forked from cerc-io/plugeth
58 lines
2.4 KiB
Go
58 lines
2.4 KiB
Go
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// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// +build go1.8
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package pow
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import "math/big"
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// cacheSize calculates and returns the size of the ethash verification cache that
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// belongs to a certain block number. The cache size grows linearly, however, we
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// always take the highest prime below the linearly growing threshold in order to
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// reduce the risk of accidental regularities leading to cyclic behavior.
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func cacheSize(block uint64) uint64 {
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// If we have a pre-generated value, use that
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epoch := int(block / epochLength)
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if epoch < len(cacheSizes) {
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return cacheSizes[epoch]
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}
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// No known cache size, calculate manually (sanity branch only)
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size := uint64(cacheInitBytes + cacheGrowthBytes*uint64(epoch) - hashBytes)
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for !new(big.Int).SetUint64(size / hashBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
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size -= 2 * hashBytes
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}
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return size
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}
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// datasetSize calculates and returns the size of the ethash mining dataset that
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// belongs to a certain block number. The dataset size grows linearly, however, we
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// always take the highest prime below the linearly growing threshold in order to
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// reduce the risk of accidental regularities leading to cyclic behavior.
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func datasetSize(block uint64) uint64 {
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// If we have a pre-generated value, use that
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epoch := int(block / epochLength)
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if epoch < len(datasetSizes) {
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return datasetSizes[epoch]
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}
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// No known dataset size, calculate manually (sanity branch only)
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size := uint64(datasetInitBytes + datasetGrowthBytes*uint64(epoch) - mixBytes)
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for !new(big.Int).SetUint64(size / mixBytes).ProbablyPrime(1) { // Always accurate for n < 2^64
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size -= 2 * mixBytes
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}
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return size
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}
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