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].cumulativeGasUsed();
                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;
        }
    }
}