lib/{decimal,encoding}: optimize float64<->decimal conversion for arrays with zeros or ones

Time series with only zeros or ones frequently occur in monitoring, so it is worth optimizing their handling.

lib/decimal/decimal.go

@@ -3,6 +3,8 @@ package decimal
 import (
 	"math"
 	"sync"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fastnum"
 )
 
 // CalibrateScale calibrates a and b with the corresponding exponents ae, be
@@ -81,6 +83,13 @@ func ExtendInt64sCapacity(dst []int64, additionalItems int) []int64 {
 // AppendDecimalToFloat converts each item in va to f=v*10^e, appends it
 // to dst and returns the resulting dst.
 func AppendDecimalToFloat(dst []float64, va []int64, e int16) []float64 {
+	if fastnum.IsInt64Zeros(va) {
+		return fastnum.AppendFloat64Zeros(dst, len(va))
+	}
+	if e == 0 && fastnum.IsInt64Ones(va) {
+		return fastnum.AppendFloat64Ones(dst, len(va))
+	}
+
 	// Extend dst capacity in order to eliminate memory allocations below.
 	dst = ExtendFloat64sCapacity(dst, len(va))
 
@@ -108,6 +117,14 @@ func AppendFloatToDecimal(dst []int64, src []float64) (va []int64, e int16) {
 	if len(src) == 0 {
 		return dst, 0
 	}
+	if fastnum.IsFloat64Zeros(src) {
+		dst = fastnum.AppendInt64Zeros(dst, len(src))
+		return dst, 0
+	}
+	if fastnum.IsFloat64Ones(src) {
+		dst = fastnum.AppendInt64Ones(dst, len(src))
+		return dst, 0
+	}
 
 	// Extend dst capacity in order to eliminate memory allocations below.
 	dst = ExtendInt64sCapacity(dst, len(src))

lib/encoding/encoding.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/decimal"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fastnum"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 )
 
@@ -201,6 +202,14 @@ func unmarshalInt64Array(dst []int64, src []byte, mt MarshalType, firstValue int
 		if len(src) > 0 {
 			return nil, fmt.Errorf("unexpected data left in const encoding: %d bytes", len(src))
 		}
+		if firstValue == 0 {
+			dst = fastnum.AppendInt64Zeros(dst, itemsCount)
+			return dst, nil
+		}
+		if firstValue == 1 {
+			dst = fastnum.AppendInt64Ones(dst, itemsCount)
+			return dst, nil
+		}
 		for itemsCount > 0 {
 			dst = append(dst, firstValue)
 			itemsCount--
@@ -267,6 +276,14 @@ func isConst(a []int64) bool {
 	if len(a) == 0 {
 		return false
 	}
+	if fastnum.IsInt64Zeros(a) {
+		// Fast path for array containing only zeros.
+		return true
+	}
+	if fastnum.IsInt64Ones(a) {
+		// Fast path for array containing only ones.
+		return true
+	}
 	v1 := a[0]
 	for _, v := range a {
 		if v != v1 {

