Compression level 4
Benchmark index · Median overview · ← Level 3 · Level 5 →
Recorded run: long-20261109 (2026-11-09). Raw results · Environment · Run analysis.
Median across all datasets
Each of the 8 datasets has equal weight, including empty and tiny input. Speed / C = C mean latency / implementation mean latency; output / C = implementation bytes / C bytes. We take the median of these 8 per-dataset ratios separately for speed and size. 1× matches C; higher speed and lower output are better. These are medians across datasets, not median sample latencies, and do not imply statistical significance.
| Implementation | Median speed / C ↑ | Median output / C ↓ | Datasets |
|---|---|---|---|
| zstd C | 1.000× | 1.000× | 8 |
| mzstd | 1.163× | 1.000× | 8 |
Measurement setup and interpretation
zstd 1.5.7 (the C library built by zstd-ffi) and mzstd at the recorded
working tree compress identical bytes at this level. Every frame was checked byte-identical
to zstd’s and decoded back to its input before any timing.
These are cold native API measurements: construction, allocation, compression, and disposal. Complete known input; 50 samples, 3 s warmup, at least 6 s measurement. Host: AMD Ryzen 9 7950X, Linux KVM guest with two vCPUs: the encoder suite, then the decoder suite, each in one Criterion process pinned to vCPU 1; nothing else ran in the guest. Other tenants loaded the host: a fixed C decode varied by 8-43% (p10-p90 wall time) through the day, so sampling was lengthened to average over the noise. unset; Cargo release defaults (bench profile), runtime SIMD dispatch (AVX-512 level on this host; the decoder runs its block loops at the AVX2 level).
Chart whiskers and table intervals describe 95% confidence bounds on mean timing. They do not capture all host or allocator variation. Throughput bounds are transformed latency bounds. Output / input is compressed bytes divided by input bytes; smaller is better, and values above 100% mean expansion. For empty input, throughput and output / input are undefined (—). See the run analysis for measurement limitations.
Dataset details
Ordered by mzstd speed / C, highest first; all 8 datasets are shown. This order uses recorded mean latency, not statistical significance. Bars start at zero.
empty · tiny-text · repeated-1m · text-1m · random-64k · binary-64k · alice29 · random-1m
empty
Empty input; measures API overhead. Input: 0 bytes.
mzstd speed / C: 10.888×; output: 9 / 9 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, ns | 95% mean interval, ns | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 2,254 | 2,179–2,342 | — | 9 | — | 1.000× |
| mzstd | 207 | 203.6–210.9 | — | 9 | — | 10.888× |
tiny-text
44-byte quick-brown-fox sentence. Input: 44 bytes.
mzstd speed / C: 5.462×; output: 53 / 53 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, µs | 95% mean interval, µs | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 2.455 | 2.403–2.517 | 17.09 | 53 | 120.455% | 1.000× |
| mzstd | 0.4495 | 0.4378–0.4649 | 93.35 | 53 | 120.455% | 5.462× |
repeated-1m
1 MiB of repeated a bytes. Input: 1,048,576 bytes.
mzstd speed / C: 3.084×; output: 50 / 50 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, µs | 95% mean interval, µs | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 164.7 | 158.5–171.9 | 6,071.32 | 50 | 0.005% | 1.000× |
| mzstd | 53.4 | 52.48–54.46 | 18,726.54 | 50 | 0.005% | 3.084× |
text-1m
Alice text repeated cyclically to 1 MiB. Input: 1,048,576 bytes.
mzstd speed / C: 1.180×; output: 55,760 / 55,760 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, µs | 95% mean interval, µs | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 755.3 | 734–777.7 | 1,324.02 | 55,760 | 5.318% | 1.000× |
| mzstd | 639.8 | 620.2–661.1 | 1,563.00 | 55,760 | 5.318% | 1.180× |
random-64k
64 KiB prefix of the deterministic pseudorandom corpus. Input: 65,536 bytes.
mzstd speed / C: 1.145×; output: 65,546 / 65,546 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, µs | 95% mean interval, µs | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 18.74 | 18.23–19.29 | 3,335.66 | 65,546 | 100.015% | 1.000× |
| mzstd | 16.37 | 16–16.79 | 3,818.29 | 65,546 | 100.015% | 1.145× |
binary-64k
64 KiB of structured binary bytes: ((i / 16) XOR i) modulo 256. Input: 65,536 bytes.
mzstd speed / C: 1.078×; output: 3,909 / 3,909 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, µs | 95% mean interval, µs | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 102.9 | 99.89–106.2 | 607.67 | 3,909 | 5.965% | 1.000× |
| mzstd | 95.37 | 92.92–98.36 | 655.36 | 3,909 | 5.965% | 1.078× |
alice29
Alice in Wonderland text from the Canterbury corpus (testdata/alice29.txt). Input: 152,089 bytes.
mzstd speed / C: 0.979×; output: 54,282 / 54,282 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, µs | 95% mean interval, µs | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 1,007 | 968.5–1,051 | 144.04 | 54,282 | 35.691% | 1.000× |
| mzstd | 1,029 | 1,001–1,059 | 141.01 | 54,282 | 35.691% | 0.979× |
random-1m
1 MiB of deterministic xorshift64 pseudorandom bytes. Input: 1,048,576 bytes.
mzstd speed / C: 0.940×; output: 1,048,609 / 1,048,609 bytes.
Exact measurements and confidence bounds
| Implementation | Mean, µs | 95% mean interval, µs | MiB/s | Output bytes | Output / input | Speed / C |
|---|---|---|---|---|---|---|
| zstd C | 126.1 | 124.3–128.3 | 7,929.46 | 1,048,609 | 100.003% | 1.000× |
| mzstd | 134.2 | 132.1–136.8 | 7,452.21 | 1,048,609 | 100.003% | 0.940× |