forked from kscience/kmath
117 lines
3.7 KiB
Markdown
117 lines
3.7 KiB
Markdown
# Module kmath-ast
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Abstract syntax tree expression representation and related optimizations.
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${features}
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${artifact}
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## Dynamic expression code generation
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### On JVM
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`kmath-ast` JVM module supports runtime code generation to eliminate overhead of tree traversal. Code generator builds
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a special implementation of `Expression<T>` with implemented `invoke` function.
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For example, the following builder:
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```kotlin
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DoubleField.mstInField { symbol("x") + 2 }.compile()
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```
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… leads to generation of bytecode, which can be decompiled to the following Java class:
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```java
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package space.kscience.kmath.asm.generated;
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import java.util.Map;
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import kotlin.jvm.functions.Function2;
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import space.kscience.kmath.asm.internal.MapIntrinsics;
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import space.kscience.kmath.expressions.Expression;
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import space.kscience.kmath.expressions.Symbol;
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public final class AsmCompiledExpression_45045_0 implements Expression<Double> {
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private final Object[] constants;
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public final Double invoke(Map<Symbol, ? extends Double> arguments) {
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return (Double)((Function2)this.constants[0]).invoke((Double)MapIntrinsics.getOrFail(arguments, "x"), 2);
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}
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public AsmCompiledExpression_45045_0(Object[] constants) {
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this.constants = constants;
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}
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}
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```
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### Example Usage
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This API extends MST and MstExpression, so you may optimize as both of them:
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```kotlin
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DoubleField.mstInField { symbol("x") + 2 }.compile()
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DoubleField.expression("x+2".parseMath())
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```
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#### Known issues
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- The same classes may be generated and loaded twice, so it is recommended to cache compiled expressions to avoid
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class loading overhead.
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- This API is not supported by non-dynamic JVM implementations (like TeaVM and GraalVM) because of using class loaders.
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### On JS
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A similar feature is also available on JS.
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```kotlin
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DoubleField.mstInField { symbol("x") + 2 }.compile()
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```
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The code above returns expression implemented with such a JS function:
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```js
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var executable = function (constants, arguments) {
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return constants[1](constants[0](arguments, "x"), 2);
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};
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```
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#### Known issues
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- This feature uses `eval` which can be unavailable in several environments.
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## Rendering expressions
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kmath-ast also includes an extensible engine to display expressions in LaTeX or MathML syntax.
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Example usage:
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```kotlin
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import space.kscience.kmath.ast.*
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import space.kscience.kmath.ast.rendering.*
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public fun main() {
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val mst = "exp(sqrt(x))-asin(2*x)/(2e10+x^3)/(-12)".parseMath()
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val syntax = FeaturedMathRendererWithPostProcess.Default.render(mst)
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val latex = LatexSyntaxRenderer.renderWithStringBuilder(syntax)
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println("LaTeX:")
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println(latex)
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println()
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val mathML = MathMLSyntaxRenderer.renderWithStringBuilder(syntax)
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println("MathML:")
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println(mathML)
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}
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```
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Result LaTeX:
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%7D%7B2%5Ctimes10%5E%7B10%7D%2Bx%5E%7B3%7D%7D%7D%7B-12%7D)
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Result MathML (embedding MathML is not allowed by GitHub Markdown):
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```html
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<mrow><msup><mrow><mi>e</mi></mrow><mrow><msqrt><mi>x</mi></msqrt></mrow></msup><mo>-</mo><mfrac><mrow><mfrac><mrow><msup><mrow><mo>sin</mo></mrow><mrow><mo>-</mo><mn>1</mn></mrow></msup><mspace width="0.167em"></mspace><mfenced open="(" close=")" separators=""><mn>2</mn><mspace width="0.167em"></mspace><mi>x</mi></mfenced></mrow><mrow><mn>2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>10</mn></mrow></msup><mo>+</mo><msup><mrow><mi>x</mi></mrow><mrow><mn>3</mn></mrow></msup></mrow></mfrac></mrow><mrow><mo>-</mo><mn>12</mn></mrow></mfrac></mrow>
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```
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It is also possible to create custom algorithms of render, and even add support of other markup languages
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(see API reference).
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