See also: Rules and Conditions

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  • Facilitate research and development of new and existing algorithms for universal lossless data compression.
  • Bring attention to lossless data compression, spur activity in the field and encourage more researchers and practitioners to pursue it.

We conceived this competition as a long-term project with annual events. Participation is free. Winners will receive substantial monetary prizes and formal awards; the total prize pool this year is 50,000 EUR.



In this competition we concentrate on the advantages of algorithms and their implementations for universal lossless data compression, rather than tuning for certain data types. We test compressors under the following scenarios:

  • Qualitative-data compression. This year we use text data.
  • Quantitative-data compression. The test set for this year contains images, most of which are photographic.
  • Mixed-data compression. This year our focus is on slightly preprocessed executable files (we removed incompressible chunks).
  • Small-block-data compression. We use small blocks of textual and mixed data to evaluate how compressors behave when the data size is severely limited, such as in block-storage systems.

To align compressors by speed and consider practical use cases, we impose speed limits to separate each test into three subcategories: rapid compression, balanced compression and high compression ratio. All told, the result is 12 categories and leaderboards for this competition, as the table below illustrates.

We offer the following awards for each category by compressor rank:

  • First place: 3,000 EUR and award certificate
  • Second place: 1,000 EUR and award certificate
  • Third place: honorable mention certificate (no monetary prize)

We’re also reserving 2,000 EUR for additional rewards in case of ties or other difficult situations.

So, this competition has 12 separate categories and leaderboards, each with its own prizes. It’s not necessary to make a universal solution.

Test Type


Compression + Decompression Time Limit, seconds

Test 1. Qualitative data (text only).
Size = 1 GB.

T1 Rapid compression

< 40

T1 Balanced compression

< 400

T1 High compression ratio

< 4000

Test 2. Quantitative data (images only).
Size = approximately 1 GB.

T2 Rapid compression

< 40

T2 Balanced compression

< 400

T2 High compression ratio

< 4000

Test 3. Mixed data (preprocessed executable files).
Size = 1 GB.

T3 Rapid compression

< 40

T3 Balanced compression

< 400

T3 High compression ratio

< 4000

Test 4. Block compression (mixed Test 1 and Test 3 data).
Size = approximately 1 GB in 32 KiB blocks to be compressed independently so as to allow random-access decompression.

T4 Rapid compression

< 40

T4 Balanced compression

< 400

T4 High compression ratio

< 4000


In all cases we add the compressed-decompressor size to the compressed-data size and call it the “compressed-data full size”:

c_full_size = c_size + c_decompressor_size.

For rapid-compression categories we rank compressors by the following formula:

f = c_time + A × d_time + B × c_full_size,


  • A is a coefficient that defines the relative importance of decompression speed versus compression speed, and
  • B is the significance ratio of processing speed to compressed-data full size,
  • c_time and d_time are in seconds, c_full_size is in bytes.

This year we use the formula with the following coefficients:

f = c_time + 2 × d_time + (1 / 1,000,000) × c_full_size.

Within each category, we compute f for every compressor, sort the values in ascending order and assign each one a rank equal to its position in the list. Therefore, first place goes to the compressor with the smallest f value and so on.

For the balanced-compression and high-compression-ratio categories, we order results by compressed-data full size only. Thus, among all compressors that meet the compression + decompression time limit in a given category, the winner is the one that produces the smallest output data.

For the block-compression test we measure compression and decompression times with initialization procedures running only once before compression or decompression of the first block. Input and output data are stored in RAM.

Who Can Submit

Developers and owners of new or existing compression software (compressors) may compete, either as individuals or groups. Participation is free!

This competition is sponsored by Huawei. The test method and result validity are the sole responsibility of the organizer (“we” in this text), the Graphics & Media Lab of the Computational Mathematics and Cybernetics Department at Moscow State University.


Check back in July for the latest leaderboards!