From f002e54d2679e02ed31278a3e925e4f20f3aaa1d Mon Sep 17 00:00:00 2001
From: Emmanuel T Odeke <emmanuel@orijtech.com>
Date: Tue, 2 Aug 2022 07:00:08 -0700
Subject: [PATCH] perf: math: precompute & use square of precisionReuse instead
 of 2 repeated computations (#12794)

---
 math/dec.go      | 13 ++++++-------
 math/dec_test.go | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/math/dec.go b/math/dec.go
index 667bfec50b..90bb8c7ace 100644
--- a/math/dec.go
+++ b/math/dec.go
@@ -342,11 +342,12 @@ func (d LegacyDec) Quo(d2 LegacyDec) LegacyDec {
 	return d.ImmutOp(LegacyDec.QuoMut, d2)
 }
 
+var squaredPrecisionReuse = new(big.Int).Mul(precisionReuse, precisionReuse)
+
 // mutable quotient
 func (d LegacyDec) QuoMut(d2 LegacyDec) LegacyDec {
-	// multiply precision twice
-	d.i.Mul(d.i, precisionReuse)
-	d.i.Mul(d.i, precisionReuse)
+	// multiply by precision twice
+	d.i.Mul(d.i, squaredPrecisionReuse)
 	d.i.Quo(d.i, d2.i)
 
 	chopPrecisionAndRound(d.i)
@@ -364,8 +365,7 @@ func (d LegacyDec) QuoTruncate(d2 LegacyDec) LegacyDec {
 // mutable quotient truncate
 func (d LegacyDec) QuoTruncateMut(d2 LegacyDec) LegacyDec {
 	// multiply precision twice
-	d.i.Mul(d.i, precisionReuse)
-	d.i.Mul(d.i, precisionReuse)
+	d.i.Mul(d.i, squaredPrecisionReuse)
 	d.i.Quo(d.i, d2.i)
 
 	chopPrecisionAndTruncate(d.i)
@@ -383,8 +383,7 @@ func (d LegacyDec) QuoRoundUp(d2 LegacyDec) LegacyDec {
 // mutable quotient, round up
 func (d LegacyDec) QuoRoundupMut(d2 LegacyDec) LegacyDec {
 	// multiply precision twice
-	d.i.Mul(d.i, precisionReuse)
-	d.i.Mul(d.i, precisionReuse)
+	d.i.Mul(d.i, squaredPrecisionReuse)
 	d.i.Quo(d.i, d2.i)
 
 	chopPrecisionAndRoundUp(d.i)
diff --git a/math/dec_test.go b/math/dec_test.go
index d390d45201..637ef71ee0 100644
--- a/math/dec_test.go
+++ b/math/dec_test.go
@@ -619,3 +619,50 @@ func BenchmarkMarshalTo(b *testing.B) {
 		}
 	}
 }
+
+var sink interface{}
+
+func BenchmarkLegacyQuoMut(b *testing.B) {
+	b1 := math.LegacyNewDec(17e2 + 8371)
+	b2 := math.LegacyNewDec(4371)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+            sink = b1.QuoMut(b2)
+	}
+
+	if sink == nil {
+		b.Fatal("Benchmark did not run")
+	}
+	sink = (interface{})(nil)
+}
+
+func BenchmarkLegacyQuoTruncateMut(b *testing.B) {
+	b1 := math.LegacyNewDec(17e2 + 8371)
+	b2 := math.LegacyNewDec(4371)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+            sink = b1.QuoTruncateMut(b2)
+	}
+
+	if sink == nil {
+		b.Fatal("Benchmark did not run")
+	}
+	sink = (interface{})(nil)
+}
+
+func BenchmarkLegacyQuoRoundupMut(b *testing.B) {
+	b1 := math.LegacyNewDec(17e2 + 8371)
+	b2 := math.LegacyNewDec(4371)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+            sink = b1.QuoRoundupMut(b2)
+	}
+
+	if sink == nil {
+		b.Fatal("Benchmark did not run")
+	}
+	sink = (interface{})(nil)
+}