com.github.cgdon.jexpr.benchmark.Benchmark Maven / Gradle / Ivy

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// Run benchmarks from the command line.

package com.github.cgdon.jexpr.benchmark;

import com.github.cgdon.jexpr.core.Parser;
import com.github.cgdon.jexpr.core.expr.Variable;
import com.github.cgdon.jexpr.core.Expr;
import com.github.cgdon.jexpr.core.SyntaxException;

/**
 * Time evaluating many expressions over many values.
 */
public class Benchmark {
  public static void main(String[] args) {
    double parse_product = 1.0;
    double run_product = 1.0;
    for (int i = 0; i < args.length; ++i) {
      long parsetime = timeParse(args[i]);
      long runtime = timeRun(args[i]);
      System.out.println("" + msec(parsetime) + " ms(parse) "
          + msec(runtime) + " ms(run): "
          + args[i]);
      parse_product *= parsetime;
      run_product *= runtime;
    }
    if (0 < args.length) {
      double run_geomean = Math.pow(run_product, 1.0 / args.length);
      double parse_geomean = Math.pow(parse_product, 1.0 / args.length);
      System.out.println("" + msec(parse_geomean) + " ms(parse) "
          + msec(run_geomean) + " ms(run): (geometric mean)");
    }
  }

  static long msec(double nsec) {
    return (long) Math.rint(nsec * 1e-6);
  }

  static final int nruns = 1000000;

  static long timeRun(String expression) {
    Variable x = Variable.make("x");
    Expr expr = parse(expression);

    double low = 0.0;
    double high = 4.0;
    double step = (high - low) / nruns;

    long start = System.nanoTime();
    for (double xval = low; xval <= high; xval += step) {
      x.setValue(xval);
      expr.value();
    }
    return System.nanoTime() - start;
  }

  static final int nparses = 1000;

  static long timeParse(String expression) {
    long start = System.nanoTime();
    for (int i = 0; i < nparses; ++i)
      parse(expression);
    return System.nanoTime() - start;
  }

  static Expr parse(String expression) {
    try {
      return Parser.parse(expression);
    } catch (SyntaxException e) {
      System.err.println(e.explain());
      throw new Error(e);
    }
  }
}