test(bench): benchmark suite for cluster, MMR, selector, and compress (#69)

Implements issue #24. Adds deterministic benchmarks using fixed-seed
random embeddings so results are reproducible across runs:

- BenchmarkCluster_{10,50,100,500}Chunks (pkg/contextlab)
- BenchmarkMMR_{10,50}Chunks (pkg/contextlab)
- BenchmarkSelector_{10,50}Clusters (pkg/contextlab)
- BenchmarkCompress_{Short,Long}Text (pkg/compress)

Run with: go test -bench=. -benchmem ./pkg/contextlab/... ./pkg/compress/...

Co-authored-by: Ona <no-reply@ona.com>

Author: Siddhant-K-code

pkg/compress/bench_test.go

@@ -0,0 +1,32 @@
+package compress
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/Siddhant-K-code/distill/pkg/types"
+)
+
+func BenchmarkCompress_ShortText(b *testing.B) {
+	c := NewExtractiveCompressor()
+	ctx := context.Background()
+	chunk := types.Chunk{ID: "bench", Text: "This is a short text for compression benchmarking."}
+	opts := DefaultOptions()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _, _ = c.Compress(ctx, []types.Chunk{chunk}, opts)
+	}
+}
+
+func BenchmarkCompress_LongText(b *testing.B) {
+	c := NewExtractiveCompressor()
+	ctx := context.Background()
+	long := strings.Repeat("This is a longer text with more content for compression benchmarking. ", 50)
+	chunk := types.Chunk{ID: "bench", Text: long}
+	opts := DefaultOptions()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _, _ = c.Compress(ctx, []types.Chunk{chunk}, opts)
+	}
+}

pkg/contextlab/bench_test.go

@@ -0,0 +1,100 @@
+package contextlab
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/Siddhant-K-code/distill/pkg/types"
+)
+
+// deterministicEmbedding generates a reproducible embedding for a given seed.
+// Using a fixed seed ensures benchmark results are stable across runs.
+func deterministicEmbedding(seed int64, dims int) []float32 {
+	rng := rand.New(rand.NewSource(seed))
+	v := make([]float32, dims)
+	for i := range v {
+		v[i] = rng.Float32()
+	}
+	return v
+}
+
+// makeBenchChunks builds n chunks with deterministic embeddings.
+func makeBenchChunks(n, dims int) []types.Chunk {
+	chunks := make([]types.Chunk, n)
+	for i := range chunks {
+		chunks[i] = types.Chunk{
+			ID:        string(rune('A'+i%26)) + string(rune('0'+i/26%10)),
+			Text:      "benchmark chunk content for semantic deduplication testing",
+			Embedding: deterministicEmbedding(int64(i), dims),
+		}
+	}
+	return chunks
+}
+
+func BenchmarkCluster_10Chunks(b *testing.B) {
+	chunks := makeBenchChunks(10, 128)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = ClusterByThreshold(chunks, 0.15)
+	}
+}
+
+func BenchmarkCluster_50Chunks(b *testing.B) {
+	chunks := makeBenchChunks(50, 128)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = ClusterByThreshold(chunks, 0.15)
+	}
+}
+
+func BenchmarkCluster_100Chunks(b *testing.B) {
+	chunks := makeBenchChunks(100, 128)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = ClusterByThreshold(chunks, 0.15)
+	}
+}
+
+func BenchmarkCluster_500Chunks(b *testing.B) {
+	chunks := makeBenchChunks(500, 128)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = ClusterByThreshold(chunks, 0.15)
+	}
+}
+
+func BenchmarkMMR_10Chunks(b *testing.B) {
+	chunks := makeBenchChunks(10, 128)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = MMRRerank(chunks, 0.7, 5)
+	}
+}
+
+func BenchmarkMMR_50Chunks(b *testing.B) {
+	chunks := makeBenchChunks(50, 128)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = MMRRerank(chunks, 0.7, 10)
+	}
+}
+
+func BenchmarkSelector_10Clusters(b *testing.B) {
+	chunks := makeBenchChunks(10, 128)
+	result := ClusterByThreshold(chunks, 0.15)
+	sel := NewSelector(DefaultSelectorConfig())
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = sel.Select(result)
+	}
+}
+
+func BenchmarkSelector_50Clusters(b *testing.B) {
+	chunks := makeBenchChunks(50, 128)
+	result := ClusterByThreshold(chunks, 0.15)
+	sel := NewSelector(DefaultSelectorConfig())
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = sel.Select(result)
+	}
+}