Fix/zero weights panic

CHANGELOG.md

@@ -6,12 +6,16 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
-## [Unreleased]
+## [1.0.1] 12-03-2017
 ### Added
+- Bug fix to return error when no weights have been set
 
+## [1.0.0] 12-03-2017
+### Added
+- Initial Release
 
 
-[Unreleased]: https://github.com/while-loop/go-walk/compare/v0.0.1...HEAD
-[0.0.2]: https://github.com/while-loop/go-walk/compare/v0.0.1...v0.0.2
+[1.0.0]: https://github.com/while-loop/go-walk/compare/0.0.1...HEAD
+[1.0.1]: https://github.com/while-loop/go-walk/compare/1.0.0...1.0.1
 
 [comment]: # (Added, Changed, Removed)

walk/randomwalk.go

@@ -68,8 +68,11 @@ func (w *RandomWalk) Walk(iterations uint32) error {
 	}
 
 	ws, sum := w.preprocess()
-	for i := uint32(0); i < iterations; i++ {
+	if sum <= 0 {
+		return errors.New("Sum of weights is <= 0")
+	}
 
+	for i := uint32(0); i < iterations; i++ {
 		switch getRandy(ws, sum) {
 		case lEFT:
 			w.Walker.Left()
@@ -91,6 +94,10 @@ func (w *RandomWalk) Walk(iterations uint32) error {
 // Get a random direction given a set of normalized weights
 // Using the Sum of Weights method
 func getRandy(ws weights, sum uint64) int {
+	if sum <= 0 {
+		return -1
+	}
+
 	randy := r.Int63n(int64(sum))
 	ttl := int64(0)
 

walk/randomwalk_test.go

@@ -32,7 +32,6 @@ func TestInterfaceCallsMethods(t *testing.T) {
 	assert.Equal(t, 0, mw.r, "right sums not 0")
 	assert.Equal(t, maxIts, mw.u, "up sums not maxIts")
 	assert.Equal(t, 0, mw.d, "down sums not 0")
-
 }
 
 func TestInterfaceCallsMethodsEqually(t *testing.T) {
@@ -94,7 +93,7 @@ func TestPreprocessAssignsCorrectDirEnum(t *testing.T) {
 	assert.Equal(t, uint64(l)+uint64(r)+uint64(u)+uint64(d), sum, "", l, r, u, d)
 }
 
-func TestZeroWeightsDontExecute(t *testing.T) {
+func TestPrependedZeroWeightsDontExecute(t *testing.T) {
 	maxIts := 100000
 	sums := map[int]int{
 		lEFT:  0,
@@ -110,10 +109,10 @@ func TestZeroWeightsDontExecute(t *testing.T) {
 
 	assert.Equal(t, 4, len(sums), "Unknown direction given", sums)
 
-	assert.Equal(t, 0, sums[lEFT], "left sums not 0")
-	assert.Equal(t, 0, sums[rIGHT], "right sums not 0")
-	assert.Equal(t, 0, sums[uP], "up sums not 0")
-	assert.Equal(t, maxIts, sums[dOWN], "not all dirs were down")
+	assert.Equal(t, 0, sums[lEFT], "left sums not 0", sums[lEFT])
+	assert.Equal(t, 0, sums[rIGHT], "right sums not 0", sums[rIGHT])
+	assert.Equal(t, 0, sums[uP], "up sums not 0", sums[uP])
+	assert.Equal(t, maxIts, sums[dOWN], "not all dirs were down", sums[dOWN])
 }
 
 func TestHalfWeightsDontExecute(t *testing.T) {
@@ -138,6 +137,44 @@ func TestHalfWeightsDontExecute(t *testing.T) {
 	assert.True(t, sums[dOWN] >= maxIts/3.0, "down sums not distributed", sums[dOWN], maxIts/3.0)
 }
 
+func TestZeroWeightsReturnsNegative1(t *testing.T) {
+	maxIts := 100000
+	sums := map[int]int{
+		lEFT:  0,
+		rIGHT: 0,
+		uP:    0,
+		dOWN:  0,
+	}
+
+	weights, sum := NewRandomWalk(0, 0, 0, 0, nil).preprocess()
+	for i := 0; i < maxIts; i++ {
+		sums[getRandy(weights, sum)]++
+	}
+
+	assert.Equal(t, 5, len(sums), "Unknown direction given", sums)
+
+	assert.Equal(t, maxIts, sums[-1], "-1 sums not max Its", sums[-1])
+	assert.Equal(t, 0, sums[lEFT], "left sums not 0", sums[lEFT])
+	assert.Equal(t, 0, sums[rIGHT], "right sums not 0", sums[rIGHT])
+	assert.Equal(t, 0, sums[uP], "up sums not 0", sums[uP])
+	assert.Equal(t, 0, sums[dOWN], "down sums not 0", sums[dOWN])
+}
+
+func TestZeroWeightsReturnErrorWalking(t *testing.T) {
+	maxIts := uint32(100000)
+
+	mw := &TestWalker{}
+	rw := NewRandomWalk(0, 0, 0, 0, mw)
+	err := rw.Walk(maxIts)
+	assert.Error(t, err)
+	assert.Equal(t, "Sum of weights is <= 0", err.Error())
+
+	assert.Equal(t, 0, mw.l, "left sums not 0")
+	assert.Equal(t, 0, mw.r, "right sums not 0")
+	assert.Equal(t, 0, mw.u, "up sums not 0")
+	assert.Equal(t, 0, mw.d, "down sums not 0")
+}
+
 type TestWalker struct {
 	l, r, u, d int
 }