Merge pull request #111 from CommanderTvis/adv-expr-readme

Update readme, accident documentation-related refactor

kmath-ast/README.md

@@ -1,4 +1,61 @@
-# AST based expression representation and operations
+# AST-based expression representation and operations (`kmath-ast`)
 
-## Dynamic expression code generation
-Contributed by [Iaroslav Postovalov](https://github.com/CommanderTvis).
+This subproject implements the following features:
+
+- Expression Language and its parser.
+- MST as expression language's syntax intermediate representation.
+- Type-safe builder of MST.
+- Evaluating expressions by traversing MST.
+
+## Dynamic expression code generation with OW2 ASM
+
+`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
+    RealField.mstInField { symbol("x") + 2 }.compile()
+``` 
+
+… leads to generation of bytecode, which can be decompiled to the following Java class: 
+
+```java
+package scientifik.kmath.asm.generated;
+
+import java.util.Map;
+import scientifik.kmath.asm.internal.AsmCompiledExpression;
+import scientifik.kmath.operations.Algebra;
+import scientifik.kmath.operations.RealField;
+
+// The class's name is build with MST's hash-code and collision fixing number. 
+public final class AsmCompiledExpression_45045_0 extends AsmCompiledExpression<Double> {
+    // Plain constructor
+    public AsmCompiledExpression_45045_0(Algebra algebra, Object[] constants) {
+        super(algebra, constants);
+    }
+
+    // The actual dynamic code: 
+    public final Double invoke(Map<String, ? extends Double> arguments) {
+        return (Double)((RealField)super.algebra).add((Double)arguments.get("x"), (Double)2.0D);
+    }
+}
+```
+
+### Example Usage
+
+This API is an extension to MST and MSTExpression APIs. You may optimize both MST and MSTExpression: 
+
+```kotlin
+RealField.mstInField { symbol("x") + 2 }.compile()
+RealField.expression("2+2".parseMath())
+```
+
+### Known issues
+
+- Using numeric algebras causes boxing and calling bridge methods. 
+- 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.
+
+Contributed by [Iaroslav Postovalov](https://github.com/CommanderTvis).

kmath-ast/src/jvmMain/kotlin/scientifik/kmath/asm/asm.kt

@@ -4,11 +4,11 @@ import scientifik.kmath.asm.internal.AsmBuilder
 import scientifik.kmath.asm.internal.buildName
 import scientifik.kmath.asm.internal.hasSpecific
 import scientifik.kmath.asm.internal.tryInvokeSpecific
-import scientifik.kmath.ast.MST
-import scientifik.kmath.ast.MSTExpression
+import scientifik.kmath.ast.*
 import scientifik.kmath.expressions.Expression
 import scientifik.kmath.operations.Algebra
 import scientifik.kmath.operations.NumericAlgebra
+import scientifik.kmath.operations.RealField
 import kotlin.reflect.KClass
 
 /**
@@ -78,4 +78,8 @@ inline fun <reified T : Any> Algebra<T>.expression(mst: MST): Expression<T> = ms
 /**
  * Optimize performance of an [MSTExpression] using ASM codegen
  */
-inline fun <reified T : Any> MSTExpression<T>.compile(): Expression<T> = mst.compileWith(T::class, algebra)
+inline fun <reified T : Any> MSTExpression<T>.compile(): Expression<T> = mst.compileWith(T::class, algebra)
+
+fun main() {
+    RealField.mstInField { symbol("x") + 2 }.compile()
+}

kmath-ast/src/jvmMain/kotlin/scientifik/kmath/asm/internal/AsmBuilder.kt

@@ -8,7 +8,7 @@ import scientifik.kmath.asm.internal.AsmBuilder.ClassLoader
 import scientifik.kmath.operations.Algebra
 
 /**
- * ASM Builder is a structure that abstracts building a class that unwraps [AsmExpression] to plain Java expression.
+ * ASM Builder is a structure that abstracts building a class for unwrapping [MST] to plain Java expression.
  * This class uses [ClassLoader] for loading the generated class, then it is able to instantiate the new class.
  *
  * @param T the type generated [AsmCompiledExpression] operates.
@@ -343,7 +343,7 @@ internal class AsmBuilder<T> internal constructor(
          * Maps JVM primitive numbers boxed types to their letters of JVM signature convention.
          */
         private val SIGNATURE_LETTERS: Map<Class<out Any>, String> by lazy {
-            mapOf(
+            hashMapOf(
                 java.lang.Byte::class.java to "B",
                 java.lang.Short::class.java to "S",
                 java.lang.Integer::class.java to "I",

kmath-ast/src/jvmMain/kotlin/scientifik/kmath/asm/internal/optimization.kt

@@ -3,7 +3,13 @@ package scientifik.kmath.asm.internal
 import org.objectweb.asm.Opcodes
 import scientifik.kmath.operations.Algebra
 
-private val methodNameAdapters: Map<String, String> = mapOf("+" to "add", "*" to "multiply", "/" to "divide")
+private val methodNameAdapters: Map<String, String> by lazy {
+    hashMapOf(
+        "+" to "add",
+        "*" to "multiply",
+        "/" to "divide"
+    )
+}
 
 /**
  * Checks if the target [context] for code generation contains a method with needed [name] and [arity].
@@ -13,7 +19,7 @@ private val methodNameAdapters: Map<String, String> = mapOf("+" to "add", "*" to
 internal fun <T> hasSpecific(context: Algebra<T>, name: String, arity: Int): Boolean {
     val aName = methodNameAdapters[name] ?: name
 
-    context::class.java.methods.find { it.name == aName && it.parameters.size == arity }
+    context.javaClass.methods.find { it.name == aName && it.parameters.size == arity }
         ?: return false
 
     return true
@@ -28,7 +34,7 @@ internal fun <T> hasSpecific(context: Algebra<T>, name: String, arity: Int): Boo
 internal fun <T> AsmBuilder<T>.tryInvokeSpecific(context: Algebra<T>, name: String, arity: Int): Boolean {
     val aName = methodNameAdapters[name] ?: name
 
-    context::class.java.methods.find { it.name == aName && it.parameters.size == arity }
+    context.javaClass.methods.find { it.name == aName && it.parameters.size == arity }
         ?: return false
 
     val owner = context::class.java.name.replace('.', '/')