sigmoid strat placeholder

bitswap/strategy.go

@@ -0,0 +1,20 @@
+package bitswap
+
+import (
+	"math"
+)
+
+func probabilitySend(ratio float64) float64 {
+	x := 1 + math.Exp(6-3*ratio)
+	y := 1 / x
+	return 1 - y
+}
+
+type debtRatio struct {
+	BytesSent uint64
+	BytesRecv uint64
+}
+
+func (dr *debtRatio) Value() float64 {
+	return float64(dr.BytesSent) / float64(dr.BytesRecv+1)
+}

bitswap/strategy_test.go

@@ -0,0 +1,17 @@
+package bitswap
+
+import (
+	"testing"
+)
+
+func TestProbabilitySendDecreasesAsRatioIncreases(t *testing.T) {
+	grateful := debtRatio{BytesSent: 0, BytesRecv: 10000}
+	pWhenGrateful := probabilitySend(grateful.Value())
+
+	abused := debtRatio{BytesSent: 10000, BytesRecv: 0}
+	pWhenAbused := probabilitySend(abused.Value())
+
+	if pWhenGrateful < pWhenAbused {
+		t.Fail()
+	}
+}