[Mining] [ProgPow] Reduce DAG size

src/Makefile.am

@@ -623,6 +623,7 @@ libbitcoin_consensus_a_SOURCES = \
   amount.h \
   arith_uint256.cpp \
   arith_uint256.h \
+  chainparams.cpp \
   consensus/merkle.cpp \
   consensus/merkle.h \
   consensus/params.h \

src/chainparams.cpp

@@ -375,6 +375,7 @@ class CMainParams : public CChainParams {
         nHeightLightZerocoin = 335975;
         nValueBlacklist = (282125 + 60540) * COIN;
         nHeightEnforceBlacklist = 336413;
+        nHeightProgPowDAGSizeReduction = 2100000;
         nPreferredMintsPerBlock = 70; //Miner will not include more than this many mints per block
         nPreferredMintsPerTx = 15; //Do not consider a transaction as standard that includes more than this many mints
 
@@ -552,6 +553,7 @@ class CTestNetParams : public CChainParams {
 
         nHeightLightZerocoin = 9428;
         nHeightEnforceBlacklist = 0;
+        nHeightProgPowDAGSizeReduction = 1125000;
 
         /** RingCT/Stealth **/
         nDefaultRingSize = 11;
@@ -723,6 +725,7 @@ class CDevNetParams : public CChainParams {
 
         nHeightLightZerocoin = 1000;
         nHeightEnforceBlacklist = 0;
+        nHeightProgPowDAGSizeReduction = 1071250;
 
         /** RingCT/Stealth **/
         nDefaultRingSize = 11;
@@ -933,6 +936,41 @@ bool CChainParams::CheckKIenforced(int nSpendHeight) const
     return false;
 }
 
+int CChainParams::GetProgPowEpochNumber(int blockNumber) const
+{
+    int epochLength = blockNumber >= HeightProgPowDAGSizeReduction() ?
+                          ETHASH_EPOCH_LENGTH_750MB_PER_YEAR :
+                          ETHASH_EPOCH_LENGTH;
+
+    if (blockNumber >= HeightProgPowDAGSizeReduction()) {
+        blockNumber -= HeightProgPowDAGSizeReduction();
+    }
+
+    return blockNumber ? blockNumber / epochLength : 0;
+}
+
+std::pair<int, int> CChainParams::GetProgPowNextEpoch(int blockNumber) const {
+    int epochLength = blockNumber >= HeightProgPowDAGSizeReduction() ?
+                          ETHASH_EPOCH_LENGTH_750MB_PER_YEAR :
+                          ETHASH_EPOCH_LENGTH;
+
+    int epochBaseHeight = 0;
+    if (blockNumber >= HeightProgPowDAGSizeReduction()) {
+        epochBaseHeight = HeightProgPowDAGSizeReduction();
+    }
+
+    int currentEpoch = (blockNumber - epochBaseHeight) / epochLength;
+    int currentEpochStart = currentEpoch * epochLength + epochBaseHeight;
+
+    if (blockNumber < HeightProgPowDAGSizeReduction() &&
+        currentEpochStart + epochLength >= HeightProgPowDAGSizeReduction()) {
+        // Next epoch is the transition back to epoch 0
+        return { 0, HeightProgPowDAGSizeReduction() };
+    }
+
+    return { currentEpoch + 1, currentEpochStart + epochLength };
+}
+
 
 std::unique_ptr<CChainParams> CreateChainParams(const std::string& chain)
 {

src/chainparams.h

@@ -146,6 +146,7 @@ class CChainParams
     int HeightCheckDenom() const { return nHeightCheckDenom; }
     int HeightLightZerocoin() const { return nHeightLightZerocoin; }
     int HeightEnforceBlacklist() const { return nHeightEnforceBlacklist; }
+    int HeightProgPowDAGSizeReduction() const { return nHeightProgPowDAGSizeReduction; }
 
     uint32_t PowUpdateTimestamp() const { return nPowUpdateTimestamp; }
     uint64_t KIforkTimestamp() const { return nTimeKIfork; }
@@ -164,6 +165,15 @@ class CChainParams
     bool CheckKIenforced(const CBlockIndex* pindex) const;
     bool CheckKIenforced(int nSpendHeight) const;
 
+    /**
+     * Returns the current epoch number for the specified block number
+     */
+    int GetProgPowEpochNumber(int blockNumber) const;
+    /**
+     * Returns a pair with <next epoch, height of next epoch> for the specified block number
+     */
+    std::pair<int, int> GetProgPowNextEpoch(int blockNumber) const;
+
 
 protected:
     CChainParams() {}
@@ -225,6 +235,7 @@ class CChainParams
     int nHeightCheckDenom;
     int nHeightLightZerocoin;
     int nHeightEnforceBlacklist;
+    int nHeightProgPowDAGSizeReduction;
 
