feat: add optional M98 part sub-programs to Cincinnati post processor

Each unique part geometry (drawing + rotation) is written once as a
reusable sub-program called via M98, reducing output size for nests
with repeated parts. G92 coordinate repositioning handles per-instance
plate placement with restore after each call. Cut-offs remain inline.

Controlled by UsePartSubprograms (default false) and PartSubprogramStart
config properties.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Posts.Cincinnati/CincinnatiPartSubprogramWriter.cs

@@ -0,0 +1,124 @@
+using System.Collections.Generic;
+using System.IO;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+
+namespace OpenNest.Posts.Cincinnati;
+
+/// <summary>
+/// Writes a Cincinnati-format part sub-program definition.
+/// Each sub-program contains the complete cutting sequence for one unique part geometry
+/// (drawing + rotation), with coordinates normalized to origin (0,0).
+/// Called via M98 from sheet sub-programs.
+/// </summary>
+public sealed class CincinnatiPartSubprogramWriter
+{
+    private readonly CincinnatiPostConfig _config;
+    private readonly CincinnatiFeatureWriter _featureWriter;
+
+    public CincinnatiPartSubprogramWriter(CincinnatiPostConfig config)
+    {
+        _config = config;
+        _featureWriter = new CincinnatiFeatureWriter(config);
+    }
+
+    /// <summary>
+    /// Writes a complete part sub-program for the given normalized program.
+    /// The program coordinates must already be normalized to origin (0,0).
+    /// </summary>
+    public void Write(TextWriter w, Program normalizedProgram, string drawingName,
+        int subNumber, string libraryFile, double sheetDiagonal)
+    {
+        var features = SplitFeatures(normalizedProgram.Codes);
+        if (features.Count == 0)
+            return;
+
+        w.WriteLine("(*****************************************************)");
+        w.WriteLine($":{subNumber}");
+        w.WriteLine(CoordinateFormatter.Comment($"PART: {drawingName}"));
+
+        for (var i = 0; i < features.Count; i++)
+        {
+            var codes = features[i];
+            var featureNumber = i == 0
+                ? _config.FeatureLineNumberStart
+                : 1000 + i + 1;
+            var cutDistance = ComputeCutDistance(codes);
+
+            var ctx = new FeatureContext
+            {
+                Codes = codes,
+                FeatureNumber = featureNumber,
+                PartName = drawingName,
+                IsFirstFeatureOfPart = false,
+                IsLastFeatureOnSheet = i == features.Count - 1,
+                IsSafetyHeadraise = false,
+                IsExteriorFeature = false,
+                LibraryFile = libraryFile,
+                CutDistance = cutDistance,
+                SheetDiagonal = sheetDiagonal
+            };
+
+            _featureWriter.Write(w, ctx);
+        }
+
+        w.WriteLine("G0X0Y0");
+        w.WriteLine($"M99(END OF {drawingName})");
+    }
+
+    /// <summary>
+    /// Creates a sub-program key for matching parts to their sub-programs.
+    /// </summary>
+    internal static (int drawingId, long rotationKey) SubprogramKey(Part part) =>
+        (part.BaseDrawing.Id, (long)System.Math.Round(part.Rotation * 1e6));
+
+    internal static List<List<ICode>> SplitFeatures(List<ICode> codes)
+    {
+        var features = new List<List<ICode>>();
+        List<ICode> current = null;
+
+        foreach (var code in codes)
+        {
+            if (code is RapidMove)
+            {
+                if (current != null)
+                    features.Add(current);
+                current = new List<ICode> { code };
+            }
+            else
+            {
+                current ??= new List<ICode>();
+                current.Add(code);
+            }
+        }
+
+        if (current != null && current.Count > 0)
+            features.Add(current);
+
+        return features;
+    }
+
+    internal static double ComputeCutDistance(List<ICode> codes)
+    {
+        var distance = 0.0;
+        var currentPos = Vector.Zero;
+
+        foreach (var code in codes)
+        {
+            if (code is RapidMove rapid)
+                currentPos = rapid.EndPoint;
+            else if (code is LinearMove linear)
+            {
+                distance += currentPos.DistanceTo(linear.EndPoint);
+                currentPos = linear.EndPoint;
+            }
+            else if (code is ArcMove arc)
+            {
+                distance += currentPos.DistanceTo(arc.EndPoint);
+                currentPos = arc.EndPoint;
+            }
+        }
+
+        return distance;
+    }
+}

OpenNest.Posts.Cincinnati/CincinnatiPostConfig.cs

@@ -126,6 +126,20 @@ namespace OpenNest.Posts.Cincinnati
         /// </summary>
         public int SheetSubprogramStart { get; set; } = 101;
 
