[#8] hrw: Inline swap() when slice is known

```
goos: linux
goarch: amd64
pkg: git.frostfs.info/TrueCloudLab/hrw
cpu: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz
                                         │      2      │                 3                  │
                                         │   sec/op    │   sec/op     vs base               │
SortHashersByValue_Typed_fnv_10-8          368.5n ± 2%   336.3n ± 3%  -8.75% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8         2.411µ ± 4%   2.424µ ± 3%       ~ (p=0.853 n=10)
SortHashersByValue_Typed_fnv_1000-8        22.19µ ± 2%   22.35µ ± 1%       ~ (p=0.247 n=10)
SortHashersByWeightValueTyped_fnv_10-8     364.3n ± 2%   346.6n ± 3%  -4.86% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8    2.541µ ± 3%   2.637µ ± 6%       ~ (p=0.055 n=10)
SortHashersByWeightValueTyped_fnv_1000-8   2.483µ ± 1%   2.609µ ± 4%  +5.07% (p=0.003 n=10)
geomean                                    1.888µ        1.875µ       -0.71%

                                         │      2       │                  3                  │
                                         │     B/op     │     B/op      vs base               │
SortHashersByValue_Typed_fnv_10-8            312.0 ± 0%     296.0 ± 0%  -5.13% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8         1.898Ki ± 0%   1.883Ki ± 0%  -0.82% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        16.15Ki ± 0%   16.13Ki ± 0%  -0.10% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8       312.0 ± 0%     296.0 ± 0%  -5.13% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8    1.898Ki ± 0%   1.883Ki ± 0%  -0.82% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_1000-8   1.898Ki ± 0%   1.883Ki ± 0%  -0.82% (p=0.000 n=10)
geomean                                    1.474Ki        1.442Ki       -2.16%

                                         │     2      │                 3                  │
                                         │ allocs/op  │ allocs/op   vs base                │
SortHashersByValue_Typed_fnv_10-8          6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_100-8         6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=10)
SortHashersByValue_Typed_fnv_1000-8        6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_10-8     6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_100-8    6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=10)
SortHashersByWeightValueTyped_fnv_1000-8   6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=10)
geomean                                    6.000        5.000       -16.67%
```

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

hrw.go

@@ -87,10 +87,7 @@ func SortSliceByValue(slice interface{}, hash uint64) {
 func SortHasherSliceByValue[T Hasher](slice []T, hash uint64) {
 	rule := prepareHasherRule(slice)
 	if rule != nil {
-		swap := func(i, j int) {
+		sortHasherByDistance(slice, false, rule, hash)
-			slice[i], slice[j] = slice[j], slice[i]
-		}
-		sortByDistance(len(rule), false, rule, hash, swap)
 	}
 }
 
@@ -107,11 +104,57 @@ func SortSliceByWeightValue(slice interface{}, weights []float64, hash uint64) {
 func SortHasherSliceByWeightValue[T Hasher](slice []T, weights []float64, hash uint64) {
 	rule := prepareHasherRule(slice)
 	if rule != nil {
-		swap := func(i, j int) {
+		sortHasherByWeight(slice, false, rule, weights, hash)
+	}
+}
+
+// sortHasherByDistance is similar to sortByDistance but accepts slice directly.
+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)
+	}
+
+	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]
+		},
 	}
-		sortByWeight(len(slice), false, rule, weights, hash, swap)
+	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)
+		// `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{
+		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] // higher distance must be placed lower to be first
+		},
+	}
+	sort.Sort(s)
 }
 
 // SortSliceByIndex received []T and hash to sort by index-distance