[#8] hrw: Do not allocate 2 slices for sort

Currently we allocate `rule` and then create `dist` which depends on it.
In this commit we create `dist` directly.

```
goos: linux
goarch: amd64
pkg: git.frostfs.info/TrueCloudLab/hrw
cpu: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz
                                         │      3      │                 4                  │
                                         │   sec/op    │   sec/op     vs base               │
SortHashersByValue_Typed_fnv_10-8          336.3n ± 3%   309.2n ± 2%  -8.06% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8         2.424µ ± 3%   2.306µ ± 1%  -4.87% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        22.35µ ± 1%   21.73µ ± 1%  -2.75% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8     346.6n ± 3%   347.1n ± 1%       ~ (p=0.631 n=10)
SortHashersByWeightValueTyped_fnv_100-8    2.637µ ± 6%   2.668µ ± 1%       ~ (p=0.481 n=10)
SortHashersByWeightValueTyped_fnv_1000-8   2.609µ ± 4%   2.673µ ± 1%  +2.43% (p=0.000 n=10)
geomean                                    1.875µ        1.836µ       -2.06%

                                         │       3       │                  4                   │
                                         │     B/op      │     B/op      vs base                │
SortHashersByValue_Typed_fnv_10-8             296.0 ± 0%     216.0 ± 0%  -27.03% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8          1.883Ki ± 0%   1.008Ki ± 0%  -46.47% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        16.133Ki ± 0%   8.133Ki ± 0%  -49.59% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8        296.0 ± 0%     216.0 ± 0%  -27.03% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8     1.883Ki ± 0%   1.008Ki ± 0%  -46.47% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_1000-8    1.883Ki ± 0%   1.008Ki ± 0%  -46.47% (p=0.000 n=10)
geomean                                     1.442Ki          867.8       -41.24%

                                         │     3      │                 4                  │
                                         │ allocs/op  │ allocs/op   vs base                │
SortHashersByValue_Typed_fnv_10-8          5.000 ± 0%   4.000 ± 0%  -20.00% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8         5.000 ± 0%   4.000 ± 0%  -20.00% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        5.000 ± 0%   4.000 ± 0%  -20.00% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8     5.000 ± 0%   4.000 ± 0%  -20.00% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8    5.000 ± 0%   4.000 ± 0%  -20.00% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_1000-8   5.000 ± 0%   4.000 ± 0%  -20.00% (p=0.000 n=10)
geomean                                    5.000        4.000       -20.00%
```

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

hrw.go

@@ -85,10 +85,15 @@ func SortSliceByValue(slice interface{}, hash uint64) {
 
 // SortHasherSliceByValue receives []Hasher and hash to sort by value-distance.
 func SortHasherSliceByValue[T Hasher](slice []T, hash uint64) {
-	rule := prepareHasherRule(slice)
+	if len(slice) == 0 {
-	if rule != nil {
+		return
-		sortHasherByDistance(slice, false, rule, hash)
 	}
+
+	dist := make([]uint64, len(slice))
+	for i := range dist {
+		dist[i] = distance(slice[i].Hash(), hash)
+	}
+	sortHasherByDistance(slice, false, dist)
 }
 
 // SortSliceByWeightValue received []T, weights and hash to sort by value-distance * weights
@@ -102,49 +107,28 @@ func SortSliceByWeightValue(slice interface{}, weights []float64, hash uint64) {
 
 // SortHasherSliceByWeightValue receives []Hasher, weights and hash to sort by value-distance * weights.
 func SortHasherSliceByWeightValue[T Hasher](slice []T, weights []float64, hash uint64) {
-	rule := prepareHasherRule(slice)
+	if len(slice) == 0 {
-	if rule != nil {
+		return
-		sortHasherByWeight(slice, false, rule, weights, hash)
 	}
-}
 
-// sortHasherByDistance is similar to sortByDistance but accepts slice directly.
+	if allSameF64(weights) {
-func sortHasherByDistance[T Hasher](slice []T, byIndex bool, nodes []uint64, hash uint64) {
 		dist := make([]uint64, len(slice))
 		for i := range dist {
-		dist[i] = getDistance(byIndex, i, nodes, hash)
+			dist[i] = distance(slice[i].Hash(), hash)
 		}
-
+		sortHasherByDistance(slice, false, dist)
-	s := &sorter{
-		l: len(slice),
-		swap: func(i, j int) {
-			slice[i], slice[j] = slice[j], slice[i]
-			dist[i], dist[j] = dist[j], dist[i]
-		},
-		less: func(i, j int) bool {
-			return dist[i] < dist[j]
-		},
-	}
-	sort.Sort(s)
-}
-
-// sortHasherByWeight is similar to sortByWeight but accepts slice directly.
-func sortHasherByWeight[T Hasher](slice []T, byIndex bool, nodes []uint64, weights []float64, hash uint64) {
-	// if all nodes have the same distance then sort uniformly
-	if allSameF64(weights) {
-		sortHasherByDistance(slice, byIndex, nodes, hash)
 		return
 	}
 
 	dist := make([]float64, len(slice))
 	for i := range dist {
-		d := getDistance(byIndex, i, nodes, hash)
+		d := distance(slice[i].Hash(), hash)
 		// `maxUint64 - distance` makes the shorter distance more valuable
 		// it is necessary for operation with normalized values
 		dist[i] = float64(^uint64(0)-d) * weights[i]
 	}
 
-	s := &sorter{
+	sort.Sort(&sorter{
 		l: len(slice),
 		swap: func(i, j int) {
 			slice[i], slice[j] = slice[j], slice[i]
@@ -153,8 +137,21 @@ func sortHasherByWeight[T Hasher](slice []T, byIndex bool, nodes []uint64, weigh
 		less: func(i, j int) bool {
 			return dist[i] > dist[j] // higher distance must be placed lower to be first
 		},
-	}
+	})
-	sort.Sort(s)
+}
+
+// sortHasherByDistance is similar to sortByDistance but accepts slice directly.
+func sortHasherByDistance[T Hasher](slice []T, byIndex bool, dist []uint64) {
+	sort.Sort(&sorter{
+		l: len(slice),
+		swap: func(i, j int) {
+			slice[i], slice[j] = slice[j], slice[i]
+			dist[i], dist[j] = dist[j], dist[i]
+		},
+		less: func(i, j int) bool {
+			return dist[i] < dist[j]
+		},
+	})
 }
 
 // SortSliceByIndex received []T and hash to sort by index-distance
@@ -264,18 +261,6 @@ func prepareRule(slice interface{}) []uint64 {
 	return rule
 }
 
-func prepareHasherRule[T Hasher](hashers []T) []uint64 {
-	length := len(hashers)
-	if length == 0 {
-		return nil
-	}
-	result := make([]uint64, length)
-	for i := 0; i < length; i++ {
-		result[i] = hashers[i].Hash()
-	}
-	return result
-}
-
 // ValidateWeights checks if weights are normalized between 0.0 and 1.0
 func ValidateWeights(weights []float64) error {
 	for i := range weights {