public Solution CreateInitSolution(Problem problem, Random rnd)
{
var cacheLoads = new CacheLoad[problem.C];
for (var c = 0; c < problem.C; c++)
{
var videos = new HashSet <int>();
var size = 0ul;
while (true)
{
var video = problem.Videos.Where(v => v.Size <= problem.X - size).RandomElement(rnd, false);
if (video == null)
{
break;
}
videos.Add(video.VideoId);
size += video.Size;
}
cacheLoads[c] = new CacheLoad
{
CacheId = c,
VideoIds = videos
};
}
return(new Solution
{
CacheLoads = cacheLoads
});
}
public Solution GetNeighboor(Problem problem, Solution solution, Random rnd)
{
var cacheLoads = solution.CacheLoads;
while (true)
{
var p = rnd.NextDouble();
if (p < 0.25)
{
// Add video
var cacheLoadIndex = cacheLoads.RandomIndex(rnd);
var cacheLoad = cacheLoads[cacheLoadIndex];
var size = cacheLoad.VideoIds.Select(v => problem.Videos[v].Size).Sum();
var video = problem.Videos.Where(v => v.Size <= problem.X - size).RandomElement(rnd, false);
if (video != null)
{
var newLoads = cacheLoads.ShallowClone();
newLoads[cacheLoadIndex] = new CacheLoad
{
CacheId = cacheLoad.CacheId,
VideoIds = cacheLoad.VideoIds.ToHashSet(),
};
newLoads[cacheLoadIndex].VideoIds.Add(video.VideoId);
return(new Solution {
CacheLoads = newLoads
});
}
}
else if (p < 0.5)
{
// Swap video between server and pool
var cacheLoadIndex = cacheLoads.RandomIndex(rnd);
var cacheLoad = cacheLoads[cacheLoadIndex];
if (cacheLoad.VideoIds.Count == 0)
{
continue;
}
var solVideoId = cacheLoad.VideoIds.RandomElement(rnd);
var size = cacheLoad.VideoIds.Select(v => problem.Videos[v].Size).Sum() - problem.Videos[solVideoId].Size;
var poolVideo = problem.Videos.Where(v => v.Size <= problem.X - size).RandomElement(rnd, false);
if (poolVideo == null)
{
continue;
}
var newLoads = cacheLoads.ShallowClone();
newLoads[cacheLoadIndex] = new CacheLoad
{
CacheId = cacheLoad.CacheId,
VideoIds = cacheLoad.VideoIds.ToHashSet(),
};
newLoads[cacheLoadIndex].VideoIds.Remove(solVideoId);
newLoads[cacheLoadIndex].VideoIds.Add(poolVideo.VideoId);
return(new Solution {
CacheLoads = newLoads
});
}
else if (p < 0.85)
{
// Swap video between servers
var cacheLoadIndexOne = cacheLoads.IndicesWhere(c => c.VideoIds.Count > 0).RandomElement(rnd, false);
var cacheLoadIndexTwo = cacheLoads.IndicesWhere(c => c.VideoIds.Count > 0).RandomElement(rnd, false);
if (cacheLoadIndexOne == cacheLoadIndexTwo ||
cacheLoads[cacheLoadIndexOne].VideoIds.Count == 0 ||
cacheLoads[cacheLoadIndexTwo].VideoIds.Count == 0)
{
continue;
}
var cacheLoadOne = cacheLoads[cacheLoadIndexOne];
var cacheLoadTwo = cacheLoads[cacheLoadIndexTwo];
var videoOneId = cacheLoadOne.VideoIds.RandomElement(rnd);
var videoOneSize = problem.Videos[videoOneId].Size;
var sizeOne = cacheLoadOne.VideoIds.Select(v => problem.Videos[v].Size).Sum() - videoOneSize;
var sizeTwoAll = cacheLoadTwo.VideoIds.Select(v => problem.Videos[v].Size).Sum();
var videoTwo = cacheLoadTwo.VideoIds.Select(v => problem.Videos[v]).Where(v => sizeTwoAll - v.Size + videoOneSize <= problem.X).RandomElement(rnd, false);
if (videoTwo == null)
{
continue;
}
if (sizeOne + videoTwo.Size > problem.X)
{
continue;
}
var newLoads = cacheLoads.ShallowClone();
newLoads[cacheLoadIndexOne] = new CacheLoad
{
CacheId = cacheLoadOne.CacheId,
VideoIds = cacheLoadOne.VideoIds.ToHashSet(),
};
newLoads[cacheLoadIndexTwo] = new CacheLoad
{
CacheId = cacheLoadTwo.CacheId,
VideoIds = cacheLoadTwo.VideoIds.ToHashSet(),
};
newLoads[cacheLoadIndexOne].VideoIds.Remove(videoOneId);
newLoads[cacheLoadIndexOne].VideoIds.Add(videoTwo.VideoId);
newLoads[cacheLoadIndexTwo].VideoIds.Remove(videoTwo.VideoId);
newLoads[cacheLoadIndexTwo].VideoIds.Add(videoOneId);
return(new Solution {
CacheLoads = newLoads
});
}
else
{
// Remove video
var cacheLoadIndex = cacheLoads.RandomIndex(rnd);
var cacheLoad = cacheLoads[cacheLoadIndex];
if (cacheLoad.VideoIds.Count > 0)
{
var removeVideoId = cacheLoad.VideoIds.RandomElement(rnd);
var newLoads = cacheLoads.ShallowClone();
newLoads[cacheLoadIndex] = new CacheLoad
{
CacheId = cacheLoad.CacheId,
VideoIds = cacheLoad.VideoIds.ToHashSet(),
};
newLoads[cacheLoadIndex].VideoIds.Remove(removeVideoId);
return(new Solution {
CacheLoads = newLoads
});
}
}
}
}