forked from kscience/kmath
81 lines
2.2 KiB
Markdown
81 lines
2.2 KiB
Markdown
# Abstract Syntax Tree Expression Representation and Operations (`kmath-ast`)
|
|
|
|
This subproject implements the following features:
|
|
|
|
${features}
|
|
|
|
${artifact}
|
|
|
|
## 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:
|
|
|
|
```kotlin
|
|
DoubleField.mstInField { symbol("x") + 2 }.compile()
|
|
```
|
|
|
|
… leads to generation of bytecode, which can be decompiled to the following Java class:
|
|
|
|
```java
|
|
package space.kscience.kmath.asm.generated;
|
|
|
|
import java.util.Map;
|
|
import kotlin.jvm.functions.Function2;
|
|
import space.kscience.kmath.asm.internal.MapIntrinsics;
|
|
import space.kscience.kmath.expressions.Expression;
|
|
import space.kscience.kmath.expressions.Symbol;
|
|
|
|
public final class AsmCompiledExpression_45045_0 implements Expression<Double> {
|
|
private final Object[] constants;
|
|
|
|
public final Double invoke(Map<Symbol, ? extends 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:
|
|
|
|
```kotlin
|
|
DoubleField.mstInField { symbol("x") + 2 }.compile()
|
|
DoubleField.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.
|
|
|
|
```kotlin
|
|
DoubleField.mstInField { symbol("x") + 2 }.compile()
|
|
```
|
|
|
|
The code above returns expression implemented with such a JS function:
|
|
|
|
```js
|
|
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.
|