     //Settings that are not chain critical, but should not be edited unless the person changing understands the consequence
     int nMaxHeaderRequestWithoutPoW;

src/crypto/ethash/include/ethash/ethash.h

@@ -27,6 +27,7 @@ extern "C" {
 #define ETHASH_REVISION "23"
 
 #define ETHASH_EPOCH_LENGTH 5525
+#define ETHASH_EPOCH_LENGTH_750MB_PER_YEAR 8175
 #define ETHASH_LIGHT_CACHE_ITEM_SIZE 64
 #define ETHASH_FULL_DATASET_ITEM_SIZE 128
 #define ETHASH_NUM_DATASET_ACCESSES 64

src/crypto/ethash/include/ethash/ethash.hpp

@@ -25,7 +25,6 @@ namespace ethash
 {
 constexpr auto revision = ETHASH_REVISION;
 
-static constexpr int epoch_length = ETHASH_EPOCH_LENGTH;
 static constexpr int light_cache_item_size = ETHASH_LIGHT_CACHE_ITEM_SIZE;
 static constexpr int full_dataset_item_size = ETHASH_FULL_DATASET_ITEM_SIZE;
 static constexpr int num_dataset_accesses = ETHASH_NUM_DATASET_ACCESSES;
@@ -72,9 +71,10 @@ static constexpr auto calculate_epoch_seed = ethash_calculate_epoch_seed;
 
 
 /// Calculates the epoch number out of the block number.
+[[deprecated("Use CChainParams::GetProgPowEpochNumber() instead")]]
 inline constexpr int get_epoch_number(int block_number) noexcept
 {
-    return block_number ? block_number / epoch_length : 0;
+    return block_number ? block_number / ETHASH_EPOCH_LENGTH : 0;
 }
 
 /**

src/hash.cpp

@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <chainparams.h>
 #include <hash.h>
 #include <crypto/common.h>
 #include <crypto/hmac_sha512.h>
@@ -272,7 +273,7 @@ uint256 ProgPowHash(const CBlockHeader& blockHeader, uint256& mix_hash)
     {
         LOCK(cs_context_builder);
         // Get the context from the block height
-        const auto epoch_number = ethash::get_epoch_number(blockHeader.nHeight);
+        const auto epoch_number = Params().GetProgPowEpochNumber(blockHeader.nHeight);
         if (!progpow_context || progpow_context->epoch_number != epoch_number)
             progpow_context = ethash::create_epoch_context(epoch_number);
     }

src/rpc/blockchain.cpp

@@ -211,7 +211,7 @@ UniValue blockToJSON(const CBlock& block, const CBlockIndex* tip, const CBlockIn
     if (block.IsProgPow()) {
         result.pushKV("prog_header_hash", block.GetProgPowHeaderHash().GetHex());
         result.pushKV("prog_header_hex", HexStr(ss.begin(), ss.end()));
-        result.pushKV("epoch_number", ethash::get_epoch_number(block.nHeight));
+        result.pushKV("epoch_number", Params().GetProgPowEpochNumber(block.nHeight));
     }
     if (blockindex->pprev)
         result.pushKV("previousblockhash", blockindex->pprev->GetBlockHash().GetHex());

src/rpc/mining.cpp

@@ -762,13 +762,19 @@ static UniValue getblocktemplate_impl(const std::string &strMode, const UniValue
             if (mapProgPowTemplates.count(lastheader)) {
                 if (pblock->nTime - 60 < mapProgPowTemplates.at(lastheader).nTime) {
                     result.pushKV("pprpcheader", lastheader);
-                    result.pushKV("pprpcepoch", ethash::get_epoch_number(pblock->nHeight));
+                    result.pushKV("pprpcepoch", Params().GetProgPowEpochNumber(pblock->nHeight));
+                    auto nextEpoch = Params().GetProgPowNextEpoch(pblock->nHeight);
+                    result.pushKV("pprpcnextepoch", nextEpoch.first);
+                    result.pushKV("pprpcnextepochheight", nextEpoch.second);
                     return result;
                 }
             }
 
             result.pushKV("pprpcheader", pblock->GetProgPowHeaderHash().GetHex());
-            result.pushKV("pprpcepoch", progpow::get_epoch_number(pblock->nHeight));
+            result.pushKV("pprpcepoch", Params().GetProgPowEpochNumber(pblock->nHeight));
+            auto nextEpoch = Params().GetProgPowNextEpoch(pblock->nHeight);
+            result.pushKV("pprpcnextepoch", nextEpoch.first);
+            result.pushKV("pprpcnextepochheight", nextEpoch.second);
             mapProgPowTemplates[pblock->GetProgPowHeaderHash().GetHex()] = *pblock;
             lastheader = pblock->GetProgPowHeaderHash().GetHex();
         }