lib/fastnum/fastnum.go

@@ -0,0 +1,144 @@
+package fastnum
+
+import (
+	"bytes"
+	"unsafe"
+)
+
+// AppendInt64Zeros appends items zeros to dst and returns the result.
+//
+// It is faster than the corresponding loop.
+func AppendInt64Zeros(dst []int64, items int) []int64 {
+	return appendInt64Data(dst, items, int64Zeros[:])
+}
+
+// AppendInt64Ones appends items ones to dst and returns the result.
+//
+// It is faster than the correponding loop.
+func AppendInt64Ones(dst []int64, items int) []int64 {
+	return appendInt64Data(dst, items, int64Ones[:])
+}
+
+// AppendFloat64Zeros appends items zeros to dst and returns the result.
+//
+// It is faster than the corresponding loop.
+func AppendFloat64Zeros(dst []float64, items int) []float64 {
+	return appendFloat64Data(dst, items, float64Zeros[:])
+}
+
+// AppendFloat64Ones appends items ones to dst and returns the result.
+//
+// It is faster than the corresponding loop.
+func AppendFloat64Ones(dst []float64, items int) []float64 {
+	return appendFloat64Data(dst, items, float64Ones[:])
+}
+
+// IsInt64Zeros checks whether a contains only zeros.
+func IsInt64Zeros(a []int64) bool {
+	return isInt64Data(a, int64Zeros[:])
+}
+
+// IsInt64Ones checks whether a contains only ones.
+func IsInt64Ones(a []int64) bool {
+	return isInt64Data(a, int64Ones[:])
+}
+
+// IsFloat64Zeros checks whether a contains only zeros.
+func IsFloat64Zeros(a []float64) bool {
+	return isFloat64Data(a, float64Zeros[:])
+}
+
+// IsFloat64Ones checks whether a contains only ones.
+func IsFloat64Ones(a []float64) bool {
+	return isFloat64Data(a, float64Ones[:])
+}
+
+func appendInt64Data(dst []int64, items int, src []int64) []int64 {
+	for items > 0 {
+		n := len(src)
+		if n > items {
+			n = items
+		}
+		dst = append(dst, src[:n]...)
+		items -= n
+	}
+	return dst
+}
+
+func appendFloat64Data(dst []float64, items int, src []float64) []float64 {
+	for items > 0 {
+		n := len(src)
+		if n > items {
+			n = items
+		}
+		dst = append(dst, src[:n]...)
+		items -= n
+	}
+	return dst
+}
+
+func isInt64Data(a, data []int64) bool {
+	if len(a) == 0 {
+		return true
+	}
+	if len(data) != 8*1024 {
+		panic("len(data) must equal to 8*1024")
+	}
+	b := (*[64 * 1024]byte)(unsafe.Pointer(&data[0]))
+	for len(a) > 0 {
+		n := len(data)
+		if n > len(a) {
+			n = len(a)
+		}
+		x := a[:n]
+		a = a[n:]
+		xb := (*[64 * 1024]byte)(unsafe.Pointer(&x[0]))
+		xbLen := len(x) * 8
+		if !bytes.Equal(xb[:xbLen], b[:xbLen]) {
+			return false
+		}
+	}
+	return true
+}
+
+func isFloat64Data(a, data []float64) bool {
+	if len(a) == 0 {
+		return true
+	}
+	if len(data) != 8*1024 {
+		panic("len(data) must equal to 8*1024")
+	}
+	b := (*[64 * 1024]byte)(unsafe.Pointer(&data[0]))
+	for len(a) > 0 {
+		n := len(data)
+		if n > len(a) {
+			n = len(a)
+		}
+		x := a[:n]
+		a = a[n:]
+		xb := (*[64 * 1024]byte)(unsafe.Pointer(&x[0]))
+		xbLen := len(x) * 8
+		if !bytes.Equal(xb[:xbLen], b[:xbLen]) {
+			return false
+		}
+	}
+	return true
+}
+
+var (
+	int64Zeros [8 * 1024]int64
+	int64Ones  = func() (a [8 * 1024]int64) {
+		for i := 0; i < len(a); i++ {
+			a[i] = 1
+		}
+		return a
+	}()
+
+	float64Zeros [8 * 1024]float64
+	float64Ones  = func() (a [8 * 1024]float64) {
+		for i := 0; i < len(a); i++ {
+			a[i] = 1
+		}
+		return a
+	}()
+)

