Github user twilmes commented on a diff in the pull request: https://github.com/apache/tinkerpop/pull/729#discussion_r142936026 --- Diff: gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MathStep.java --- @@ -0,0 +1,171 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ + +package org.apache.tinkerpop.gremlin.process.traversal.step.map; + +import net.objecthunter.exp4j.Expression; +import net.objecthunter.exp4j.ExpressionBuilder; +import org.apache.tinkerpop.gremlin.process.traversal.Pop; +import org.apache.tinkerpop.gremlin.process.traversal.Traversal; +import org.apache.tinkerpop.gremlin.process.traversal.Traverser; +import org.apache.tinkerpop.gremlin.process.traversal.step.ByModulating; +import org.apache.tinkerpop.gremlin.process.traversal.step.PathProcessor; +import org.apache.tinkerpop.gremlin.process.traversal.step.Scoping; +import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent; +import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement; +import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalRing; +import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil; +import org.apache.tinkerpop.gremlin.structure.util.StringFactory; + +import java.util.HashSet; +import java.util.LinkedHashSet; +import java.util.List; +import java.util.Set; +import java.util.regex.Matcher; +import java.util.regex.Pattern; + +/** + * @author Marko A. Rodriguez (http://markorodriguez.com) + */ +public final class MathStep<S> extends MapStep<S, Double> implements ByModulating, TraversalParent, Scoping, PathProcessor { + + private static final String CURRENT = "_"; + private final String equation; + private final Set<String> variables; + private TraversalRing<Object, Number> traversalRing = new TraversalRing<>(); + private Set<String> keepLabels; + + public MathStep(final Traversal.Admin traversal, final String equation) { + super(traversal); + this.equation = equation; + this.variables = MathStep.getVariables(this.equation); + + } + + @Override + protected Traverser.Admin<Double> processNextStart() { + return PathProcessor.processTraverserPathLabels(super.processNextStart(), this.keepLabels); + } + + @Override + protected Double map(final Traverser.Admin<S> traverser) { + final Expression expression = new ExpressionBuilder(this.equation) --- End diff -- Yes, good point. I was trying to think of a way to do it with a `ThreadLocal` but can't think of one. I think I found a way around the threading issue that at least circumvents the repeated expression parsing. We can't get away from the extra object creation but the `Expression` constructor can take an `Expression` as input. That creates a copy with the tokens already pulled out so no parsing is needed. A golden copy of the expression could be created in the constructor and then used to seed the method-level expressions. I ran this quick little test against grateful-dead.kryo. It's a nonsensical query, but I wanted to see how much of a difference parsing made. `clockWithResult(20000){g.V().hasLabel("song").math("_ * 100 + 200 / 300").by('performances').limit(1000).toList()}` original: 0.87 ms `new Expression(expression)`: 0.38 ms
---