votingworks · engineering

VxSuite Explainers

Interactive companions to VxSuite engineering changes.

• Same reads, different order

  How reordering ~3.7M pixel reads to match memory layout — and skipping the detailed pass unless a column earns it — made ballot streak detection 5× faster with bit-identical results.

  2026-08 · ballot-interpreter

• Eight histograms are faster than one

  Why the innocent-looking Otsu histogram loop was the slowest part of page preparation — and how eight interleaved shards halved it with zero SIMD, by giving the out-of-order core eight dependency chains instead of one.

  2026-08 · ballot-interpreter

• Sixty-four pixels at a time

  Finding each bubble means scoring 196 candidate positions. Packing every row of the comparison into a single 64-bit word — shift, OR, mask, popcount — made bubble scoring 6× faster with bit-identical scores, bounds, and fills.

  2026-08 · ballot-interpreter

• Every other line

  How the interpreter finds each ballot's QR code with one-dimensional scan lines watching for the finder patterns' 1:1:3:1:1 signature — and why scanning every other line is 41% faster with identical detections across the whole corpus.

  2026-08 · ballot-interpreter