Compression level -1

Benchmark index · Median overview · ← Level -5 · Level 1 →

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.

Median speed and output relative to C at level -1

Implementation	Median speed / C ↑	Median output / C ↓	Datasets
zstd C	1.000×	1.000×	8
mzstd	1.633×	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 · binary-64k · random-64k · random-1m · text-1m · alice29

empty

Empty input; measures API overhead. Input: 0 bytes.

mzstd speed / C: 11.441×; output: 9 / 9 bytes.

Level -1: empty speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, ns	95% mean interval, ns	MiB/s	Output bytes	Output / input	Speed / C
zstd C	2,299	2,231–2,374	—	9	—	1.000×
mzstd	200.9	193.6–209.1	—	9	—	11.441×

tiny-text

44-byte quick-brown-fox sentence. Input: 44 bytes.

mzstd speed / C: 9.111×; output: 53 / 53 bytes.

Level -1: tiny-text speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, µs	95% mean interval, µs	MiB/s	Output bytes	Output / input	Speed / C
zstd C	2.645	2.535–2.771	15.86	53	120.455%	1.000×
mzstd	0.2903	0.2849–0.2965	144.53	53	120.455%	9.111×

repeated-1m

1 MiB of repeated a bytes. Input: 1,048,576 bytes.

mzstd speed / C: 2.735×; output: 51 / 51 bytes.

Level -1: repeated-1m speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, µs	95% mean interval, µs	MiB/s	Output bytes	Output / input	Speed / C
zstd C	78.12	76.16–80.59	12,800.99	51	0.005%	1.000×
mzstd	28.56	28.21–29.04	35,014.71	51	0.005%	2.735×

binary-64k

64 KiB of structured binary bytes: ((i / 16) XOR i) modulo 256. Input: 65,536 bytes.

mzstd speed / C: 1.738×; output: 2,442 / 2,442 bytes.

Level -1: binary-64k speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, µs	95% mean interval, µs	MiB/s	Output bytes	Output / input	Speed / C
zstd C	11.1	10.64–11.6	5,630.72	2,442	3.726%	1.000×
mzstd	6.386	6.19–6.601	9,787.28	2,442	3.726%	1.738×

random-64k

64 KiB prefix of the deterministic pseudorandom corpus. Input: 65,536 bytes.

mzstd speed / C: 1.528×; output: 65,546 / 65,546 bytes.

Level -1: random-64k speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, µs	95% mean interval, µs	MiB/s	Output bytes	Output / input	Speed / C
zstd C	6.803	6.705–6.93	9,187.22	65,546	100.015%	1.000×
mzstd	4.453	4.352–4.57	14,036.88	65,546	100.015%	1.528×

random-1m

1 MiB of deterministic xorshift64 pseudorandom bytes. Input: 1,048,576 bytes.

mzstd speed / C: 1.122×; output: 1,048,610 / 1,048,610 bytes.

Level -1: random-1m speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, µs	95% mean interval, µs	MiB/s	Output bytes	Output / input	Speed / C
zstd C	70.51	69.28–71.86	14,181.86	1,048,610	100.003%	1.000×
mzstd	62.84	61.8–63.93	15,913.72	1,048,610	100.003%	1.122×

text-1m

Alice text repeated cyclically to 1 MiB. Input: 1,048,576 bytes.

mzstd speed / C: 1.085×; output: 80,894 / 80,894 bytes.

Level -1: text-1m speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, µs	95% mean interval, µs	MiB/s	Output bytes	Output / input	Speed / C
zstd C	438.2	425.7–451.1	2,282.31	80,894	7.715%	1.000×
mzstd	403.7	391–417.2	2,477.15	80,894	7.715%	1.085×

alice29

Alice in Wonderland text from the Canterbury corpus (testdata/alice29.txt). Input: 152,089 bytes.

mzstd speed / C: 0.953×; output: 71,645 / 71,645 bytes.

Level -1: alice29 speed and compressed size

Exact measurements and confidence bounds

Implementation	Mean, µs	95% mean interval, µs	MiB/s	Output bytes	Output / input	Speed / C
zstd C	390.8	378–405.8	371.14	71,645	47.107%	1.000×
mzstd	410	395.3–426.5	353.73	71,645	47.107%	0.953×

Keyboard shortcuts

mzstd