refactor coin selection for parameterizable change target

no behavior changes, since the target is always MIN_CHANGE

1 files changed, 74 insertions, 71 deletions

diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp
index 14bec8ca4c..87ce18c8c9 100644
--- a/src/wallet/test/coinselector_tests.cpp
+++ b/src/wallet/test/coinselector_tests.cpp
@@ -150,6 +150,7 @@ inline std::vector<OutputGroup>& KnapsackGroupOutputs(const std::vector<COutput>
         rand,
         /* change_output_size= */ 0,
         /* change_spend_size= */ 0,
+        /*min_change_target=*/ CENT,
         /* effective_feerate= */ CFeeRate(0),
         /* long_term_feerate= */ CFeeRate(0),
         /* discard_feerate= */ CFeeRate(0),
@@ -294,6 +295,7 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         rand,
         /* change_output_size= */ 0,
         /* change_spend_size= */ 0,
+        /*min_change_target=*/ 0,
         /* effective_feerate= */ CFeeRate(3000),
         /* long_term_feerate= */ CFeeRate(1000),
         /* discard_feerate= */ CFeeRate(1000),
@@ -347,7 +349,7 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
 BOOST_AUTO_TEST_CASE(knapsack_solver_test)
 {
     FastRandomContext rand{};
-    const auto temp1{[&rand](std::vector<OutputGroup>& g, const CAmount& v) { return KnapsackSolver(g, v, rand); }};
+    const auto temp1{[&rand](std::vector<OutputGroup>& g, const CAmount& v, CAmount c) { return KnapsackSolver(g, v, c, rand); }};
     const auto KnapsackSolver{temp1};
     std::unique_ptr<CWallet> wallet = std::make_unique<CWallet>(m_node.chain.get(), "", m_args, CreateMockWalletDatabase());
     wallet->LoadWallet();
@@ -363,25 +365,25 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         coins.clear();
 
         // with an empty wallet we can't even pay one cent
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1 * CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1 * CENT, CENT));
 
         add_coin(coins, *wallet, 1*CENT, 4);        // add a new 1 cent coin
 
         // with a new 1 cent coin, we still can't find a mature 1 cent
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1 * CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1 * CENT, CENT));
 
         // but we can find a new 1 cent
-        const auto result1 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT);
+        const auto result1 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result1);
         BOOST_CHECK_EQUAL(result1->GetSelectedValue(), 1 * CENT);
 
         add_coin(coins, *wallet, 2*CENT);           // add a mature 2 cent coin
 
         // we can't make 3 cents of mature coins
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 3 * CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 3 * CENT, CENT));
 
         // we can make 3 cents of new coins
-        const auto result2 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 3 * CENT);
+        const auto result2 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 3 * CENT, CENT);
         BOOST_CHECK(result2);
         BOOST_CHECK_EQUAL(result2->GetSelectedValue(), 3 * CENT);
 
@@ -392,38 +394,38 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         // now we have new: 1+10=11 (of which 10 was self-sent), and mature: 2+5+20=27.  total = 38
 
         // we can't make 38 cents only if we disallow new coins:
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 38 * CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 38 * CENT, CENT));
         // we can't even make 37 cents if we don't allow new coins even if they're from us
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard_extra), 38 * CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard_extra), 38 * CENT, CENT));
         // but we can make 37 cents if we accept new coins from ourself
-        const auto result3 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 37 * CENT);
+        const auto result3 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 37 * CENT, CENT);
         BOOST_CHECK(result3);
         BOOST_CHECK_EQUAL(result3->GetSelectedValue(), 37 * CENT);
         // and we can make 38 cents if we accept all new coins
-        const auto result4 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 38 * CENT);
+        const auto result4 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 38 * CENT, CENT);
         BOOST_CHECK(result4);
         BOOST_CHECK_EQUAL(result4->GetSelectedValue(), 38 * CENT);
 
         // try making 34 cents from 1,2,5,10,20 - we can't do it exactly
-        const auto result5 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 34 * CENT);
+        const auto result5 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 34 * CENT, CENT);
         BOOST_CHECK(result5);
         BOOST_CHECK_EQUAL(result5->GetSelectedValue(), 35 * CENT);       // but 35 cents is closest
         BOOST_CHECK_EQUAL(result5->GetInputSet().size(), 3U);     // the best should be 20+10+5.  it's incredibly unlikely the 1 or 2 got included (but possible)
 
