perf: use direct comparison

[proost]

previous PR: apache/datasketches-characterization#89

current go version theta sketch performance is bad. one of reasons using errors.Is.

generally, go recommends "errors.Is" for error check, but we are using sentinel error. So we can avoid using errors.Is.

benchmark code:

func BenchmarkUpdateSketchErrorHandling(b *testing.B) {
	b.Run("UpdateInt64_NewKeys", func(b *testing.B) {
		sketch, _ := NewQuickSelectUpdateSketch()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			_ = sketch.UpdateInt64(int64(i))
		}
	})

	b.Run("UpdateInt64_DuplicateKeys", func(b *testing.B) {
		sketch, _ := NewQuickSelectUpdateSketch()
		_ = sketch.UpdateInt64(42)
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			_ = sketch.UpdateInt64(42)
		}
	})
}

• Current UpdateSketch

goos: darwin
goarch: arm64
pkg: github.com/apache/datasketches-go/theta
cpu: Apple M1 Pro
BenchmarkUpdateSketchErrorHandling
BenchmarkUpdateSketchErrorHandling/UpdateInt64_NewKeys
BenchmarkUpdateSketchErrorHandling/UpdateInt64_NewKeys-10         	 7506458	       150.9 ns/op
BenchmarkUpdateSketchErrorHandling/UpdateInt64_DuplicateKeys
BenchmarkUpdateSketchErrorHandling/UpdateInt64_DuplicateKeys-10   	165562837	         7.287 ns/op

• New UpdateSketch

BenchmarkUpdateSketchErrorHandling
BenchmarkUpdateSketchErrorHandling/UpdateInt64_NewKeys
BenchmarkUpdateSketchErrorHandling/UpdateInt64_NewKeys-10         	 7503918	       143.6 ns/op
BenchmarkUpdateSketchErrorHandling/UpdateInt64_DuplicateKeys
BenchmarkUpdateSketchErrorHandling/UpdateInt64_DuplicateKeys-10   	166055470	         7.227 ns/op

benchmark code:

func BenchmarkUnionUpdate(b *testing.B) {
	b.Run("Update_NewKeys", func(b *testing.B) {
		sketches := make([]*QuickSelectUpdateSketch, b.N)
		for i := 0; i < b.N; i++ {
			sketch, _ := NewQuickSelectUpdateSketch()
			sketch.UpdateInt64(int64(i))
			sketches[i] = sketch
		}

		union, _ := NewUnion()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			_ = union.Update(sketches[i])
		}
	})

	b.Run("Update_DuplicateKeys", func(b *testing.B) {
		sketches := make([]*QuickSelectUpdateSketch, b.N)
		for i := 0; i < b.N; i++ {
			sketch, _ := NewQuickSelectUpdateSketch()
			sketch.UpdateInt64(42)
			sketches[i] = sketch
		}

		union, _ := NewUnion()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			_ = union.Update(sketches[i])
		}
	})
}

• Current Union Update

goos: darwin
goarch: arm64
pkg: github.com/apache/datasketches-go/theta
cpu: Apple M1 Pro
BenchmarkUnionUpdate
BenchmarkUnionUpdate/Update_NewKeys
BenchmarkUnionUpdate/Update_NewKeys-10         	 8556276	       457.7 ns/op
BenchmarkUnionUpdate/Update_DuplicateKeys
BenchmarkUnionUpdate/Update_DuplicateKeys-10   	 7176099	       443.6 ns/op

• New Union Update

goos: darwin
goarch: arm64
pkg: github.com/apache/datasketches-go/theta
cpu: Apple M1 Pro
BenchmarkUnionUpdate
BenchmarkUnionUpdate/Update_NewKeys
BenchmarkUnionUpdate/Update_NewKeys-10         	 8699008	       430.7 ns/op
BenchmarkUnionUpdate/Update_DuplicateKeys
BenchmarkUnionUpdate/Update_DuplicateKeys-10   	 7546215	       292.6 ns/op

[proost]

Suggestion:

If breaking change is acceptable, Because we currently not release theta sketch officially, I'd like to change returning format error(like this) to sentinel error. Chaning to sentinel error avoids heap allocation when hash exceeds theta.

[freakyzoidberg]

Thats cool, one of the benefit of not having done an official release yet