Comparison

In order to scale your results, ESBench supports compare results with a baseline or previous runs.

Baseline

If you want to know the effect of a variable on the results, you can mark one of the values of that variable as the baseline.

import { defineSuite } from "esbench";

export default defineSuite({
	params: {
		length: [0, 100, 100_00],
	},
	baseline: {
		type: "Name",
		value: "For-index",
	},
	setup(scene) {
		const { length } = scene.params;
		const values = Array.from({ length }, (_, i) => i);

		scene.bench("For-index", () => {
			let sum = 0;
			for (let i = 0; i < length; i++) sum += values[i];
			return sum;
		});

		scene.bench("For-of", () => {
			let sum = 0;
			for (const v of values) sum += v;
			return sum;
		});

		scene.bench("Array.reduce", () => {
			// Empty array require a init value for reducing.
			return values.reduce((v, s) => s + v, 0);
		});
	},
});

If the baseline option is set, rows in the text report will be grouped and a new *.ratio column will be added to show the difference between the other use cases and the baseline case:

Change the baseline to { type: "length", value: 100 } and the report will be:

Previous Runs

ESBench can also compare the results with the previous run, This feature is enabled by default.

Run a suite twice, you'll see a *.diff column added to the table, showing the difference between the current result and the saved result:

The built-in htmlReporter also compares the differences, with the previous run plotted as a patterned bar:

This feature is accomplished by several config items. When execution is complete, rawReporter saves the result to a file. The next time it is run ESBench tries to read the file specified by the diff option, and if it exists passes it to reporters as the result of the previous run.

import { defineConfig, rawReporter, textReporter } from "esbench/host";

// This is the detault value of `reporters` and `diff`.
export default defineConfig({
	reporters: [
		// Save the results to node_modules/.esbench/result.json.
		rawReporter("node_modules/.esbench/result.json"),
        
        // Show tables in console.
		textReporter(),
	],
	// Read a results file to compare with. 
    // Set it to null to disable this feature.
	diff: "node_modules/.esbench/result.json",
});