         // when we try making 7 cents, the smaller coins (1,2,5) are enough.  We should see just 2+5
-        const auto result6 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 7 * CENT);
+        const auto result6 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 7 * CENT, CENT);
         BOOST_CHECK(result6);
         BOOST_CHECK_EQUAL(result6->GetSelectedValue(), 7 * CENT);
         BOOST_CHECK_EQUAL(result6->GetInputSet().size(), 2U);
 
         // when we try making 8 cents, the smaller coins (1,2,5) are exactly enough.
-        const auto result7 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 8 * CENT);
+        const auto result7 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 8 * CENT, CENT);
         BOOST_CHECK(result7);
         BOOST_CHECK(result7->GetSelectedValue() == 8 * CENT);
         BOOST_CHECK_EQUAL(result7->GetInputSet().size(), 3U);
 
         // when we try making 9 cents, no subset of smaller coins is enough, and we get the next bigger coin (10)
-        const auto result8 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 9 * CENT);
+        const auto result8 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 9 * CENT, CENT);
         BOOST_CHECK(result8);
         BOOST_CHECK_EQUAL(result8->GetSelectedValue(), 10 * CENT);
         BOOST_CHECK_EQUAL(result8->GetInputSet().size(), 1U);
@@ -438,12 +440,12 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(coins, *wallet, 30*CENT); // now we have 6+7+8+20+30 = 71 cents total
 
         // check that we have 71 and not 72
-        const auto result9 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 71 * CENT);
+        const auto result9 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 71 * CENT, CENT);
         BOOST_CHECK(result9);
-        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 72 * CENT));
+        BOOST_CHECK(!KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 72 * CENT, CENT));
 
         // now try making 16 cents.  the best smaller coins can do is 6+7+8 = 21; not as good at the next biggest coin, 20
-        const auto result10 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT);
+        const auto result10 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT, CENT);
         BOOST_CHECK(result10);
         BOOST_CHECK_EQUAL(result10->GetSelectedValue(), 20 * CENT); // we should get 20 in one coin
         BOOST_CHECK_EQUAL(result10->GetInputSet().size(), 1U);
@@ -451,7 +453,7 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(coins, *wallet,  5*CENT); // now we have 5+6+7+8+20+30 = 75 cents total
 
         // now if we try making 16 cents again, the smaller coins can make 5+6+7 = 18 cents, better than the next biggest coin, 20
-        const auto result11 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT);
+        const auto result11 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT, CENT);
         BOOST_CHECK(result11);
         BOOST_CHECK_EQUAL(result11->GetSelectedValue(), 18 * CENT); // we should get 18 in 3 coins
         BOOST_CHECK_EQUAL(result11->GetInputSet().size(), 3U);
@@ -459,13 +461,13 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(coins, *wallet,  18*CENT); // now we have 5+6+7+8+18+20+30
 
         // and now if we try making 16 cents again, the smaller coins can make 5+6+7 = 18 cents, the same as the next biggest coin, 18
-        const auto result12 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT);
+        const auto result12 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 16 * CENT, CENT);
         BOOST_CHECK(result12);
         BOOST_CHECK_EQUAL(result12->GetSelectedValue(), 18 * CENT);  // we should get 18 in 1 coin
         BOOST_CHECK_EQUAL(result12->GetInputSet().size(), 1U); // because in the event of a tie, the biggest coin wins
 
         // now try making 11 cents.  we should get 5+6
-        const auto result13 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 11 * CENT);
+        const auto result13 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 11 * CENT, CENT);
         BOOST_CHECK(result13);
         BOOST_CHECK_EQUAL(result13->GetSelectedValue(), 11 * CENT);
         BOOST_CHECK_EQUAL(result13->GetInputSet().size(), 2U);
@@ -475,12 +477,12 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         add_coin(coins, *wallet,  2*COIN);
         add_coin(coins, *wallet,  3*COIN);
         add_coin(coins, *wallet,  4*COIN); // now we have 5+6+7+8+18+20+30+100+200+300+400 = 1094 cents
-        const auto result14 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 95 * CENT);
+        const auto result14 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 95 * CENT, CENT);
         BOOST_CHECK(result14);
         BOOST_CHECK_EQUAL(result14->GetSelectedValue(), 1 * COIN);  // we should get 1 BTC in 1 coin
         BOOST_CHECK_EQUAL(result14->GetInputSet().size(), 1U);
 
