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
---
