From ae2f68d655808d6070af015eb02f33d3de727314 Mon Sep 17 00:00:00 2001
From: UdjinM6 <UdjinM6@users.noreply.github.com>
Date: Thu, 31 Oct 2019 21:52:17 +0300
Subject: [PATCH 1/3] From 2 best sets with the same `nTotal` in
 ApproximateBestSubset prefer the one with less inputs

---
 src/wallet/wallet.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 38d827e0c348..e4708347e94c 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2863,6 +2863,7 @@ static void ApproximateBestSubset(const std::vector<CInputCoin>& vValue, const C
 
     vfBest.assign(vValue.size(), true);
     nBest = nTotalLower;
+    int nBestCount = 0;
 
     FastRandomContext insecure_rand;
 
@@ -2870,6 +2871,7 @@ static void ApproximateBestSubset(const std::vector<CInputCoin>& vValue, const C
     {
         vfIncluded.assign(vValue.size(), false);
         CAmount nTotal = 0;
+        int nTotalCount = 0;
         bool fReachedTarget = false;
         for (int nPass = 0; nPass < 2 && !fReachedTarget; nPass++)
         {
@@ -2884,16 +2886,19 @@ static void ApproximateBestSubset(const std::vector<CInputCoin>& vValue, const C
                 if (nPass == 0 ? insecure_rand.randbool() : !vfIncluded[i])
                 {
                     nTotal += vValue[i].txout.nValue;
+                    ++nTotalCount;
                     vfIncluded[i] = true;
                     if (nTotal >= nTargetValue)
                     {
                         fReachedTarget = true;
-                        if (nTotal < nBest)
+                        if (nTotal < nBest || (nTotal == nBest && nTotalCount < nBestCount))
                         {
                             nBest = nTotal;
+                            nBestCount = nTotalCount;
                             vfBest = vfIncluded;
                         }
                         nTotal -= vValue[i].txout.nValue;
+                        --nTotalCount;
                         vfIncluded[i] = false;
                     }
                 }

From 5d89b84ee5a49d49a6374d17a4ae88430593f732 Mon Sep 17 00:00:00 2001
From: UdjinM6 <UdjinM6@users.noreply.github.com>
Date: Thu, 31 Oct 2019 21:54:47 +0300
Subject: [PATCH 2/3] There is no reason to run ApproximateBestSubset again if
 nMinChange is 0

---
 src/wallet/wallet.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index e4708347e94c..5308162fcc39 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -3052,7 +3052,7 @@ bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, const int nConfMin
     CAmount nBest;
 
     ApproximateBestSubset(vValue, nTotalLower, nTargetValue, vfBest, nBest);
-    if (nBest != nTargetValue && nTotalLower >= nTargetValue + nMinChange)
+    if (nBest != nTargetValue && nMinChange != 0 && nTotalLower >= nTargetValue + nMinChange)
         ApproximateBestSubset(vValue, nTotalLower, nTargetValue + nMinChange, vfBest, nBest);
 
     // If we have a bigger coin and (either the stochastic approximation didn't find a good solution,

From e06f5a6c0d7aa21ae36a24e428be9daffc2c54fc Mon Sep 17 00:00:00 2001
From: UdjinM6 <UdjinM6@users.noreply.github.com>
Date: Mon, 4 Nov 2019 14:01:32 +0300
Subject: [PATCH 3/3] Apply review suggestions

---
 src/wallet/wallet.cpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 5308162fcc39..95db20386183 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2863,7 +2863,7 @@ static void ApproximateBestSubset(const std::vector<CInputCoin>& vValue, const C
 
     vfBest.assign(vValue.size(), true);
     nBest = nTotalLower;
-    int nBestCount = 0;
+    int nBestInputCount = 0;
 
     FastRandomContext insecure_rand;
 
@@ -2871,7 +2871,7 @@ static void ApproximateBestSubset(const std::vector<CInputCoin>& vValue, const C
     {
         vfIncluded.assign(vValue.size(), false);
         CAmount nTotal = 0;
-        int nTotalCount = 0;
+        int nTotalInputCount = 0;
         bool fReachedTarget = false;
         for (int nPass = 0; nPass < 2 && !fReachedTarget; nPass++)
         {
@@ -2886,19 +2886,19 @@ static void ApproximateBestSubset(const std::vector<CInputCoin>& vValue, const C
                 if (nPass == 0 ? insecure_rand.randbool() : !vfIncluded[i])
                 {
                     nTotal += vValue[i].txout.nValue;
-                    ++nTotalCount;
+                    ++nTotalInputCount;
                     vfIncluded[i] = true;
                     if (nTotal >= nTargetValue)
                     {
                         fReachedTarget = true;
-                        if (nTotal < nBest || (nTotal == nBest && nTotalCount < nBestCount))
+                        if (nTotal < nBest || (nTotal == nBest && nTotalInputCount < nBestInputCount))
                         {
                             nBest = nTotal;
-                            nBestCount = nTotalCount;
+                            nBestInputCount = nTotalInputCount;
                             vfBest = vfIncluded;
                         }
                         nTotal -= vValue[i].txout.nValue;
-                        --nTotalCount;
+                        --nTotalInputCount;
                         vfIncluded[i] = false;
                     }
                 }