Rectfillcurve – generate rectangle-filling curves
How do you visit every coordinate in an NxM grid once? The easiest is to process line-by-line, from the first to last column, but if you want better caching you might try alternating the column direction for each row. The Morton/Z-order and Hilbert order give even better cache coherency for some tasks, although the classic versions only work on squares with power-of-two length sides. Luckily for me, people have developed generalized versions of those algorithms which can handle arbitrary-sized rectangles. I've taken those and packaged all of the those curves into "rectfillcurve", with…
Rectfillcurve – generate rectangle-filling curves launched on July 17, 2023 with 24 votes, #1,456 of 4,347 launches that month and more than 75% of that year's launches. The site was still online in September 2026, 3 years on.
In plain words
Rectfillcurve generates algorithms for visiting every coordinate in a rectangular grid exactly once, optimizing for cache performance. It implements multiple curve-filling approaches including row-by-row, alternating directions, Morton/Z-order, and Hilbert order curves, along with a pseudo-random option. The tool handles arbitrary-sized rectangles through generalized algorithms, offering an iterator API and available in both C and Python for developers working with spatial data structures.
written from the facts on this page · September 2026
From the sources
A standalone C library and Python extension module for generating space-filling curves for arbitrary-sized rectangles through an iterator API. (See Background for details.) "hilbert_classic" - the classic Hilbert curve , which requires a square with lengths which are a power of 2 in size (or 0x0). "morton_classic" - the classic Morton/Z-order curve , which requires a square with lengths which are a power of 2 in size (or 0x0). "mlcg" - use a multiplicative linear congruential generator to visit the coordinates in a random-like order. The rectangles are described by (width, height), with coordinates (i, j) where 0 <= i < width and 0 <=j < height. There is also an option to flip the…from hg.sr.ht
In the maker’s words, at launch
How do you visit every coordinate in an NxM grid once? The easiest is to process line-by-line, from the first to last column, but if you want better caching you might try alternating the column direction for each row. The Morton/Z-order and Hilbert order give even better cache coherency for some tasks, although…
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Source: Show HN post ↗ · launch text quoted in part
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