Refactor solver loops: index loops, remove itors, remove Map usage

Speedup reasons

Author: babaissarkar

src/main/java/com/babai/ssplot/cli/SSPlotCLI.java

@@ -25,7 +25,6 @@
 import java.io.IOException;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.util.Map;
 import java.util.Scanner;
 
 import javax.imageio.ImageIO;
@@ -73,7 +72,7 @@ private static void startREPL() {
 				if (line.equalsIgnoreCase("exit")) {
 					break;
 				} else {
-					System.out.println(parser.evaluate(line, Map.of()));
+					System.out.println(parser.evaluate(line));
 				}
 			}
 		} catch (Exception e) {

src/main/java/com/babai/ssplot/math/system/core/EquationSystem.java

@@ -24,7 +24,6 @@
 package com.babai.ssplot.math.system.core;
 
 import java.util.Arrays;
-import java.util.Iterator;
 
 /**
  * Class that holds data for system of equations.
@@ -43,9 +42,18 @@ public record EquationSystem (
 	public static final double DEFAULT_H = 0.05; /* Default stepsize for RK4                */
 	public static final Range DEFAULT_RANGE =
 			new Range(-10, 10, 0.1);             /* Default range for the variables x, y, z */
+	
 	public int numberOfEqns() {
 		return (int) Arrays.stream(eqns).filter(eqn -> !eqn.isEmpty() && !eqn.isBlank()).count();
 	}
+	
+	public String eqn(int i) {
+		return eqns[i];
+	}
+	
+	public Range range(int i) {
+		return ranges[i];
+	}
 
 	@Override
 	public String toString() {
@@ -154,7 +162,7 @@ public EquationSystem build() {
 	}
 
 	/** Small record for storing range info for each independent variable */
-	public record Range(double start, double end, double step) implements Iterable<Double> {
+	public record Range(double start, double end, double step) {
 
 		public Range(double start, double end) {
 			this(start, end, start < end ? 1 : -1);
@@ -163,42 +171,20 @@ public Range(double start, double end) {
 		public Range(double end) {
 			this(0, end, end > 0 ? 1 : -1);
 		}
-
-		@Override
-		public Iterator<Double> iterator() {
-			return new Iterator<Double>() {
-				Double current = start;
-
-				@Override
-				public boolean hasNext() {
-					if (step == 0) throw new IllegalArgumentException("Step cannot be zero!");
-					return step > 0 ? current < end : current > end;
-				}
-
-				@Override
-				public Double next() {
-					current += step;
-					return current;
-				}
-
-			};
+		
+		public double at(int i) {
+			return start + step * i;
 		}
 
 		/** NOTE: does not include endpoint */
 		public int count() {
-			return (int) Math.floor((end - start) / step);
+			if (step == 0) throw new IllegalArgumentException("Step cannot be zero!");
+			return (int) Math.round((end - start) / step);
 		}
 
 		public double[] toArray() {
 			return new double[] { start(), end(), step() };
 		}
-
-
-		public void printAllPoints() {
-			for (double d : this) {
-				System.out.println(d);
-			}
-		}
 	}
 
 }

src/main/java/com/babai/ssplot/math/system/parser/Parser.java

@@ -23,11 +23,11 @@
 
 package com.babai.ssplot.math.system.parser;
 
-import java.util.Map;
-
 public interface Parser {
-	// Evaluate an expression using this parser
-	double evaluate(String expression, Map<String, Double> variables);
+	public void setVariables(String... variables);
+	
+	/** Evaluate an expression using this parser */
+	public double evaluate(String expression, double... values);
 
 	public String getName();
 }

src/main/java/com/babai/ssplot/math/system/parser/ScriptParser.java

@@ -23,8 +23,6 @@
 
 package com.babai.ssplot.math.system.parser;
 
-import java.util.Map;
-
 import javax.script.ScriptEngine;
 import javax.script.ScriptException;
 
@@ -33,19 +31,28 @@
 public class ScriptParser implements Parser {
 	private String name;
 	private ScriptEngine engine;
+	private String[] varNames;
+	
+	@Override
+	public void setVariables(String... varNames) {
+		this.varNames = varNames;
+	}
 
 	public ScriptParser(String name, ScriptEngine engine) {
 		this.name = name;
 		this.engine = engine;
 	}
 