-        const auto result15 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 195 * CENT);
+        const auto result15 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 195 * CENT, CENT);
         BOOST_CHECK(result15);
         BOOST_CHECK_EQUAL(result15->GetSelectedValue(), 2 * COIN);  // we should get 2 BTC in 1 coin
         BOOST_CHECK_EQUAL(result15->GetInputSet().size(), 1U);
@@ -488,34 +490,34 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         // empty the wallet and start again, now with fractions of a cent, to test small change avoidance
 
         coins.clear();
-        add_coin(coins, *wallet, MIN_CHANGE * 1 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 2 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 3 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 4 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 5 / 10);
-
-        // try making 1 * MIN_CHANGE from the 1.5 * MIN_CHANGE
-        // we'll get change smaller than MIN_CHANGE whatever happens, so can expect MIN_CHANGE exactly
-        const auto result16 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), MIN_CHANGE);
+        add_coin(coins, *wallet, CENT * 1 / 10);
+        add_coin(coins, *wallet, CENT * 2 / 10);
+        add_coin(coins, *wallet, CENT * 3 / 10);
+        add_coin(coins, *wallet, CENT * 4 / 10);
+        add_coin(coins, *wallet, CENT * 5 / 10);
+
+        // try making 1 * CENT from the 1.5 * CENT
+        // we'll get change smaller than CENT whatever happens, so can expect CENT exactly
+        const auto result16 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT, CENT);
         BOOST_CHECK(result16);
-        BOOST_CHECK_EQUAL(result16->GetSelectedValue(), MIN_CHANGE);
+        BOOST_CHECK_EQUAL(result16->GetSelectedValue(), CENT);
 
         // but if we add a bigger coin, small change is avoided
-        add_coin(coins, *wallet, 1111*MIN_CHANGE);
+        add_coin(coins, *wallet, 1111*CENT);
 
         // try making 1 from 0.1 + 0.2 + 0.3 + 0.4 + 0.5 + 1111 = 1112.5
-        const auto result17 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * MIN_CHANGE);
+        const auto result17 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result17);
-        BOOST_CHECK_EQUAL(result17->GetSelectedValue(), 1 * MIN_CHANGE); // we should get the exact amount
+        BOOST_CHECK_EQUAL(result17->GetSelectedValue(), 1 * CENT); // we should get the exact amount
 
         // if we add more small coins:
-        add_coin(coins, *wallet, MIN_CHANGE * 6 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 7 / 10);
+        add_coin(coins, *wallet, CENT * 6 / 10);
+        add_coin(coins, *wallet, CENT * 7 / 10);
 
-        // and try again to make 1.0 * MIN_CHANGE
-        const auto result18 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * MIN_CHANGE);
+        // and try again to make 1.0 * CENT
+        const auto result18 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result18);
-        BOOST_CHECK_EQUAL(result18->GetSelectedValue(), 1 * MIN_CHANGE); // we should get the exact amount
+        BOOST_CHECK_EQUAL(result18->GetSelectedValue(), 1 * CENT); // we should get the exact amount
 
         // run the 'mtgox' test (see https://blockexplorer.com/tx/29a3efd3ef04f9153d47a990bd7b048a4b2d213daaa5fb8ed670fb85f13bdbcf)
         // they tried to consolidate 10 50k coins into one 500k coin, and ended up with 50k in change
@@ -523,52 +525,52 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         for (int j = 0; j < 20; j++)
             add_coin(coins, *wallet, 50000 * COIN);
 
-        const auto result19 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 500000 * COIN);
+        const auto result19 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 500000 * COIN, CENT);
         BOOST_CHECK(result19);
         BOOST_CHECK_EQUAL(result19->GetSelectedValue(), 500000 * COIN); // we should get the exact amount
         BOOST_CHECK_EQUAL(result19->GetInputSet().size(), 10U); // in ten coins
 
