| | 1 | # Order-preserving minimal perfect hash function generator |
| | 2 | |
| | 3 | Build order-preserving minimal perfect hash functions. |
| | 4 | |
| | 5 | [](https://codecov.io/gh/julian-klode/triehash) |
| | 6 | [](https://travis-ci.org/julian-klode/triehash) |
| | 7 | |
| | 8 | ## Performance |
| | 9 | |
| | 10 | Performance was evaluated against other hash functions. As an input set, the |
| | 11 | fields of Debian Packages and Sources files was used, and each hash function |
| | 12 | was run 1,000,000 times for each word. The byte count of the words were then |
| | 13 | summed up and divided by the total number of nanoseconds each function ran, so |
| | 14 | all speeds below are given in bytes per nanosecond, AKA gigabyte per second. |
| | 15 | |
| | 16 | arch/function|jak-x230 (amd64)|backup (amd64)|asachi.d.o (arm64)|asachi.d.o (armel)|asachi.d.o (armhf)|plummer.d.o (ppc64el)|eller.d.o (mipsel) |
| | 17 | -------------|----------------|--------------|------------------|------------------|------------------|---------------------|------------------ |
| | 18 | Trie | 2.4 | 1.9 | 1.2 | 0.9 | 0.8 | 2.0 | 0.2 |
| | 19 | Trie (*) | 2.2 | 1.7 | 0.8 | 0.7 | 0.7 | 1.8 | 0.2 |
| | 20 | re2c | 1.7 | 1.3 | 0.9 | 0.9 | 0.7 | 1.6 | 0.2 |
| | 21 | re2c (*) | 1.2 | 0.9 | 0.6 | 0.6 | 0.5 | 1.1 | 0.1 |
| | 22 | gperf (*) | 0.7 | 0.5 | 0.2 | 0.2 | 0.2 | 0.5 | 0.1 |
| | 23 | gperf | 1.3 | 0.9 | 0.3 | 0.3 | 0.2 | 0.4 | 0.1 |
| | 24 | djb (*) | 0.7 | 0.5 | 0.3 | 0.3 | 0.3 | 0.5 | 0.1 |
| | 25 | djb (**) | 1.0 | 0.7 | 0.4 | 0.5 | 0.5 | 0.6 | 0.2 |
| | 26 | djb | 0.9 | 0.7 | 0.5 | 0.5 | 0.5 | 0.7 | 0.2 |
| | 27 | apt (*) | 1.2 | 0.9 | 0.7 | 0.7 | 0.7 | 1.1 | 0.2 |
| | 28 | apt (**) | 2.3 | 1.7 | 0.7 | 0.9 | 0.8 | 1.9 | 0.2 |
| | 29 | |
| | 30 | And transposed: |
| | 31 | |
| | 32 | function/arch |Trie |Trie (*) |re2c |re2c (*) |gperf (*)|gperf |djb (*) |djb (**) |djb |apt (*) |apt (**) |
| | 33 | ---------------------|---------|---------|---------|---------|---------|---------|---------|---------|---------|---------|--------- |
| | 34 | jak-x230 (amd64) | 2.4| 2.2| 1.7| 1.2| 0.7| 1.3| 0.7| 1.0| 0.9| 1.2| 2.3 |
| | 35 | backup (amd64) | 1.9| 1.7| 1.3| 0.9| 0.5| 0.9| 0.5| 0.7| 0.7| 0.9| 1.7 |
| | 36 | asachi.d.o (arm64) | 1.2| 0.8| 0.9| 0.6| 0.2| 0.3| 0.3| 0.4| 0.5| 0.7| 0.7 |
| | 37 | asachi.d.o (armel) | 0.9| 0.7| 0.9| 0.6| 0.2| 0.3| 0.3| 0.5| 0.5| 0.7| 0.9 |
| | 38 | asachi.d.o (armhf) | 0.8| 0.7| 0.7| 0.5| 0.2| 0.2| 0.3| 0.5| 0.5| 0.7| 0.8 |
| | 39 | plummer.d.o (ppc64el)| 2.0| 1.8| 1.6| 1.1| 0.5| 0.4| 0.5| 0.6| 0.7| 1.1| 1.9 |
| | 40 | eller.d.o (mipsel) | 0.2| 0.2| 0.2| 0.1| 0.1| 0.1| 0.1| 0.2| 0.2| 0.2| 0.2 |
| | 41 | |
| | 42 | |
| | 43 | Legend: |
| | 44 | |
| | 45 | * The (*) variants are case-insensitive, (**) are more optimised versions |
| | 46 | of the (*) versions. |
| | 47 | * DJB (*) is a DJB Hash with naive lowercase conversion, DJB (**) just ORs one |
| | 48 | bit into each value to get alphabetical characters to be lowercase |
| | 49 | * APT (*) is the AlphaHash function from APT which hashes the last 8 bytes in a |
| | 50 | word in a case-insensitive manner. APT (**) is the same function unrolled. |
| | 51 | * All hosts except the x230 are Debian porterboxes. The x230 has a Core i5-3320M, |
| | 52 | barriere has an Opteron 23xx. |
| | 53 | |
| | 54 | Notes: |
| | 55 | |
| | 56 | * The overhead is larger than needed on some platforms due to gcc inserting |
| | 57 | unneeded zero extend instructions, see: |
| | 58 | https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77729 |
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