mirror of https://github.com/zcash/zips.git
Switch from a constant value per block to a block reward fraction
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Jack Grigg
parent
2c4989a120
commit
41e077a354
61
zip-0207.rst
61
zip-0207.rst
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@ -45,12 +45,18 @@ Specification
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Funding streams
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---------------
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A funding stream is defined by a constant value per block (in zatoshis), a start height (inclusive), and an
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end height (exclusive). The start height MUST be after the end of the mining slow-start (to make specification
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of the value simpler).
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A funding stream is defined by a block reward fraction (represented as a numerator and a denominator), a start
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height (inclusive), and an end height (exclusive).
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- To-do: Decide whether to use fractional value per block instead, which gets around the mining slow-start
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problem (and halvings) but might make implementation more complex.
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By defining the issuance as a proportion of the total block issuance, rather than absolute zatoshis, this ZIP
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dovetails with any changes to both block target times and issuance-per-block rates while maintaining an
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unchanged target-time-based issuance schedule. We anticipate such target-time / issuance rate changes in other
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ZIPs.
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The value of a funding stream at a given block height is defined as::
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FundingStream.Value(height) =
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floor((BlockReward(height) * FundingStream.ValueNumerator) / FundingStream.ValueDenominator)
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An active funding stream at a given block height is defined as a funding stream for which the block height is
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less than its end height, but not less than its start height.
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@ -84,13 +90,13 @@ Stream definitions
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The three logical funding streams described above each start at the Blossom activation height, and end at the
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first block reward halving. They are defined as follows:
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======== ================ ================== ================================
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Stream Value (zatoshis) Start height End height
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======== ================ ================== ================================
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FR 184250000 Blossom activation SlowStartShift + HalvingInterval
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ZF E 36000000 Blossom activation SlowStartShift + HalvingInterval
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ZECC SR 29750000 Blossom activation SlowStartShift + HalvingInterval
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======== ================ ================== ================================
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======== =============== ================= ================== ================================
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Stream Value numerator Value denominator Start height End height
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======== =============== ================= ================== ================================
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FR 737 1000 Blossom activation SlowStartShift + HalvingInterval
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ZF E 144 1000 Blossom activation SlowStartShift + HalvingInterval
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ZECC SR 119 1000 Blossom activation SlowStartShift + HalvingInterval
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======== =============== ================= ================== ================================
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- To-do: specify the correct values.
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- To-do: specify the correct start height.
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@ -120,7 +126,8 @@ Example implementation
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struct FundingPeriod {
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std::vector<std::string> addresses,
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CAmount value,
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uint64_t valueNumerator,
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uint64_t valueDenominator,
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int startHeight,
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int endHeight,
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};
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@ -142,29 +149,38 @@ Example implementation
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...
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consensus.vFundingPeriods[Consensus::FS_FR].addresses = FS_ADDRESSES_FR;
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consensus.vFundingPeriods[Consensus::FS_FR].value = 184250000;
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consensus.vFundingPeriods[Consensus::FS_FR].valueNumerator = 737;
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consensus.vFundingPeriods[Consensus::FS_FR].valueDenominator = 1000;
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consensus.vFundingPeriods[Consensus::FS_FR].startHeight =
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consensus.vUpgrades[Consensus::UPGRADE_BLOSSOM].nActivationHeight;
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consensus.vFundingPeriods[Consensus::FS_FR].endHeight =
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(consensus.nSubsidySlowStartInterval / 2) + consensus.nSubsidyHalvingInterval;
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assert(consensus.vFundingPeriods[Consensus::FS_FR].valueNumerator <
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consensus.vFundingPeriods[Consensus::FS_FR].valueDenominator);
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assert(consensus.vFundingPeriods[Consensus::FS_FR].startHeight <
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consensus.vFundingPeriods[Consensus::FS_FR].endHeight);
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consensus.vFundingPeriods[Consensus::FS_ZF_E].addresses = FS_ADDRESSES_ZF_E;
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consensus.vFundingPeriods[Consensus::FS_ZF_E].value = 36000000;
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consensus.vFundingPeriods[Consensus::FS_ZF_E].valueNumerator = 144;
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consensus.vFundingPeriods[Consensus::FS_ZF_E].valueDenominator = 1000;
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consensus.vFundingPeriods[Consensus::FS_ZF_E].startHeight =
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consensus.vUpgrades[Consensus::UPGRADE_BLOSSOM].nActivationHeight;
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consensus.vFundingPeriods[Consensus::FS_ZF_E].endHeight =
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(consensus.nSubsidySlowStartInterval / 2) + consensus.nSubsidyHalvingInterval;
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assert(consensus.vFundingPeriods[Consensus::FS_ZF_E].valueNumerator <
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consensus.vFundingPeriods[Consensus::FS_ZF_E].valueDenominator);
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assert(consensus.vFundingPeriods[Consensus::FS_ZF_E].startHeight <
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consensus.vFundingPeriods[Consensus::FS_ZF_E].endHeight);
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].addresses = FS_ADDRESSES_ZECC_SR;
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].value = 29750000;
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].valueNumerator = 119;
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].valueDenominator = 1000;
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].startHeight =
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consensus.vUpgrades[Consensus::UPGRADE_BLOSSOM].nActivationHeight;
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].endHeight =
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(consensus.nSubsidySlowStartInterval / 2) + consensus.nSubsidyHalvingInterval;
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assert(consensus.vFundingPeriods[Consensus::FS_ZECC_SR].valueNumerator <
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].valueDenominator);
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assert(consensus.vFundingPeriods[Consensus::FS_ZECC_SR].startHeight <
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consensus.vFundingPeriods[Consensus::FS_ZECC_SR].endHeight);
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@ -183,6 +199,17 @@ Example implementation
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return params.vFundingPeriods[idx].addresses[addressIndex];
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};
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CAmount FundingStreamValue(
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int nHeight,
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const Consensus::Params& params,
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Consensus::FundingStream idx)
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{
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// Integer division is floor division in C++
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return CAmount((
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GetBlockSubsidy(nHeight, params) * params.vFundingPeriods[idx].valueNumerator
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) / params.vFundingPeriods[idx].valueDenominator);
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}
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std::set<std::pair<CScript, CAmount>> GetActiveFundingStreams(
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int nHeight,
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const Consensus::Params& params)
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@ -195,7 +222,7 @@ Example implementation
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{
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requiredStreams.insert(std::make_pair(
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FundingStreamRecipientAddress(nHeight, params, idx),
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FundingPeriods[idx].value));
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FundingStreamValue(nHeight, params, idx));
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}
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}
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return requiredStreams;
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