July 13, 2026
Plot twist: the useless if wins
Quadrupling code performance with a "useless" if
A tiny “if” made code 4x faster — and commenters are losing it
TLDR: A programmer sped up code by adding an “if” that looks unnecessary but helps the computer guess the usual outcome and move faster. Commenters were stunned, with some calling it brilliant and others joking that everything they were taught about avoiding branches just got flipped upside down.
A programmer casually dropped what sounds like a tech prank — adding a seemingly pointless little “if” made part of their code run about four times faster — and the comment section reacted like someone had broken the laws of computing on live TV. The basic idea is surprisingly simple: instead of always updating a value, the code first checks whether the value actually changes. That tiny pause gives the processor a chance to guess the common case and speed through the boring parts, only fixing things when needed. In plain English: a fake-looking detour somehow becomes the fast lane.
The community was equal parts impressed, delighted, and slightly shaken. One camp was basically applauding from the rafters: “Brilliant!” and “really surprising” set the tone, with readers saying they’d never thought a no-op check — a check that often does nothing — could actually unlock more speed. Another mini-drama bubbled up around tooling: if this trick works, why don’t compilers have a clean way to express it? One commenter practically begged for a friendlier built-in hint instead of what they saw as an obscure source-code hack.
And then came the funniest plot twist: many readers have spent years hearing “branches are bad, avoid them”, only to watch this story say, actually, sometimes a branch is the hero. That contradiction became the thread’s main soap opera. The vibe was half masterclass, half support group for programmers realizing the machine is weirder than they thought.
Key Points
- •The article presents a compressor optimization problem framed as shortest-path computation on a grid, with `next_j` storing the best next cell for each position.
- •The first SIMD-heavy loop that computes `next_j` is described as already optimized and not the main focus of the post.
- •The second loop, which repeatedly performs `j = next_j[i][j]`, is limited by inter-iteration dependency on `j` and thus by memory-access latency.
- •The author proposes adding a conditional update so that when `next_j[i][j]` usually equals `j`, CPU branch prediction can speculatively break the dependency chain in the common case.
- •The article notes that this optimization conflicts with compiler behavior because the `if` appears redundant and may be removed by optimization passes.