lib/fastnum/fastnum_test.go

@@ -0,0 +1,192 @@
+package fastnum
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestIsInt64Zeros(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := make([]int64, n)
+			if !IsInt64Zeros(a) {
+				t.Fatalf("IsInt64Zeros must return true")
+			}
+			if len(a) > 0 {
+				a[len(a)-1] = 1
+				if IsInt64Zeros(a) {
+					t.Fatalf("IsInt64Zeros must return false")
+				}
+			}
+		})
+	}
+}
+
+func TestIsInt64Ones(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := make([]int64, n)
+			for i := 0; i < n; i++ {
+				a[i] = 1
+			}
+			if !IsInt64Ones(a) {
+				t.Fatalf("IsInt64Ones must return true")
+			}
+			if len(a) > 0 {
+				a[len(a)-1] = 0
+				if IsInt64Ones(a) {
+					t.Fatalf("IsInt64Ones must return false")
+				}
+			}
+		})
+	}
+}
+
+func TestIsFloat64Zeros(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := make([]float64, n)
+			if !IsFloat64Zeros(a) {
+				t.Fatalf("IsInt64Zeros must return true")
+			}
+			if len(a) > 0 {
+				a[len(a)-1] = 1
+				if IsFloat64Zeros(a) {
+					t.Fatalf("IsInt64Zeros must return false")
+				}
+			}
+		})
+	}
+}
+
+func TestIsFloat64Ones(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := make([]float64, n)
+			for i := 0; i < n; i++ {
+				a[i] = 1
+			}
+			if !IsFloat64Ones(a) {
+				t.Fatalf("IsInt64Ones must return true")
+			}
+			if len(a) > 0 {
+				a[len(a)-1] = 0
+				if IsFloat64Ones(a) {
+					t.Fatalf("IsInt64Ones must return false")
+				}
+			}
+		})
+	}
+}
+
+func TestAppendInt64Zeros(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := AppendInt64Zeros(nil, n)
+			if len(a) != n {
+				t.Fatalf("unexpected len(a); got %d; want %d", len(a), n)
+			}
+			if !IsInt64Zeros(a) {
+				t.Fatalf("IsInt64Zeros must return true")
+			}
+
+			prefix := []int64{1, 2, 3}
+			a = AppendInt64Zeros(prefix, n)
+			if len(a) != len(prefix)+n {
+				t.Fatalf("unexpected len(a) with prefix; got %d; want %d", len(a), len(prefix)+n)
+			}
+			for i := 0; i < len(prefix); i++ {
+				if a[i] != prefix[i] {
+					t.Fatalf("unexpected prefix[%d]; got %d; want %d", i, a[i], prefix[i])
+				}
+			}
+			if !IsInt64Zeros(a[len(prefix):]) {
+				t.Fatalf("IsInt64Zeros for prefixed a must return true")
+			}
+		})
+	}
+}
+
+func TestAppendInt64Ones(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := AppendInt64Ones(nil, n)
+			if len(a) != n {
+				t.Fatalf("unexpected len(a); got %d; want %d", len(a), n)
+			}
+			if !IsInt64Ones(a) {
+				t.Fatalf("IsInt64Ones must return true")
+			}
+
+			prefix := []int64{1, 2, 3}
+			a = AppendInt64Ones(prefix, n)
+			if len(a) != len(prefix)+n {
+				t.Fatalf("unexpected len(a) with prefix; got %d; want %d", len(a), len(prefix)+n)
+			}
+			for i := 0; i < len(prefix); i++ {
+				if a[i] != prefix[i] {
+					t.Fatalf("unexpected prefix[%d]; got %d; want %d", i, a[i], prefix[i])
+				}
+			}
+			if !IsInt64Ones(a[len(prefix):]) {
+				t.Fatalf("IsInt64Ones for prefixed a must return true")
+			}
+		})
+	}
+}
+
+func TestAppendFloat64Zeros(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := AppendFloat64Zeros(nil, n)
+			if len(a) != n {
+				t.Fatalf("unexpected len(a); got %d; want %d", len(a), n)
+			}
+			if !IsFloat64Zeros(a) {
+				t.Fatalf("IsFloat64Zeros must return true")
+			}
+
+			prefix := []float64{1, 2, 3}
+			a = AppendFloat64Zeros(prefix, n)
+			if len(a) != len(prefix)+n {
+				t.Fatalf("unexpected len(a) with prefix; got %d; want %d", len(a), len(prefix)+n)
+			}
+			for i := 0; i < len(prefix); i++ {
+				if a[i] != prefix[i] {
+					t.Fatalf("unexpected prefix[%d]; got %f; want %f", i, a[i], prefix[i])
+				}
+			}
+			if !IsFloat64Zeros(a[len(prefix):]) {
+				t.Fatalf("IsFloat64Zeros for prefixed a must return true")
+			}
+		})
+	}
+}
+
+func TestAppendFloat64Ones(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000, 1e4, 1e5, 8*1024 + 1} {
+		t.Run(fmt.Sprintf("%d_items", n), func(t *testing.T) {
+			a := AppendFloat64Ones(nil, n)
+			if len(a) != n {
+				t.Fatalf("unexpected len(a); got %d; want %d", len(a), n)
+			}
+			if !IsFloat64Ones(a) {
+				t.Fatalf("IsFloat64Ones must return true")
+			}
+
+			prefix := []float64{1, 2, 3}
+			a = AppendFloat64Ones(prefix, n)
+			if len(a) != len(prefix)+n {
+				t.Fatalf("unexpected len(a) with prefix; got %d; want %d", len(a), len(prefix)+n)
+			}
+			for i := 0; i < len(prefix); i++ {
+				if a[i] != prefix[i] {
+					t.Fatalf("unexpected prefix[%d]; got %f; want %f", i, a[i], prefix[i])
+				}
+			}
+			if !IsFloat64Ones(a[len(prefix):]) {
+				t.Fatalf("IsFloat64Ones for prefixed a must return true")
+			}
+		})
+	}
+}