diff options
| -rw-r--r-- | prog/heatmap.go | 26 | ||||
| -rw-r--r-- | prog/heatmap_test.go | 4 | ||||
| -rw-r--r-- | prog/mutation.go | 8 |
3 files changed, 20 insertions, 18 deletions
diff --git a/prog/heatmap.go b/prog/heatmap.go index 51daaf251..d1c5ea3b9 100644 --- a/prog/heatmap.go +++ b/prog/heatmap.go @@ -16,8 +16,8 @@ import ( // 2. Select random indices according to the probability distribution: // `idx := hm.ChooseLocation(r)`. type Heatmap interface { - ChooseLocation(r *rand.Rand) int - Size() int + NumMutations() int + ChooseLocation() int } // Generic heatmaps model a probability distribution based on sparse data, @@ -25,27 +25,31 @@ type Heatmap interface { // views data as a series of chunks of length `granularity`, ignoring chunks // which are a single repeated byte. Indices are chosen uniformly amongst the // remaining "interesting" segments. -func MakeGenericHeatmap(data []byte) Heatmap { +func MakeGenericHeatmap(data []byte, r *rand.Rand) Heatmap { if len(data) == 0 { panic("cannot create a GenericHeatmap with no data") } - var hm GenericHeatmap + hm := &GenericHeatmap{ + r: r, + } hm.length, hm.segments = calculateLengthAndSegments(data, granularity) - return &hm + return hm +} + +func (hm *GenericHeatmap) NumMutations() int { + // At least two mutations, up to about one mutation every 128 KB of heatmap size. + return hm.r.Intn(hm.length/(1<<17)+1) + 2 } -func (hm *GenericHeatmap) ChooseLocation(r *rand.Rand) int { +func (hm *GenericHeatmap) ChooseLocation() int { // Uniformly choose an index within one of the segments. - heatmapIdx := r.Intn(hm.length) + heatmapIdx := hm.r.Intn(hm.length) rawIdx := translateIdx(heatmapIdx, hm.segments) return rawIdx } -func (hm *GenericHeatmap) Size() int { - return hm.length -} - type GenericHeatmap struct { + r *rand.Rand segments []segment // "Interesting" parts of the data. length int // Sum of all segment lengths. } diff --git a/prog/heatmap_test.go b/prog/heatmap_test.go index 4103a4f97..9c891f258 100644 --- a/prog/heatmap_test.go +++ b/prog/heatmap_test.go @@ -57,10 +57,10 @@ func TestGenericHeatmap(t *testing.T) { t.Fatalf("bad decode: %v", err) } for i := 0; i < iters; i++ { - hm := MakeGenericHeatmap(data).(*GenericHeatmap) + hm := MakeGenericHeatmap(data, r).(*GenericHeatmap) for j := 0; j < tries; j++ { - index := hm.ChooseLocation(r) + index := hm.ChooseLocation() if !checkIndex(index, len(data), test.regions) { hm.debugPrint(t, data, test.regions) t.Fatalf("selected index %d does not fall in a region\n", index) diff --git a/prog/mutation.go b/prog/mutation.go index 881403247..96e11516c 100644 --- a/prog/mutation.go +++ b/prog/mutation.go @@ -401,11 +401,9 @@ func (r *randGen) mutateImage(image []byte) (data []byte, retry bool) { if len(data) == 0 { return image, true // Do not mutate empty data. } - hm := MakeGenericHeatmap(data) - // At least two mutations, up to about one mutation every 128 KB of heatmap size. - numMutations := r.Intn(hm.Size()/(1<<17)+1) + 2 - for i := 0; i < numMutations; i++ { - index := hm.ChooseLocation(r.Rand) + hm := MakeGenericHeatmap(data, r.Rand) + for i := hm.NumMutations(); i > 0; i-- { + index := hm.ChooseLocation() width := 1 << uint(r.Intn(4)) if index+width > len(data) { width = 1 |