Add smart fee estimation functions

These are more useful fee and priority estimation functions. If there is no fee/pri high enough for the target you are aiming for, it will give you the estimate for the lowest target that you can reliably obtain.  This is better than defaulting to the minimum.  It will also pass back the target for which it returned an answer.

src/policy/fees.cpp

@@ -504,6 +504,28 @@ CFeeRate CBlockPolicyEstimator::estimateFee(int confTarget)
     return CFeeRate(median);
 }
 
+CFeeRate CBlockPolicyEstimator::estimateSmartFee(int confTarget, int *answerFoundAtTarget)
+{
+    if (answerFoundAtTarget)
+        *answerFoundAtTarget = confTarget;
+    // Return failure if trying to analyze a target we're not tracking
+    if (confTarget <= 0 || (unsigned int)confTarget > feeStats.GetMaxConfirms())
+        return CFeeRate(0);
+
+    double median = -1;
+    while (median < 0 && (unsigned int)confTarget <= feeStats.GetMaxConfirms()) {
+        median = feeStats.EstimateMedianVal(confTarget++, SUFFICIENT_FEETXS, MIN_SUCCESS_PCT, true, nBestSeenHeight);
+    }
+
+    if (answerFoundAtTarget)
+        *answerFoundAtTarget = confTarget - 1;
+
+    if (median < 0)
+        return CFeeRate(0);
+
+    return CFeeRate(median);
+}
+
 double CBlockPolicyEstimator::estimatePriority(int confTarget)
 {
     // Return failure if trying to analyze a target we're not tracking
@@ -513,6 +535,25 @@ double CBlockPolicyEstimator::estimatePriority(int confTarget)
     return priStats.EstimateMedianVal(confTarget, SUFFICIENT_PRITXS, MIN_SUCCESS_PCT, true, nBestSeenHeight);
 }
 
+double CBlockPolicyEstimator::estimateSmartPriority(int confTarget, int *answerFoundAtTarget)
+{
+    if (answerFoundAtTarget)
+        *answerFoundAtTarget = confTarget;
+    // Return failure if trying to analyze a target we're not tracking
+    if (confTarget <= 0 || (unsigned int)confTarget > priStats.GetMaxConfirms())
+        return -1;
+
+    double median = -1;
+    while (median < 0 && (unsigned int)confTarget <= priStats.GetMaxConfirms()) {
+        median = priStats.EstimateMedianVal(confTarget++, SUFFICIENT_PRITXS, MIN_SUCCESS_PCT, true, nBestSeenHeight);
+    }
+
+    if (answerFoundAtTarget)
+        *answerFoundAtTarget = confTarget - 1;
+
+    return median;
+}
+
 void CBlockPolicyEstimator::Write(CAutoFile& fileout)
 {
     fileout << nBestSeenHeight;

src/policy/fees.h

@@ -242,9 +242,21 @@ public:
     /** Return a fee estimate */
     CFeeRate estimateFee(int confTarget);
 
+    /** Estimate fee rate needed to get be included in a block within
+     *  confTarget blocks. If no answer can be given at confTarget, return an
+     *  estimate at the lowest target where one can be given.
+     */
+    CFeeRate estimateSmartFee(int confTarget, int *answerFoundAtTarget);
+
     /** Return a priority estimate */
     double estimatePriority(int confTarget);
 
+    /** Estimate priority needed to get be included in a block within
+     *  confTarget blocks. If no answer can be given at confTarget, return an
+     *  estimate at the lowest target where one can be given.
+     */
+    double estimateSmartPriority(int confTarget, int *answerFoundAtTarget);
+
     /** Write estimation data to a file */
     void Write(CAutoFile& fileout);
 

src/txmempool.cpp

@@ -701,11 +701,21 @@ CFeeRate CTxMemPool::estimateFee(int nBlocks) const
     LOCK(cs);
     return minerPolicyEstimator->estimateFee(nBlocks);
 }
+CFeeRate CTxMemPool::estimateSmartFee(int nBlocks, int *answerFoundAtBlocks) const
+{
+    LOCK(cs);
+    return minerPolicyEstimator->estimateSmartFee(nBlocks, answerFoundAtBlocks);
+}
 double CTxMemPool::estimatePriority(int nBlocks) const
 {
     LOCK(cs);
     return minerPolicyEstimator->estimatePriority(nBlocks);
 }
+double CTxMemPool::estimateSmartPriority(int nBlocks, int *answerFoundAtBlocks) const
+{
+    LOCK(cs);
+    return minerPolicyEstimator->estimateSmartPriority(nBlocks, answerFoundAtBlocks);
+}
 
 bool
 CTxMemPool::WriteFeeEstimates(CAutoFile& fileout) const

src/txmempool.h

@@ -454,9 +454,21 @@ public:
 
     bool lookup(uint256 hash, CTransaction& result) const;
 
+    /** Estimate fee rate needed to get into the next nBlocks
+     *  If no answer can be given at nBlocks, return an estimate
+     *  at the lowest number of blocks where one can be given
+     */
+    CFeeRate estimateSmartFee(int nBlocks, int *answerFoundAtBlocks = NULL) const;
+
     /** Estimate fee rate needed to get into the next nBlocks */
     CFeeRate estimateFee(int nBlocks) const;
 
+    /** Estimate priority needed to get into the next nBlocks
+     *  If no answer can be given at nBlocks, return an estimate
+     *  at the lowest number of blocks where one can be given
+     */
+    double estimateSmartPriority(int nBlocks, int *answerFoundAtBlocks = NULL) const;
+
     /** Estimate priority needed to get into the next nBlocks */
     double estimatePriority(int nBlocks) const;