frostfs-sdk-csharp/src/FrostFS.SDK.Client/Models/Netmap/Placement/Tools.cs

using System;
using System.Collections.Generic;
using System.Linq;

using static FrostFS.SDK.FrostFsNetmapSnapshot;

namespace FrostFS.SDK.Client.Models.Netmap.Placement;

public static class Tools
{
    internal static ulong Distance(ulong x, ulong y)
    {
        var acc = x ^ y;
        acc ^= acc >> 33;
        acc *= 0xff51afd7ed558ccd;
        acc ^= acc >> 33;
        acc *= 0xc4ceb9fe1a85ec53;
        acc ^= acc >> 33;

        return acc;
    }

    internal static double ReverceNormalize(double r, double w)
    {
        return (r + 1) / (w + 1);
    }

    internal static double Normalize(double r, double w)
    {
        if (r == 0)
        {
            return 0;
        }

        var x = w / r;
        return x / (1 + x);
    }

    internal static void AppendWeightsTo(FrostFsNodeInfo[] nodes, Func<FrostFsNodeInfo, double> wf, ref double[] weights)
    {
        if (weights.Length < nodes.Length)
        {
            weights = new double[nodes.Length];
        }

        for (int i = 0; i < nodes.Length; i++)
        {
            weights[i] = wf(nodes[i]);
        }
    }

    internal static List<T> SortHasherSliceByWeightValue<T>(List<T> nodes, Span<double> weights, ulong hash) where T : IHasher
    {
        if (nodes.Count == 0)
        {
            return nodes;
        }

        var allEquals = true;

        if (weights.Length > 1)
        {
            for (int i = 1; i < weights.Length; i++)
            {
                if (weights[i] != weights[0])
                {
                    allEquals = false;
                    break;
                }
            }
        }

        var dist = new double[nodes.Count];

        if (allEquals)
        {
            for (int i = 0; i < dist.Length; i++)
            {
                var x = nodes[i].Hash();
                dist[i] = Distance(x, hash);
            }

            return SortHasherByDistance(nodes, dist, true);
        }

        for (int i = 0; i < dist.Length; i++)
        {
            var d = Distance(nodes[i].Hash(), hash);
            dist[i] = (ulong.MaxValue - d) * weights[i];
        }

        return SortHasherByDistance(nodes, dist, false);
    }

    internal static List<T> SortHasherByDistance<T, N>(List<T> nodes, N[] dist, bool asc)
    {
        IndexedValue<T, N>[] indexes = new IndexedValue<T, N>[nodes.Count];
        for (int i = 0; i < dist.Length; i++)
        {
            indexes[i] = new IndexedValue<T, N>() { nodeInfo = nodes[i], dist = dist[i] };
        }

        if (asc)
        {
            return new List<T>(indexes
                .OrderBy(x => x.dist)
                .Select(x => x.nodeInfo).ToArray());
        }
        else
        {
            return new List<T>(indexes
                .OrderByDescending(x => x.dist)
                .Select(x => x.nodeInfo));
        }
    }

    internal static Func<FrostFsNodeInfo, double> DefaultWeightFunc(IReadOnlyList<FrostFsNodeInfo> nodes)
    {
        MeanAgg mean = new();
        MinAgg minV = new();

        foreach (var node in nodes)
        {
            mean.Add(node.GetCapacity());
            minV.Add(node.Price);
        }

        return NewWeightFunc(
            NewSigmoidNorm(mean.Compute()),
            NewReverseMinNorm(minV.Compute()));
    }

    private struct IndexedValue<T, N>
    {
        internal T nodeInfo;
        internal N dist;
    }
}