2 }.compile()

The code above returns expression implemented with such a JS function:

var executable = function (constants, arguments) {
  return constants[1](constants[0](arguments, "x"), 2);
};

Known issues

• This feature uses eval which can be unavailable in several environments.