From 0e3bf3ccaaccc7056c9f9ed45e5c51a9a043237d Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Tue, 10 Mar 2026 23:19:42 -0400
Subject: [PATCH] feat: try fewer rows in FillRecursive when remainder strip
 yields more parts

When the greedy maximum-row tiling leaves a thin remainder, tries removing
the last row and re-filling the larger strip. Picks whichever total is
higher. Fixes cases where e.g. 4 rows + 11 remainder = 47 beats 5 rows = 45.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 OpenNest.Engine/FillLinear.cs | 41 +++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/OpenNest.Engine/FillLinear.cs b/OpenNest.Engine/FillLinear.cs
index 431947d..c6cae63 100644
--- a/OpenNest.Engine/FillLinear.cs
+++ b/OpenNest.Engine/FillLinear.cs
@@ -338,15 +338,23 @@ namespace OpenNest
                 var rowPattern = new Pattern();
                 rowPattern.Parts.AddRange(result);
                 rowPattern.UpdateBounds();
-                var gridResult = FillRecursive(rowPattern, PerpendicularAxis(direction), depth + 1);
+                var perpAxis = PerpendicularAxis(direction);
+                var gridResult = FillRecursive(rowPattern, perpAxis, depth + 1);
 
                 // Fill the remaining strip (after the last full row/column)
                 // with individual parts from the seed pattern.
-                var remaining = FillRemainingStrip(gridResult, pattern, PerpendicularAxis(direction), direction);
+                var remaining = FillRemainingStrip(gridResult, pattern, perpAxis, direction);
 
                 if (remaining.Count > 0)
                     gridResult.AddRange(remaining);
 
+                // Try one fewer row/column — the larger remainder strip may
+                // fit more parts than the extra row contained.
+                var fewerResult = TryFewerRows(gridResult, rowPattern, pattern, perpAxis, direction);
+
+                if (fewerResult != null && fewerResult.Count > gridResult.Count)
+                    return fewerResult;
+
                 return gridResult;
             }
 
@@ -359,6 +367,35 @@ namespace OpenNest
             return result;
         }
 
+        /// <summary>
+        /// Tries removing the last row/column from the grid and re-filling the
+        /// larger remainder strip. Returns null if this doesn't improve the total.
+        /// </summary>
+        private List<Part> TryFewerRows(
+            List<Part> fullResult, Pattern rowPattern, Pattern seedPattern,
+            NestDirection tiledAxis, NestDirection primaryAxis)
+        {
+            var rowPartCount = rowPattern.Parts.Count;
+
+            // Need at least 2 rows for this to make sense (remove 1, keep 1+).
+            if (fullResult.Count < rowPartCount * 2)
+                return null;
+
+            // Remove the last row's worth of parts.
+            var fewerParts = new List<Part>(fullResult.Count - rowPartCount);
+
+            for (var i = 0; i < fullResult.Count - rowPartCount; i++)
+                fewerParts.Add(fullResult[i]);
+
+            var remaining = FillRemainingStrip(fewerParts, seedPattern, tiledAxis, primaryAxis);
+
+            if (remaining.Count <= rowPartCount)
+                return null;
+
+            fewerParts.AddRange(remaining);
+            return fewerParts;
+        }
+
         /// <summary>
         /// After tiling full rows/columns, fills the remaining strip with individual
         /// parts. The strip is the leftover space along the tiled axis between the