Node Performance Measurement

I was working on optimising a javascript maths function and wanted to compare the performance of different versions of the code. Initially I had some difficulty because I was approaching it incorrectly so I wanted to make a note for future reference.

First mistake – only using a small number of runs. I was comparing the two different functions with a very small iteration amount. This was leading to weird results where each iteration would get faster even though it was actually the same code running. I think this was related to some compiler optimisation or something. Anyway, after reading JavaScript Compiler Optimization Techniques, I changed to a very large number of runs. This made the results much more consistent.

Second mistake – using perf_hooks incorrectly. From the same blog I also found out the nice way to use perf_hooks to measure the performance:`

import { performance, PerformanceObserver } from 'perf_hooks';

let iterations = 1_000_000;

performance.mark('start');
while (iterations--) {
    StableMath._calcOutGivenIn(
        poolPairDataBigInt.amp,
        poolPairDataBigInt.balances,
        poolPairDataBigInt.tokenIndexIn,
        poolPairDataBigInt.tokenIndexOut,
        amt,
        poolPairDataBigInt.fee
    );
}
performance.mark('end');

iterations = 1_000_000;

performance.mark('startSecond');
const invariant = StableMath._calculateInvariant(
    poolPairDataBigInt.amp,
    poolPairDataBigInt.balances,
    true
);
while (iterations--) {
    StableMath._calcOutGivenInNoInv(
        poolPairDataBigInt.amp,
        poolPairDataBigInt.balances,
        poolPairDataBigInt.tokenIndexIn,
        poolPairDataBigInt.tokenIndexOut,
        amt,
        poolPairDataBigInt.fee,
        invariant
    );
}
performance.mark('endSecond');

const obs = new PerformanceObserver((list, observer) => {
    console.log(list.getEntries()); // [0]);
    performance.clearMarks();
    observer.disconnect();
});
obs.observe({ entryTypes: ['measure'] });

performance.measure('NoOptimisation', 'start', 'end');
performance.measure('WithOptimisation', 'startSecond', 'endSecond');

Which results in an output like:

[
  PerformanceMeasure {
    name: 'NoOptimisation',
    entryType: 'measure',
    startTime: 2369.287365913391,
    duration: 35891.85489702225,
    detail: null
  },
  PerformanceMeasure {
    name: 'WithOptimisation',
    entryType: 'measure',
    startTime: 38261.19673395157,
    duration: 18529.005373954773,
    detail: null
  }
]

As well as having a nice output it also shows my optimisation worked pretty nicely!

Photo by Saffu on Unsplash