-        // if there's not enough in the smaller coins to make at least 1 * MIN_CHANGE change (0.5+0.6+0.7 < 1.0+1.0),
+        // if there's not enough in the smaller coins to make at least 1 * CENT change (0.5+0.6+0.7 < 1.0+1.0),
         // we need to try finding an exact subset anyway
 
         // sometimes it will fail, and so we use the next biggest coin:
         coins.clear();
-        add_coin(coins, *wallet, MIN_CHANGE * 5 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 6 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 7 / 10);
-        add_coin(coins, *wallet, 1111 * MIN_CHANGE);
-        const auto result20 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * MIN_CHANGE);
+        add_coin(coins, *wallet, CENT * 5 / 10);
+        add_coin(coins, *wallet, CENT * 6 / 10);
+        add_coin(coins, *wallet, CENT * 7 / 10);
+        add_coin(coins, *wallet, 1111 * CENT);
+        const auto result20 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 1 * CENT, CENT);
         BOOST_CHECK(result20);
-        BOOST_CHECK_EQUAL(result20->GetSelectedValue(), 1111 * MIN_CHANGE); // we get the bigger coin
+        BOOST_CHECK_EQUAL(result20->GetSelectedValue(), 1111 * CENT); // we get the bigger coin
         BOOST_CHECK_EQUAL(result20->GetInputSet().size(), 1U);
 
         // but sometimes it's possible, and we use an exact subset (0.4 + 0.6 = 1.0)
         coins.clear();
-        add_coin(coins, *wallet, MIN_CHANGE * 4 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 6 / 10);
-        add_coin(coins, *wallet, MIN_CHANGE * 8 / 10);
-        add_coin(coins, *wallet, 1111 * MIN_CHANGE);
-        const auto result21 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), MIN_CHANGE);
+        add_coin(coins, *wallet, CENT * 4 / 10);
+        add_coin(coins, *wallet, CENT * 6 / 10);
+        add_coin(coins, *wallet, CENT * 8 / 10);
+        add_coin(coins, *wallet, 1111 * CENT);
+        const auto result21 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT, CENT);
         BOOST_CHECK(result21);
-        BOOST_CHECK_EQUAL(result21->GetSelectedValue(), MIN_CHANGE);   // we should get the exact amount
+        BOOST_CHECK_EQUAL(result21->GetSelectedValue(), CENT);   // we should get the exact amount
         BOOST_CHECK_EQUAL(result21->GetInputSet().size(), 2U); // in two coins 0.4+0.6
 
         // test avoiding small change
         coins.clear();
-        add_coin(coins, *wallet, MIN_CHANGE * 5 / 100);
-        add_coin(coins, *wallet, MIN_CHANGE * 1);
-        add_coin(coins, *wallet, MIN_CHANGE * 100);
+        add_coin(coins, *wallet, CENT * 5 / 100);
+        add_coin(coins, *wallet, CENT * 1);
+        add_coin(coins, *wallet, CENT * 100);
 
         // trying to make 100.01 from these three coins
-        const auto result22 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), MIN_CHANGE * 10001 / 100);
+        const auto result22 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT * 10001 / 100, CENT);
         BOOST_CHECK(result22);
-        BOOST_CHECK_EQUAL(result22->GetSelectedValue(), MIN_CHANGE * 10105 / 100); // we should get all coins
+        BOOST_CHECK_EQUAL(result22->GetSelectedValue(), CENT * 10105 / 100); // we should get all coins
         BOOST_CHECK_EQUAL(result22->GetInputSet().size(), 3U);
 
         // but if we try to make 99.9, we should take the bigger of the two small coins to avoid small change
-        const auto result23 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), MIN_CHANGE * 9990 / 100);
+        const auto result23 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), CENT * 9990 / 100, CENT);
         BOOST_CHECK(result23);
-        BOOST_CHECK_EQUAL(result23->GetSelectedValue(), 101 * MIN_CHANGE);
+        BOOST_CHECK_EQUAL(result23->GetSelectedValue(), 101 * CENT);
         BOOST_CHECK_EQUAL(result23->GetInputSet().size(), 2U);
     }
 