 	@Override
-	public double evaluate(String expression, Map<String, Double> variables) {
+	public double evaluate(String expression, double... variables) {
 		if (expression.isEmpty()) {
 			return 0;
 		}
 
-		variables.forEach((var, val) -> engine.put(var, val));
+		for (int i = 0; varNames != null && i < varNames.length; i++) {
+			engine.put(varNames[i], variables[i]);
+		}
+		
 		try {
 			engine.eval("answer = " + expression);
 			return (double) engine.get("answer");

src/main/java/com/babai/ssplot/math/system/parser/internal/tree/TreeNode.java

@@ -23,16 +23,20 @@
 
 package com.babai.ssplot.math.system.parser.internal.tree;
 
-import java.util.Map;
-import java.util.Vector;
+import java.util.ArrayList;
 
 public class TreeNode {
 	private TreeOperator nodeOp = null;
-	private Vector<TreeNode> nodes = new Vector<TreeNode>();
+	private ArrayList<TreeNode> nodes = new ArrayList<>();
+	private String[] varNames = new String[0];
 
 	public TreeNode(TreeOperator op) {
 		this.nodeOp = op;
 	}
+	
+	public void setVarNames(String... varNames) {
+		this.varNames = varNames;
+	}
 
 	/** 
 	 * Calculates the value of this node by
@@ -48,8 +52,11 @@ public double getValue() {
 		return res;
 	}
 
-	public double evalAt(Map<String, Double> variables) {
-		variables.forEach((var, val) -> scanVariables(var, val));
+	public double evalAt(double... values) {
+		// TODO check values len >= varName length
+		for (int varIdx = 0; varNames != null && varIdx < varNames.length; varIdx++) {
+			scanVariables(varNames[varIdx], values[varIdx]);
+		}
 		return getValue();
 	}
 
@@ -84,10 +91,10 @@ public void addChild(TreeNode node) {
 	}
 
 	public void removeChilds() {
-		nodes.removeAllElements();
+		nodes.clear();
 	}
 
-	public Vector<TreeNode> getChilds() {
+	public ArrayList<TreeNode> getChilds() {
 		return nodes;
 	}
 

src/main/java/com/babai/ssplot/math/system/parser/internal/tree/TreeParser.java

@@ -29,6 +29,8 @@
 
 public class TreeParser implements Parser {
 	private static final String NAME = "Internal";
+	private String[] varNames;
+	
 	private static final Map<String, TreeNode> exprCache = new LinkedHashMap<>(16, 0.75f, true) {
 		private static final int MAX_CACHE_ENTRIES = 100;
 		@Override
@@ -37,30 +39,38 @@ protected boolean removeEldestEntry(Map.Entry<String, TreeNode> eldest) {
 		}
 	};
 
+	public static String internalParserName() {
+		return NAME;
+	}
+	
 	@Override
-	public double evaluate(String expression, Map<String, Double> variables) {		
+	public double evaluate(String expression, double... vals) {
 		// get the cached TreeNode or parse it if missing
 		TreeNode tree = exprCache.computeIfAbsent(expression, this::parse);
 
 		// evaluate the cached AST with the provided variables
-		return tree.evalAt(variables);
+		return tree.evalAt(vals);
 	}
 
 	@Override
 	public String getName() {
 		return internalParserName();
 	}
-	
-	public static String internalParserName() {
-		return NAME;
-	}
 
 	public TreeNode parse(String token) {
+		TreeNode exprNode; 
 		try {
-			return SSMathParser.parseString(token);
+			exprNode = SSMathParser.parseString(token);
 		} catch(Exception e) {
-			return new TreeNode(new Constant(0.0));
+			exprNode = new TreeNode(new Constant(0.0));
 		}
+		exprNode.setVarNames(varNames);
+		return exprNode;
+	}
+
+	@Override
+	public void setVariables(String... varNames) {
+		this.varNames = varNames;
 	}
 }