aj/CutList
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

perf: Add lower-bound pruning to ExhaustiveFitEngine

Browse Source 
Precompute suffix sums of remaining item volumes and use them
to prune branches that cannot beat the current best solution.
Raises DefaultMaxItems from 20 to 25 (~84ms worst case).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
AJ Isaacs
2026-02-09 22:12:28 -05:00
parent c23c92e852
commit 8926d44969
1 changed files with 27 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
CutList.Core/Nesting/ExhaustiveFitEngine.cs
View File

@@ -9,9 +9,9 @@ namespace CutList.Core.Nesting
{
/// <summary>
/// Default maximum number of items before falling back to AdvancedFitEngine.
/// Testing showed 20 items is safe (~100ms worst case), while 21+ can take seconds.
/// Testing showed 25 items is safe (~84ms worst case), while 30+ can take seconds.
/// </summary>
public const int DefaultMaxItems = 20;
public const int DefaultMaxItems = 25;
private readonly IEngine _fallbackEngine;
private readonly int _maxItems;
@@ -67,7 +67,15 @@ namespace CutList.Core.Nesting
BinCount = 0
};
Search(sortedItems, 0, currentState, bestSolution, request);
// Precompute suffix sums of item lengths (including spacing per item)
// for lower-bound pruning. suffixVolume[i] = total volume of items[i..n-1].
var suffixVolume = new double[sortedItems.Count + 1];
for (int i = sortedItems.Count - 1; i >= 0; i--)
{
suffixVolume[i] = suffixVolume[i + 1] + sortedItems[i].Length + request.Spacing;
}
Search(sortedItems, 0, currentState, bestSolution, request, suffixVolume);
// Build result from best solution
var result = new PackResult();
@@ -101,7 +109,8 @@ namespace CutList.Core.Nesting
int itemIndex,
SearchState current,
SearchState best,
PackingRequest request)
PackingRequest request,
double[] suffixVolume)
{
// All items placed - check if this is better
if (itemIndex >= items.Count)
@@ -123,6 +132,18 @@ namespace CutList.Core.Nesting
if (current.BinCount >= request.MaxBinCount)
return;
// Lower-bound pruning: remaining items need at least this many additional bins
double remainingVolume = suffixVolume[itemIndex];
double availableInExisting = 0;
for (int b = 0; b < current.Bins.Count; b++)
{
availableInExisting += request.StockLength - GetBinUsedLength(current.Bins[b], request.Spacing);
}
double overflow = remainingVolume - availableInExisting;
int additionalBinsNeeded = overflow > 0 ? (int)Math.Ceiling(overflow / request.StockLength) : 0;
if (current.BinCount + additionalBinsNeeded >= best.BinCount)
return;
var item = items[itemIndex];
// Symmetry breaking: if this item has the same length as the previous item,
@@ -148,7 +169,7 @@ namespace CutList.Core.Nesting
current.Bins[i].Add(item);
var prevBinIndex = current.LastBinIndexUsed;
current.LastBinIndexUsed = i;
Search(items, itemIndex + 1, current, best, request);
Search(items, itemIndex + 1, current, best, request, suffixVolume);
current.LastBinIndexUsed = prevBinIndex;
current.Bins[i].RemoveAt(current.Bins[i].Count - 1);
}
@@ -162,7 +183,7 @@ namespace CutList.Core.Nesting
current.BinCount++;
var prevBinIndex = current.LastBinIndexUsed;
current.LastBinIndexUsed = newBinIndex;
Search(items, itemIndex + 1, current, best, request);
Search(items, itemIndex + 1, current, best, request, suffixVolume);
current.LastBinIndexUsed = prevBinIndex;
current.Bins.RemoveAt(current.Bins.Count - 1);
current.BinCount--;