mxparser performance for single expression evaluated multiple times

Question

I have a scenario where I need to evaluate one expression 1 million times, but on each iteration the only things that do change are the argument values:

var x1 = new Argument("X1", double.NaN);
var x2 = new Argument("X2", double.NaN);
var x3 = new Argument("X3", double.NaN);
Expression expression = new Expression(
    "coalesce(X1, 0) + coalesce(X2, 0) + coalesce(X3, 0)",
    x1, x2, x3);
var calculateElapsed = new List<double>();
var getComputingTime = new List<double>();

var s1 = mXparser.currentTimeMillis();
foreach (var i in Enumerable.Range(1, 1000000))
{
    x1.setArgumentValue(i % 5 == 0 ? double.NaN : i % 5);
    x2.setArgumentValue(i % 7 == 0 ? double.NaN : i % 7);
    x3.setArgumentValue(i % 3 == 0 ? double.NaN : i % 3);

    var s2 = mXparser.currentTimeMillis();
    expression.calculate();
    var e2 = mXparser.currentTimeMillis();
    calculateElapsed.Add(e2 - s2);
    getComputingTime.Add(expression.getComputingTime());
}
var e1 = mXparser.currentTimeMillis();

Based on the run's benchmark statistics, getComputingTime() is measuring significantly smaller values than getCurrentMillis() indicating some sort of pre-evaluation overheads.

-----------------------------------------------------------------------------------
|                  | Avg(ms)  | Median(ms) | Min(ms)  | Max(ms)    | Total(ms)    |
-----------------------------------------------------------------------------------
| getComputingTime | 0.000004 | 0.000000   | 0.000000 | 0.121000   | 4.206000     |
-----------------------------------------------------------------------------------
| calculate()      | 0.004300 | 0.000000   | 0.000000 | 131.000000 | 4,300.000000 |
-----------------------------------------------------------------------------------

I am not sure what overhead this should be, since I would assume the expression does not change so we only need to parse once.

Is there some sort of configuration or pattern that would allow me to reduce this overhead cost of calculate() when the expression is the same and only the arguments values are varying?

score 0 · Accepted Answer · answered Sep 10 '20 at 18:12

Max most likely will be the first call of calculate(), where all pre-compilation is done. You are just changing argument values, so mXparser calculates it really fast after the first call of calculate() method. Remove from the stats first iteration and then rerun your test.

mxparser performance for single expression evaluated multiple times

1 Answers1