Compression level 7

Benchmark index · Median overview · ← Level 6 · Level 8 →

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 7

Implementation	Median speed / C ↑	Median output / C ↓	Datasets
zstd C	1.000×	1.000×	8
mzstd	1.244×	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: 10.730×; output: 9 / 9 bytes.

Level 7: 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	2,199	2,141–2,271	—	9	—	1.000×
mzstd	204.9	200.3–210.4	—	9	—	10.730×

tiny-text

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

mzstd speed / C: 5.314×; output: 53 / 53 bytes.

Level 7: 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	2.423	2.408–2.441	17.32	53	120.455%	1.000×
mzstd	0.456	0.4403–0.4753	92.01	53	120.455%	5.314×

repeated-1m

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

mzstd speed / C: 2.427×; output: 49 / 49 bytes.

Level 7: 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	364.1	352.6–378.6	2,746.15	49	0.005%	1.000×
mzstd	150.1	146.9–153.4	6,664.32	49	0.005%	2.427×

binary-64k

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

mzstd speed / C: 1.334×; output: 1,270 / 1,270 bytes.

Level 7: 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	33.35	32.71–34.34	1,874.19	1,270	1.938%	1.000×
mzstd	24.99	24.46–25.59	2,500.72	1,270	1.938%	1.334×

random-64k

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

mzstd speed / C: 1.154×; output: 65,546 / 65,546 bytes.

Level 7: 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	27.42	26.71–28.21	2,279.41	65,546	100.015%	1.000×
mzstd	23.76	23.2–24.36	2,629.99	65,546	100.015%	1.154×

random-1m

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

mzstd speed / C: 1.042×; output: 1,048,609 / 1,048,609 bytes.

Level 7: 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	328.9	320.5–337	3,040.69	1,048,609	100.003%	1.000×
mzstd	315.6	308.2–322.8	3,168.42	1,048,609	100.003%	1.042×

text-1m

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

mzstd speed / C: 0.986×; output: 52,804 / 52,804 bytes.

Level 7: 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	1,897	1,842–1,955	527.22	52,804	5.036%	1.000×
mzstd	1,923	1,858–1,990	519.92	52,804	5.036%	0.986×

alice29

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

mzstd speed / C: 0.929×; output: 53,195 / 53,195 bytes.

Level 7: 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	1,645	1,621–1,674	88.18	53,195	34.976%	1.000×
mzstd	1,770	1,738–1,806	81.94	53,195	34.976%	0.929×

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