1986183 - Modified Codepen demo at https://codepen.io/Valgo/pen/jOrqjOM?editors=0010 is slower in Firefox, spending time in filter

Status: NEW

(Core :: JavaScript Engine, task, P3)

Description

[Mayank Bansal]

Open attached html (unmodified demo at https://codepen.io/Valgo/pen/jOrqjOM?editors=0010)

firefox: https://share.firefox.dev/3HOLvy4 (34s) / https://share.firefox.dev/3JDsmQd (74s)
Chrome: https://share.firefox.dev/46gyh6w (17s)

There is some variability in the demo, so timings will change in each run.

Comment 1

[Mayank Bansal]

Attachment: index.html

Comment 2

[Iain Ireland [:iain]]

The profile shows that V8 is spending a higher fraction of its time sorting. I'm pretty sure their sorting is at least as fast as ours, so what this actually means is that we're significantly slower elsewhere, in particular in the calls to filter in collapseOne:

const collapseOne = grid => {
  const lowestEntropy = grid.filter(cell => !cell.collapsed).sort((a, b) => a.entropy - b.entropy)[0].entropy;
  const cells = grid.filter(cell => cell.entropy <= lowestEntropy && !cell.collapsed);
  
  const cell = cells[Math.floor(Math.random() * cells.length)];
  
  cell.collapsed = true;
  const collapsedState = pickState(cell);
  cell.states = [collapsedState];
  propogate(cell);
  
  return grid.filter(cell => cell.states.length === 0).length === 0;
};

(Note that this code isn't written particularly efficiently.)