bd4e5c21dc
This adds functions to calculate a merkle root to the blockchain/standalone module. Rather than copying the existing functions from blockchain, it introduces new optimized functions that have simpler code and are also generally easier to use. The new functions simply return the calculated root instead of all of the intermediate hashes which no known callers were actually using anyway. It also adds a basic usage example, benchmarks, updates the documentation and includes comprehensive tests. As can be seen by the benchmarks below, the new code isn't significantly faster in terms of execution speed since it is still dominated by the actual hashing, however, it does significantly reduce the number of allocations which reduces pressure on the GC, particularly during bursty situations such as IBD. It also scales much better to larger numbers of transactions. The following is a before and after comparison of calculating merkle roots for various numbers of leaves: benchmark old ns/op new ns/op delta --------------------------------------------------------------- BenchmarkCalcMerkleRoot/20 25637 24287 -5.27% BenchmarkCalcMerkleRoot/1000 1252749 1209130 -3.48% BenchmarkCalcMerkleRoot/2000 2601754 2343198 -9.94% BenchmarkCalcMerkleRoot/4000 4873969 4629169 -5.02% BenchmarkCalcMerkleRoot/8000 9831116 9270095 -5.71% BenchmarkCalcMerkleRoot/16000 19172545 19067585 -0.55% BenchmarkCalcMerkleRoot/32000 37980323 35746500 -5.88% benchmark old allocs new allocs delta ---------------------------------------------------------------- BenchmarkCalcMerkleRoot/20 106 64 -39.62% BenchmarkCalcMerkleRoot/1000 5006 3004 -39.99% BenchmarkCalcMerkleRoot/2000 10006 6004 -40.00% BenchmarkCalcMerkleRoot/4000 20006 12004 -40.00% BenchmarkCalcMerkleRoot/8000 40006 24004 -40.00% BenchmarkCalcMerkleRoot/16000 80006 48004 -40.00% BenchmarkCalcMerkleRoot/32000 160006 96004 -40.00% benchmark old bytes new bytes delta ---------------------------------------------------------------- BenchmarkCalcMerkleRoot/20 6896 4432 -35.73% BenchmarkCalcMerkleRoot/1000 320688 208272 -35.05% BenchmarkCalcMerkleRoot/2000 641072 416272 -35.07% BenchmarkCalcMerkleRoot/4000 1281840 832272 -35.07% BenchmarkCalcMerkleRoot/8000 2563376 1664272 -35.07% BenchmarkCalcMerkleRoot/16000 5126448 3328272 -35.08% BenchmarkCalcMerkleRoot/32000 10252592 6656273 -35.08%
98 lines
2.9 KiB
Go
98 lines
2.9 KiB
Go
// Copyright (c) 2014-2016 The btcsuite developers
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// Copyright (c) 2015-2019 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package standalone_test
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import (
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"fmt"
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"math/big"
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"github.com/decred/dcrd/blockchain/standalone"
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"github.com/decred/dcrd/chaincfg/chainhash"
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)
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// This example demonstrates how to convert the compact "bits" in a block header
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// which represent the target difficulty to a big integer and display it using
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// the typical hex notation.
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func ExampleCompactToBig() {
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// Convert the bits from block 1 in the main chain.
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bits := uint32(453115903)
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targetDifficulty := standalone.CompactToBig(bits)
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// Display it in hex.
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fmt.Printf("%064x\n", targetDifficulty.Bytes())
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// Output:
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// 000000000001ffff000000000000000000000000000000000000000000000000
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}
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// This example demonstrates how to convert a target difficulty into the compact
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// "bits" in a block header which represent that target difficulty.
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func ExampleBigToCompact() {
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// Convert the target difficulty from block 1 in the main chain to compact
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// form.
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t := "000000000001ffff000000000000000000000000000000000000000000000000"
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targetDifficulty, success := new(big.Int).SetString(t, 16)
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if !success {
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fmt.Println("invalid target difficulty")
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return
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}
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bits := standalone.BigToCompact(targetDifficulty)
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fmt.Println(bits)
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// Output:
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// 453115903
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}
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// This example demonstrates checking the proof of work of a block hash against
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// a target difficulty.
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func ExampleCheckProofOfWork() {
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// This is the pow limit for mainnet and would ordinarily come from chaincfg
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// params, however, it is hard coded here for the purposes of the example.
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l := "00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
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powLimit, success := new(big.Int).SetString(l, 16)
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if !success {
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fmt.Println("invalid pow limit")
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return
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}
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// Check the proof of work for block 1 in the main chain.
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h := "000000000000437482b6d47f82f374cde539440ddb108b0a76886f0d87d126b9"
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hash, err := chainhash.NewHashFromStr(h)
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if err != nil {
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fmt.Printf("failed to parse hash: %v\n", err)
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return
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}
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bits := uint32(453115903)
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if err := standalone.CheckProofOfWork(hash, bits, powLimit); err != nil {
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fmt.Printf("proof of work check failed: %v\n", err)
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return
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}
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// Output:
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//
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}
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// This example demonstrates calculating a merkle root from a slice of leaf
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// hashes.
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func ExampleCalcMerkleRoot() {
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// Create a slice of the leaf hashes.
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leaves := make([]chainhash.Hash, 3)
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for i := range leaves {
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// The hash would ordinarily be calculated from the TxHashFull function
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// on a transaction, however, it's left as a zero hash for the purposes
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// of this example.
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leaves[i] = chainhash.Hash{}
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}
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merkleRoot := standalone.CalcMerkleRoot(leaves)
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fmt.Printf("Result: %s", merkleRoot)
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// Output:
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// Result: 5fdfcaba377aefc1bfc4af5ef8e0c2a61656e10e8105c4db7656ae5d58f8b77f
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}
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