Merge #9239: Disable fee estimates for 1 block target

e878689 Make GUI incapable of setting tx confirm target of 1 (Alex Morcos)
d824ad0 Disable fee estimates for a confirm target of 1 block (Alex Morcos)

src/policy/fees.cpp

@@ -404,7 +404,8 @@ void CBlockPolicyEstimator::processBlock(unsigned int nBlockHeight,
 CFeeRate CBlockPolicyEstimator::estimateFee(int confTarget)
 {
     // Return failure if trying to analyze a target we're not tracking
-    if (confTarget <= 0 || (unsigned int)confTarget > feeStats.GetMaxConfirms())
+    // It's not possible to get reasonable estimates for confTarget of 1
+    if (confTarget <= 1 || (unsigned int)confTarget > feeStats.GetMaxConfirms())
         return CFeeRate(0);
 
     double median = feeStats.EstimateMedianVal(confTarget, SUFFICIENT_FEETXS, MIN_SUCCESS_PCT, true, nBestSeenHeight);
@@ -423,6 +424,10 @@ CFeeRate CBlockPolicyEstimator::estimateSmartFee(int confTarget, int *answerFoun
     if (confTarget <= 0 || (unsigned int)confTarget > feeStats.GetMaxConfirms())
         return CFeeRate(0);
 
+    // It's not possible to get reasonable estimates for confTarget of 1
+    if (confTarget == 1)
+        confTarget = 2;
+
     double median = -1;
     while (median < 0 && (unsigned int)confTarget <= feeStats.GetMaxConfirms()) {
         median = feeStats.EstimateMedianVal(confTarget++, SUFFICIENT_FEETXS, MIN_SUCCESS_PCT, true, nBestSeenHeight);

src/qt/forms/sendcoinsdialog.ui

@@ -1064,7 +1064,7 @@
                       <number>0</number>
                      </property>
                      <property name="maximum">
-                      <number>24</number>
+                      <number>23</number>
                      </property>
                      <property name="pageStep">
                       <number>1</number>

src/qt/sendcoinsdialog.cpp

@@ -175,7 +175,7 @@ void SendCoinsDialog::setModel(WalletModel *_model)
         // set the smartfee-sliders default value (wallets default conf.target or last stored value)
         QSettings settings;
         if (settings.value("nSmartFeeSliderPosition").toInt() == 0)
-            ui->sliderSmartFee->setValue(ui->sliderSmartFee->maximum() - model->getDefaultConfirmTarget() + 1);
+            ui->sliderSmartFee->setValue(ui->sliderSmartFee->maximum() - model->getDefaultConfirmTarget() + 2);
         else
             ui->sliderSmartFee->setValue(settings.value("nSmartFeeSliderPosition").toInt());
     }
@@ -241,7 +241,7 @@ void SendCoinsDialog::on_sendButton_clicked()
     if (model->getOptionsModel()->getCoinControlFeatures())
         ctrl = *CoinControlDialog::coinControl;
     if (ui->radioSmartFee->isChecked())
-        ctrl.nConfirmTarget = ui->sliderSmartFee->maximum() - ui->sliderSmartFee->value() + 1;
+        ctrl.nConfirmTarget = ui->sliderSmartFee->maximum() - ui->sliderSmartFee->value() + 2;
     else
         ctrl.nConfirmTarget = 0;
 
@@ -601,7 +601,7 @@ void SendCoinsDialog::updateGlobalFeeVariables()
 {
     if (ui->radioSmartFee->isChecked())
     {
-        int nConfirmTarget = ui->sliderSmartFee->maximum() - ui->sliderSmartFee->value() + 1;
+        int nConfirmTarget = ui->sliderSmartFee->maximum() - ui->sliderSmartFee->value() + 2;
         payTxFee = CFeeRate(0);
 
         // set nMinimumTotalFee to 0 to not accidentally pay a custom fee
@@ -646,7 +646,7 @@ void SendCoinsDialog::updateSmartFeeLabel()
     if(!model || !model->getOptionsModel())
         return;
 
