LANGUAGES Signal 360
Branchless Rust: Making a Filter 4x Faster by Removing an if
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Branch mispredictions stall the processor pipeline, especially when the branch outcome depends on unpredictable data, turning a simple filter into a performance hotspot. Understanding this lets engineers choose branchless formulations or reorder data to regain speed in critical code paths.
Written by elseif from the cluster below · every claim links back to a sourceThe three things worth knowing
The original version with a conditional test caused the processor to guess wrong about half the time for random inputs, adding roughly two milliseconds of delay on a typical 4 GHz processing unit.
Reserving space for the result container only improved the time by a few percent, showing that memory allocation was not the main bottleneck.
When the input was ordered so the test outcome became regular, the same filter ran more than four times faster, proving that predictability, not the branch itself, drives the cost.
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