From d812334d586c322e878aa47b78da53599d8dd177 Mon Sep 17 00:00:00 2001
From: alpo <62043214+AlpinYukseloglu@users.noreply.github.com>
Date: Thu, 20 Oct 2022 22:18:18 -0700
Subject: [PATCH] remove all uses of two-asset binary search solver (#3084)

---
 x/gamm/pool-models/stableswap/amm.go          | 38 -------------------
 .../pool-models/stableswap/amm_bench_test.go  |  6 ---
 x/gamm/pool-models/stableswap/amm_test.go     | 22 -----------
 3 files changed, 66 deletions(-)

diff --git a/x/gamm/pool-models/stableswap/amm.go b/x/gamm/pool-models/stableswap/amm.go
index 537d189931f..54043078293 100644
--- a/x/gamm/pool-models/stableswap/amm.go
+++ b/x/gamm/pool-models/stableswap/amm.go
@@ -64,9 +64,6 @@ func cfmmConstantMulti(xReserve, yReserve, u, v osmomath.BigDec) osmomath.BigDec
 // and the following expression for `a` in multi-asset pools:
 // xyz(x^2 + y^2 + w) = (x - a)(y + b)z((x - a)^2 + (y + b)^2 + w)
 func solveCfmm(xReserve, yReserve osmomath.BigDec, remReserves []osmomath.BigDec, yIn osmomath.BigDec) osmomath.BigDec {
-	if len(remReserves) == 0 {
-		return solveCFMMBinarySearch(cfmmConstant)(xReserve, yReserve, yIn)
-	}
 	wSumSquares := osmomath.ZeroDec()
 	for _, assetReserve := range remReserves {
 		wSumSquares = wSumSquares.Add(assetReserve.Mul(assetReserve))
@@ -161,41 +158,6 @@ var (
 	k_threshold = osmomath.NewDecWithPrec(1, 1) // Correct within a factor of 1 * 10^{-1}
 )
 
-// solveCFMMBinarySearch searches the correct dx using binary search over constant K.
-// added for future extension
-func solveCFMMBinarySearch(constantFunction func(osmomath.BigDec, osmomath.BigDec) osmomath.BigDec) func(osmomath.BigDec, osmomath.BigDec, osmomath.BigDec) osmomath.BigDec {
-	return func(xReserve, yReserve, yIn osmomath.BigDec) osmomath.BigDec {
-		if !xReserve.IsPositive() || !yReserve.IsPositive() {
-			panic("invalid input: reserves and input must be positive")
-		} else if yIn.Abs().GTE(yReserve) {
-			panic("cannot input more than pool reserves")
-		}
-		k := constantFunction(xReserve, yReserve)
-		yFinal := yReserve.Add(yIn)
-		xLowEst := osmomath.ZeroDec()
-		// we set upper bound at 2 * xReserve to accommodate negative yIns
-		xHighEst := xReserve.Mul(osmomath.NewBigDec(2))
-		maxIterations := 256
-		errTolerance := osmoutils.ErrTolerance{AdditiveTolerance: sdk.OneInt(), MultiplicativeTolerance: sdk.Dec{}}
-
-		// create single-input CFMM to pass into binary search
-		calc_x_est := func(xEst osmomath.BigDec) (osmomath.BigDec, error) {
-			return constantFunction(xEst, yFinal), nil
-		}
-
-		x_est, err := osmoutils.BinarySearchBigDec(calc_x_est, xLowEst, xHighEst, k, errTolerance, maxIterations)
-		if err != nil {
-			panic(err)
-		}
-
-		xOut := xReserve.Sub(x_est)
-		if xOut.GTE(xReserve) {
-			panic("invalid output: greater than full pool reserves")
-		}
-		return xOut
-	}
-}
-
 // solveCFMMBinarySearch searches the correct dx using binary search over constant K.
 // added for future extension
 func solveCFMMBinarySearchMulti(xReserve, yReserve, wSumSquares, yIn osmomath.BigDec) osmomath.BigDec {
diff --git a/x/gamm/pool-models/stableswap/amm_bench_test.go b/x/gamm/pool-models/stableswap/amm_bench_test.go
index e07cf136911..4a779a79238 100644
--- a/x/gamm/pool-models/stableswap/amm_bench_test.go
+++ b/x/gamm/pool-models/stableswap/amm_bench_test.go
@@ -14,12 +14,6 @@ func BenchmarkCFMM(b *testing.B) {
 	}
 }
 
-func BenchmarkBinarySearchTwoAsset(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		runCalcTwoAsset(solveCFMMBinarySearch(cfmmConstant))
-	}
-}
-
 func BenchmarkBinarySearchMultiAsset(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		runCalcMultiAsset(solveCFMMBinarySearchMulti)
diff --git a/x/gamm/pool-models/stableswap/amm_test.go b/x/gamm/pool-models/stableswap/amm_test.go
index c02baeb7816..da8c9a34eaa 100644
--- a/x/gamm/pool-models/stableswap/amm_test.go
+++ b/x/gamm/pool-models/stableswap/amm_test.go
@@ -406,28 +406,6 @@ func TestCFMMInvariantTwoAssets(t *testing.T) {
 	}
 }
 
-func TestCFMMInvariantTwoAssetsBinarySearch(t *testing.T) {
-	kErrTolerance := osmomath.OneDec()
-
-	tests := twoAssetCFMMTestCases
-
-	for name, test := range tests {
-		t.Run(name, func(t *testing.T) {
-			// system under test
-			sut := func() {
-				// using two-asset binary search cfmm solver
-				k0 := cfmmConstant(test.xReserve, test.yReserve)
-				xOut := solveCFMMBinarySearch(cfmmConstant)(test.xReserve, test.yReserve, test.yIn)
-
-				k1 := cfmmConstant(test.xReserve.Sub(xOut), test.yReserve.Add(test.yIn))
-				osmomath.DecApproxEq(t, k0, k1, kErrTolerance)
-			}
-
-			osmoassert.ConditionalPanic(t, test.expectPanic, sut)
-		})
-	}
-}
-
 func TestCFMMInvariantTwoAssetsDirect(t *testing.T) {
 	kErrTolerance := osmomath.OneDec()