Feature/htr

[ferranbt]

This PR includes support for two things:

• Byte slices (i.e. [32]byte)
• Hashing of the structs with the function HashTreeRoot.

[prestonvanloon]

Please add a HashTreeRoot interface so we can do checks like this:

if v, ok := object.(ssz.HashTreeRooter); ok {
  return v.HashTreeRoot()
}

Edit: nevermind, i see you already did that. Thanks!

[prestonvanloon]

I tried this locally and it appears to be missing imports that worked previously.

v1alpha1 is still used in this file, but import was removed when I used this branch.

[prestonvanloon]

Would it be possible to change the return type to [32]byte, error?
This would be inline with go-ssz.HashTreeRoot and other custom implementations in Prysm.

[ferranbt]

Sure, no problem

[prestonvanloon]

Here's some benchmarks I ran to compare this against go-ssz.HashTreeRoot. Please don't interpret the execution time to be how long HTR takes, this benchmark was reading files from disk, unmarshalling, marshalling, and some byte comparisions against spec tests.

test.log

[ferranbt]

The 'htr_off' benchmarks are done with go-ssz or with the custom functions in prysm? I am not getting the same results on my benchmarks. I used this Htr benchmark for both fastssz and go-ssz and got:

goos: linux
goarch: amd64
pkg: github.com/ferranbt/fastssz/spectests
BenchmarkHashTreeRootFast
BenchmarkHashTreeRootFast-8    	    8347	    138159 ns/op	       0 B/op	       0 allocs/op
BenchmarkHashTreeRootGoSSZ
BenchmarkHashTreeRootGoSSZ-8   	     724	   1440258 ns/op	  264128 B/op	    6638 allocs/op
PASS
ok  	github.com/ferranbt/fastssz/spectests	3.120s

where 'BenchmarkHashTreeRootGoSSZ' is

import (
	oldSSZ "github.com/prysmaticlabs/go-ssz"
)

func BenchmarkHashTreeRootGoSSZ(b *testing.B) {
	obj := new(BeaconBlock)
	readValidGenericSSZ(nil, benchmarkTestCase, obj)

	b.ReportAllocs()
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		goSSZ.HashTreeRoot(obj)
	}
}

The numbers seem accurate for fastssz. The implementation reuses all the memory and the main factor that accounts for most of the time consumed is the sha hashing.

[prestonvanloon]

The 'htr_off' benchmarks are done with go-ssz or with the custom functions in prysm?

They are done with go-ssz, except for the BeaconState which uses its custom HTR function. As I mentioned before, don't interpret these times as HTR only, it does a lot more than only HTR. Here's the benchmark on a working branch: https://github.com/prysmaticlabs/prysm/blob/d89a4af4637b5fe00e3ad242d55f70ba8de3be39/proto/testing/ssz_static_mainnet_test.go#L11