-    int nBlocksToConfirm = ui->sliderSmartFee->maximum() - ui->sliderSmartFee->value() + 1;
+    int nBlocksToConfirm = ui->sliderSmartFee->maximum() - ui->sliderSmartFee->value() + 2;
     int estimateFoundAtBlocks = nBlocksToConfirm;
     CFeeRate feeRate = mempool.estimateSmartFee(nBlocksToConfirm, &estimateFoundAtBlocks);
     if (feeRate <= CFeeRate(0)) // not enough data => minfee

src/rpc/mining.cpp

@@ -785,6 +785,8 @@ UniValue estimatefee(const JSONRPCRequest& request)
             "\n"
             "A negative value is returned if not enough transactions and blocks\n"
             "have been observed to make an estimate.\n"
+            "-1 is always returned for nblocks == 1 as it is impossible to calculate\n"
+            "a fee that is high enough to get reliably included in the next block.\n"
             "\nExample:\n"
             + HelpExampleCli("estimatefee", "6")
             );

src/test/policyestimator_tests.cpp

@@ -95,17 +95,22 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
     // Highest feerate is 10*baseRate and gets in all blocks,
     // second highest feerate is 9*baseRate and gets in 9/10 blocks = 90%,
     // third highest feerate is 8*base rate, and gets in 8/10 blocks = 80%,
-    // so estimateFee(1) should return 10*baseRate.
+    // so estimateFee(1) would return 10*baseRate but is hardcoded to return failure
     // Second highest feerate has 100% chance of being included by 2 blocks,
     // so estimateFee(2) should return 9*baseRate etc...
     for (int i = 1; i < 10;i++) {
         origFeeEst.push_back(mpool.estimateFee(i).GetFeePerK());
-        if (i > 1) { // Fee estimates should be monotonically decreasing
+        if (i > 2) { // Fee estimates should be monotonically decreasing
             BOOST_CHECK(origFeeEst[i-1] <= origFeeEst[i-2]);
         }
         int mult = 11-i;
-        BOOST_CHECK(origFeeEst[i-1] < mult*baseRate.GetFeePerK() + deltaFee);
-        BOOST_CHECK(origFeeEst[i-1] > mult*baseRate.GetFeePerK() - deltaFee);
+        if (i > 1) {
+            BOOST_CHECK(origFeeEst[i-1] < mult*baseRate.GetFeePerK() + deltaFee);
+            BOOST_CHECK(origFeeEst[i-1] > mult*baseRate.GetFeePerK() - deltaFee);
+        }
+        else {
+            BOOST_CHECK(origFeeEst[i-1] == CFeeRate(0).GetFeePerK());
+        }
     }
 
     // Mine 50 more blocks with no transactions happening, estimates shouldn't change
@@ -113,7 +118,8 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
     while (blocknum < 250)
         mpool.removeForBlock(block, ++blocknum);
 
-    for (int i = 1; i < 10;i++) {
+    BOOST_CHECK(mpool.estimateFee(1) == CFeeRate(0));
+    for (int i = 2; i < 10;i++) {
         BOOST_CHECK(mpool.estimateFee(i).GetFeePerK() < origFeeEst[i-1] + deltaFee);
         BOOST_CHECK(mpool.estimateFee(i).GetFeePerK() > origFeeEst[i-1] - deltaFee);
     }
@@ -151,7 +157,8 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
     }
     mpool.removeForBlock(block, 265);
     block.clear();
-    for (int i = 1; i < 10;i++) {
+    BOOST_CHECK(mpool.estimateFee(1) == CFeeRate(0));
+    for (int i = 2; i < 10;i++) {
         BOOST_CHECK(mpool.estimateFee(i).GetFeePerK() > origFeeEst[i-1] - deltaFee);
     }
 
@@ -172,7 +179,8 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
         mpool.removeForBlock(block, ++blocknum);
         block.clear();
     }
-    for (int i = 1; i < 10; i++) {
+    BOOST_CHECK(mpool.estimateFee(1) == CFeeRate(0));
+    for (int i = 2; i < 10; i++) {
         BOOST_CHECK(mpool.estimateFee(i).GetFeePerK() < origFeeEst[i-1] - deltaFee);
     }