Plain C implementation of ProgPoW

This is a plain C implementation of ProgPoW. The progpow.c file is created by merging and revising pieces of (pseudo)code from different files in upstream ProgPoW (README.md, libethash-cl/CLMiner_kernel.cl, libprogpow/ProgPow.h, libethash-cuda/cuda_helper.h) and go-ethereum/consensus/ethash/progpow.go (the latter for clz() and popcount() only, which are trivial).

The uses of C++ references have been removed, but some structs are still passed and returned by value (allowed in C, just uncommon and inefficient).

The files under libethash are from https://github.com/ethereum/ethash and are used here to initialize the DAG for ProgPoW, which is the same as Ethash's.

Testing

On a Unix-like system, invoke make to build the progpow-test program. When run, it currently computes and caches on disk Ethash's ~1 GB DAG for block 30k, then computes ProgPoW using a set of nonce and header values found in upstream ProgPoW's test-vectors.md. The expected output is:

Light DAG init done
Full DAG init done
ProgPoW version 0.9.2
Block	30000
Digest	11f19805c58ab46610ff9c719dcf0a5f18fa2f1605798eef770c47219274767d
Result	5b7ccd472dbefdd95b895cac8ece67ff0deb5a6bd2ecc6e162383d00c3728ece
DAG	64 loads, 16384 bytes
Cache	12288 loads, 49152 bytes
Merge	36864 total (8192 12288 5120 11264)
Math	20480 total (2048 4096 2048 1024 2048 1024 4096 1024 1024 2048 0)

where the digest matches upstream ProgPoW's test-vectors.md.

To compute the proposed ProgPoW version 0.9.3 instead, uncomment -DPROGPOW_VERSION=93 in Makefile. The expected output becomes:

Light DAG init done
Full DAG init done
ProgPoW version 0.9.3
Block	30000
Digest	6018c151b0f9895ebe44a4ca6ce2829e5ba6ae1a68a4ccd05a67ac01219655c1
Result	34d8436444aa5c61761ce0bcce0f11401df2eace77f5c14ba7039b86b5800c08
DAG	64 loads, 16384 bytes
Cache	11264 loads, 45056 bytes
Merge	33792 total (8192 7168 10240 8192)
Math	18432 total (0 2048 0 5120 5120 0 0 0 4096 0 2048)

Known issues

This implementation of ProgPoW is effectively untested on big-endian because Ethash's included implementation of Keccak assumes little-endian (and more): https://github.com/coruus/keccak-tiny/issues/7

The included implementation of Ethash DAG initialization contains currently disabled code that would use SSE4.1 intrinsics for some speedup. That code is currently broken (at least) because the same implementation misaligns the data buffer (shifting it from the properly aligned mmap()'ed region by the 8-byte magic value, thereby never achieving the needed 16-byte alignment).

License

Both Ethereum's ethash and upstream ProgPoW were under GPLv3, which is how we get infected by that license. Some source files written from scratch (the test program and the Makefile) are also available under relaxed terms specified in those files.

Authors, maintainer, and contact information

This plain C implementation has been put together from the above sources and is maintained by:

Solar Designer <solar at openwall.com>

Ethash and ProgPoW are by their many corresponding authors. Comments in the Ethash source files under libethash specify several of their authors, but there are probably more as not every committer updated those comments.

The snippets of ProgPoW (pseudo)code included in progpow.c are apparently by ifdefelse, Radix Pi, and maybe other ProgPoW contributors. Ideally, proper copyright statements need to be identified and added, but upstream ProgPoW currently lacks those as well.

Related work

Other implementations of ProgPoW exist in:

• https://github.com/ifdefelse/ProgPOW (C++ with mandatory CUDA or OpenCL)
• https://github.com/ifdefelse/go-ethereum (Go)
• https://github.com/chfast/ethash (C++)

Those are larger source trees that are not as focused on ProgPoW itself/alone as this one is.