Merge pull request #5 from sunnyking/master

FeatherCoin Difficulty Protocol Upgrade
FeatherCoin · May 15, 2013 · bdcaf32 · bdcaf32
2 parents 3458672 + 1f97245
commit bdcaf32
Showing 1 changed file with 25 additions and 15 deletions.
diff --git a/src/main.cpp b/src/main.cpp
@@ -835,9 +835,8 @@ int64 static GetBlockValue(int nHeight, int64 nFees)
     return nSubsidy + nFees;
 }
 
-static const int64 nTargetTimespan = 3.5 * 24 * 60 * 60; // Feathercoin: 3.5 days
+static const int64 nTargetTimespan = (7 * 24 * 60 * 60) / 8; // Feathercoin: 7/8 days
 static const int64 nTargetSpacing = 2.5 * 60; // Feathercoin: 2.5 minutes
-static const int64 nInterval = nTargetTimespan / nTargetSpacing;
 
 //
 // minimum amount of work that could possibly be required nTime after
@@ -854,8 +853,8 @@ unsigned int ComputeMinWork(unsigned int nBase, int64 nTime)
     bnResult.SetCompact(nBase);
     while (nTime > 0 && bnResult < bnProofOfWorkLimit)
     {
-        // Maximum 400% adjustment...
-        bnResult *= 4;
+        // Maximum 141% adjustment...
+        bnResult = (bnResult * 99) / 70;
         // ... in best-case exactly 4-times-normal target time
         nTime -= nTargetTimespan*4;
     }
@@ -872,8 +871,17 @@ unsigned int static GetNextWorkRequired(const CBlockIndex* pindexLast, const CBl
     if (pindexLast == NULL)
         return nProofOfWorkLimit;
 
-    // Only change once per interval
-    if ((pindexLast->nHeight+1) % nInterval != 0)
+    // FeatherCoin difficulty adjustment protocol switch
+    static const int nDifficultySwitchHeight = 33000;
+    int nHeight = pindexLast->nHeight + 1;
+    bool fNewDifficultyProtocol = (nHeight >= nDifficultySwitchHeight || fTestNet);
+
+    int64 nTargetTimespanCurrent = fNewDifficultyProtocol? nTargetTimespan : (nTargetTimespan*4);
+    int64 nInterval = nTargetTimespanCurrent / nTargetSpacing;
+
+    // Only change once per interval, or at protocol switch height
+    if ((nHeight % nInterval != 0) &&
+        (nHeight != nDifficultySwitchHeight || fTestNet))
     {
         // Special difficulty rule for testnet:
         if (fTestNet)
@@ -898,35 +906,37 @@ unsigned int static GetNextWorkRequired(const CBlockIndex* pindexLast, const CBl
     // Feathercoin: This fixes an issue where a 51% attack can change difficulty at will.
     // Go back the full period unless it's the first retarget after genesis. Code courtesy of Art Forz
     int blockstogoback = nInterval-1;
-    if ((pindexLast->nHeight+1) != nInterval)
+    if (nHeight != nInterval)
         blockstogoback = nInterval;
 
-    // Go back by what we want to be 14 days worth of blocks
+    // Go back by what we want to be 7/8 days worth of blocks
     const CBlockIndex* pindexFirst = pindexLast;
     for (int i = 0; pindexFirst && i < blockstogoback; i++)
         pindexFirst = pindexFirst->pprev;
     assert(pindexFirst);
 
-    // Limit adjustment step
+    // Limit adjustment step to 141% (400% before protocol switch)
     int64 nActualTimespan = pindexLast->GetBlockTime() - pindexFirst->GetBlockTime();
     printf("  nActualTimespan = %"PRI64d"  before bounds\n", nActualTimespan);
-    if (nActualTimespan < nTargetTimespan/4)
-        nActualTimespan = nTargetTimespan/4;
-    if (nActualTimespan > nTargetTimespan*4)
-        nActualTimespan = nTargetTimespan*4;
+    int64 nActualTimespanMax = fNewDifficultyProtocol? ((nTargetTimespanCurrent*99)/70) : (nTargetTimespanCurrent*4);
+    int64 nActualTimespanMin = fNewDifficultyProtocol? ((nTargetTimespanCurrent*70)/99) : (nTargetTimespanCurrent/4);
+    if (nActualTimespan < nActualTimespanMin)
+        nActualTimespan = nActualTimespanMin;
+    if (nActualTimespan > nActualTimespanMax)
+        nActualTimespan = nActualTimespanMax;
 
     // Retarget
     CBigNum bnNew;
     bnNew.SetCompact(pindexLast->nBits);
     bnNew *= nActualTimespan;
-    bnNew /= nTargetTimespan;
+    bnNew /= nTargetTimespanCurrent;
 
     if (bnNew > bnProofOfWorkLimit)
         bnNew = bnProofOfWorkLimit;
 
     /// debug print
     printf("GetNextWorkRequired RETARGET\n");
-    printf("nTargetTimespan = %"PRI64d"    nActualTimespan = %"PRI64d"\n", nTargetTimespan, nActualTimespan);
+    printf("nTargetTimespan = %"PRI64d"    nActualTimespan = %"PRI64d"\n", nTargetTimespanCurrent, nActualTimespan);
     printf("Before: %08x  %s\n", pindexLast->nBits, CBigNum().SetCompact(pindexLast->nBits).getuint256().ToString().c_str());
     printf("After:  %08x  %s\n", bnNew.GetCompact(), bnNew.getuint256().ToString().c_str());