This is an adaptation of Genesis Code, a new generation erasure code technology developed by Genesis Codes inventor Anthony Mai, into the JavaReedSolomon, open source project of Backblaze's original simple and efficient Reed-Solomon implementation in Java, which was originally built at Backblaze. There is an overview of how the Reed Solomon algorithm works in their blog post.
Reed Solomon Code, invented in 1960 and refined over the years, is slow and inefficient, with computation complexity increases in the quadratic power of code length. Genesis Codes is a superior replacement with complexity scales only linearly, or even sub-linearly in some cases.
The ReedSolomon class does the encoding and decoding, and is supported by Matrix, which does matrix arithmetic, and Galois, which is a finite field over 8-bit values.
For examples of how to use ReedSolomon, take a look at SampleEncoder and SampleDecoder. They show, in a very simple way, how to break a file into shards and encode parity, and then how to take a subset of the shards and reconstruct the original file.
There is a Gradle build file to make a jar and run the tests. Running it is simple. At the root folder just type: gradle build.
Then you need to go to the newly created build folder and put the JNI component of Genesis Codes, named libgenesis.so. You will have to get the file from Anthony Mai, who invented Genesis Codes. I cannot make the JNI component available publicly because it is my trade secret. I can be reached at [email protected] or find me at LinkedIn.
To try out Genesis encoding/decoding, type this command under build: java -Djava.library.path=. -cp ./classes/java/main com/genesis/GenesisEncoder somefile.txt
I would also like to send out a special thanks to James Plank at the University of Tennessee at Knoxville for his useful papers on erasure coding. If you'd like an intro into how it all works, take a look at this introductory paper.
This project is meant to demonstrate usage of Genesis Code in Java. If you need more speed, consult the Genesis Code inventor for help. You may be interested in using the Intel SIMD instructions to speed up the Galois field multiplication. You can read more about that in the paper on Screaming Fast Galois Field Arithmetic.
The following are original performance notes of Reed Solomon Code. On initial evaluation, Genesis Codes delivers multi-GB per seconds throughput on the same platform, and is up to a hundred times faster.
The performance of the inner loop depends on the specific processor you're running on. There are twelve different permutations of the loop in this library, and the ReedSolomonBenchmark class will tell you which one is faster for your particular application. The number of parity and data shards in the benchmark, as well as the buffer sizes, match the usage at Backblaze. You can set the parameters of the benchmark to match your specific use before choosing a loop implementation.
These are the speeds I got running the benchmark on a Backblaze storage pod:
ByteInputOutputExpCodingLoop 95.2 MB/s
ByteInputOutputTableCodingLoop 107.0 MB/s
ByteOutputInputExpCodingLoop 130.3 MB/s
ByteOutputInputTableCodingLoop 181.4 MB/s
InputByteOutputExpCodingLoop 94.4 MB/s
InputByteOutputTableCodingLoop 138.3 MB/s
InputOutputByteExpCodingLoop 200.4 MB/s
InputOutputByteTableCodingLoop 525.7 MB/s
OutputByteInputExpCodingLoop 143.7 MB/s
OutputByteInputTableCodingLoop 209.5 MB/s
OutputInputByteExpCodingLoop 217.6 MB/s
OutputInputByteTableCodingLoop 515.7 MB/s