@@ -581,12 +583,12 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
 
         // We only create the wallet once to save time, but we still run the coin selection RUN_TESTS times.
         for (int i = 0; i < RUN_TESTS; i++) {
-            const auto result24 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 2000);
+            const auto result24 = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_confirmed), 2000, CENT);
             BOOST_CHECK(result24);
 
-            if (amt - 2000 < MIN_CHANGE) {
+            if (amt - 2000 < CENT) {
                 // needs more than one input:
-                uint16_t returnSize = std::ceil((2000.0 + MIN_CHANGE)/amt);
+                uint16_t returnSize = std::ceil((2000.0 + CENT)/amt);
                 CAmount returnValue = amt * returnSize;
                 BOOST_CHECK_EQUAL(result24->GetSelectedValue(), returnValue);
                 BOOST_CHECK_EQUAL(result24->GetInputSet().size(), returnSize);
@@ -608,9 +610,9 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
         for (int i = 0; i < RUN_TESTS; i++) {
             // picking 50 from 100 coins doesn't depend on the shuffle,
             // but does depend on randomness in the stochastic approximation code
-            const auto result25 = KnapsackSolver(GroupCoins(coins), 50 * COIN);
+            const auto result25 = KnapsackSolver(GroupCoins(coins), 50 * COIN, CENT);
             BOOST_CHECK(result25);
-            const auto result26 = KnapsackSolver(GroupCoins(coins), 50 * COIN);
+            const auto result26 = KnapsackSolver(GroupCoins(coins), 50 * COIN, CENT);
             BOOST_CHECK(result26);
             BOOST_CHECK(!EqualResult(*result25, *result26));
 
@@ -621,9 +623,9 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
                 // When choosing 1 from 100 identical coins, 1% of the time, this test will choose the same coin twice
                 // which will cause it to fail.
                 // To avoid that issue, run the test RANDOM_REPEATS times and only complain if all of them fail
-                const auto result27 = KnapsackSolver(GroupCoins(coins), COIN);
+                const auto result27 = KnapsackSolver(GroupCoins(coins), COIN, CENT);
                 BOOST_CHECK(result27);
-                const auto result28 = KnapsackSolver(GroupCoins(coins), COIN);
+                const auto result28 = KnapsackSolver(GroupCoins(coins), COIN, CENT);
                 BOOST_CHECK(result28);
                 if (EqualResult(*result27, *result28))
                     fails++;
@@ -644,9 +646,9 @@ BOOST_AUTO_TEST_CASE(knapsack_solver_test)
             int fails = 0;
             for (int j = 0; j < RANDOM_REPEATS; j++)
             {
-                const auto result29 = KnapsackSolver(GroupCoins(coins), 90 * CENT);
+                const auto result29 = KnapsackSolver(GroupCoins(coins), 90 * CENT, CENT);
                 BOOST_CHECK(result29);
-                const auto result30 = KnapsackSolver(GroupCoins(coins), 90 * CENT);
+                const auto result30 = KnapsackSolver(GroupCoins(coins), 90 * CENT, CENT);
                 BOOST_CHECK(result30);
                 if (EqualResult(*result29, *result30))
                     fails++;
@@ -672,7 +674,7 @@ BOOST_AUTO_TEST_CASE(ApproximateBestSubset)
         add_coin(coins, *wallet, 1000 * COIN);
     add_coin(coins, *wallet, 3 * COIN);
 
-    const auto result = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1003 * COIN, rand);
+    const auto result = KnapsackSolver(KnapsackGroupOutputs(coins, *wallet, filter_standard), 1003 * COIN, CENT, rand);
     BOOST_CHECK(result);
     BOOST_CHECK_EQUAL(result->GetSelectedValue(), 1003 * COIN);
     BOOST_CHECK_EQUAL(result->GetInputSet().size(), 2U);
@@ -717,6 +719,7 @@ BOOST_AUTO_TEST_CASE(SelectCoins_test)
             rand,
             /* change_output_size= */ 34,
             /* change_spend_size= */ 148,
+            /*min_change_target=*/ CENT,
             /* effective_feerate= */ CFeeRate(0),
             /* long_term_feerate= */ CFeeRate(0),
             /* discard_feerate= */ CFeeRate(0),