BasicGasPricer.cpp

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/*
        This file is part of cpp-ethereum.

        cpp-ethereum is free software: you can redistribute it and/or modify
        it under the terms of the GNU General Public License as published by
        the Free Software Foundation, either version 3 of the License, or
        (at your option) any later version.

        cpp-ethereum is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        GNU General Public License for more details.

        You should have received a copy of the GNU General Public License
        along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
*/
#pragma warning(push)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#include <boost/math/distributions/normal.hpp>
#pragma warning(pop)
#pragma GCC diagnostic pop
#include "BasicGasPricer.h"
#include "BlockChain.h"
using namespace std;
using namespace dev;
using namespace dev::eth;

void BasicGasPricer::update(BlockChain const& _bc)
{
        unsigned c = 0;
        h256 p = _bc.currentHash();
        m_gasPerBlock = _bc.info(p).gasLimit();

        map<u256, u256> dist;
        u256 total = 0;

        // make gasPrice versus gasUsed distribution for the last 1000 blocks
        while (c < 1000 && p)
        {
                BlockHeader bi = _bc.info(p);
                if (bi.transactionsRoot() != EmptyTrie)
                {
                        auto bb = _bc.block(p);
                        RLP r(bb);
                        BlockReceipts brs(_bc.receipts(bi.hash()));
                        size_t i = 0;
                        for (auto const& tr: r[1])
                        {
                                Transaction tx(tr.data(), CheckTransaction::None);
                                u256 gu = brs.receipts[i].gasUsed();
                                dist[tx.gasPrice()] += gu;
                                total += gu;
                                i++;
                        }
                }
                p = bi.parentHash();
                ++c;
        }

        // fill m_octiles with weighted gasPrices
        if (total > 0)
        {
                m_octiles[0] = dist.begin()->first;

                // calc mean
                u256 mean = 0;
                for (auto const& i: dist)
                        mean += i.first * i.second;
                mean /= total;

                // calc standard deviation
                u256 sdSquared = 0;
                for (auto const& i: dist)
                        sdSquared += i.second * (i.first - mean) * (i.first - mean);
                sdSquared /= total;

                if (sdSquared)
                {
                        long double sd = sqrt(sdSquared.convert_to<long double>());
                        long double normalizedSd = sd / mean.convert_to<long double>();

                        // calc octiles normalized to gaussian distribution
                        boost::math::normal gauss(1.0, (normalizedSd > 0.01) ? normalizedSd : 0.01);
                        for (size_t i = 1; i < 8; i++)
                                m_octiles[i] = u256(mean.convert_to<long double>() * boost::math::quantile(gauss, i / 8.0));
                        m_octiles[8] = dist.rbegin()->first;
                }
                else
                {
                        for (size_t i = 0; i < 9; i++)
                                m_octiles[i] = (i + 1) * mean / 5;
                }
        }
}