+        /// <summary>
+        /// Gets or sets whether to use M98 sub-programs for part geometry.
+        /// When enabled, each unique part geometry is written as a reusable sub-program
+        /// called via M98, reducing output size for nests with repeated parts.
+        /// Default: false
+        /// </summary>
+        public bool UsePartSubprograms { get; set; } = false;
+
+        /// <summary>
+        /// Gets or sets the starting sub-program number for part geometry sub-programs.
+        /// Default: 200
+        /// </summary>
+        public int PartSubprogramStart { get; set; } = 200;
+
         /// <summary>
         /// Gets or sets the subprogram number for variable declarations.
         /// Default: 100

OpenNest.Posts.Cincinnati/CincinnatiPostProcessor.cs

@@ -68,17 +68,49 @@ namespace OpenNest.Posts.Cincinnati
                 .Where(p => p.Parts.Count > 0)
                 .ToList();
 
-            // 3. Create writers
+            // 3. Build part sub-program registry (if enabled)
+            Dictionary<(int, long), int> partSubprograms = null;
+            List<(int subNum, string name, Program program)> subprogramEntries = null;
+
+            if (Config.UsePartSubprograms)
+            {
+                partSubprograms = new Dictionary<(int, long), int>();
+                subprogramEntries = new List<(int, string, Program)>();
+                var nextSubNum = Config.PartSubprogramStart;
+
+                foreach (var plate in plates)
+                {
+                    foreach (var part in plate.Parts)
+                    {
+                        if (part.BaseDrawing.IsCutOff) continue;
+                        var key = CincinnatiPartSubprogramWriter.SubprogramKey(part);
+                        if (!partSubprograms.ContainsKey(key))
+                        {
+                            var subNum = nextSubNum++;
+                            partSubprograms[key] = subNum;
+
+                            // Create normalized program at origin
+                            var pgm = part.Program.Clone() as Program;
+                            var bbox = pgm.BoundingBox();
+                            pgm.Offset(-bbox.Location.X, -bbox.Location.Y);
+
+                            subprogramEntries.Add((subNum, part.BaseDrawing.Name, pgm));
+                        }
+                    }
+                }
+            }
+
+            // 4. Create writers
             var preamble = new CincinnatiPreambleWriter(Config);
             var sheetWriter = new CincinnatiSheetWriter(Config, vars);
 
-            // 4. Build material description from first plate
+            // 5. Build material description from first plate
             var material = plates.FirstOrDefault()?.Material;
             var materialDesc = material != null
                 ? $"{material.Name}{(string.IsNullOrEmpty(material.Grade) ? "" : $", {material.Grade}")}"
                 : "";
 
-            // 5. Write to stream
+            // 6. Write to stream
             using var writer = new StreamWriter(outputStream, Encoding.UTF8, 1024, leaveOpen: true);
 
             // Main program
@@ -92,7 +124,25 @@ namespace OpenNest.Posts.Cincinnati
             {
                 var sheetIndex = i + 1;
                 var subNumber = Config.SheetSubprogramStart + i;
-                sheetWriter.Write(writer, plates[i], nest.Name ?? "NEST", sheetIndex, subNumber);
+                sheetWriter.Write(writer, plates[i], nest.Name ?? "NEST", sheetIndex, subNumber,
+                    partSubprograms);
+            }
+
+            // Part sub-programs (if enabled)
+            if (subprogramEntries != null)
+            {
+                var partSubWriter = new CincinnatiPartSubprogramWriter(Config);
+                var firstPlate = plates.FirstOrDefault();
+                var sheetDiagonal = firstPlate != null
+                    ? System.Math.Sqrt(firstPlate.Size.Width * firstPlate.Size.Width
+                        + firstPlate.Size.Length * firstPlate.Size.Length)
+                    : 100.0;
+
+                foreach (var (subNum, name, pgm) in subprogramEntries)
+                {
+                    partSubWriter.Write(writer, pgm, name, subNum,
+                        Config.DefaultLibraryFile ?? "", sheetDiagonal);
+                }
             }
 
             writer.Flush();

OpenNest.Posts.Cincinnati/CincinnatiSheetWriter.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Text;
 using OpenNest.CNC;
 using OpenNest.Geometry;
 
@@ -9,7 +10,7 @@ namespace OpenNest.Posts.Cincinnati;
 
 /// <summary>
 /// Emits one Cincinnati-format sheet subprogram per plate.
-/// Splits each part's codes at RapidMove boundaries to handle multi-contour parts.
+/// Supports two modes: inline features (default) or M98 sub-program calls per part.
 /// </summary>
 public sealed class CincinnatiSheetWriter
 {
@@ -29,7 +30,12 @@ public sealed class CincinnatiSheetWriter
     /// <summary>
     /// Writes a complete sheet subprogram for the given plate.
     /// </summary>
-    public void Write(TextWriter w, Plate plate, string nestName, int sheetIndex, int subNumber)
+    /// <param name="partSubprograms">
+    /// Optional mapping of (drawingId, rotationKey) to sub-program number.
+    /// When provided, non-cutoff parts are emitted as M98 calls instead of inline features.
+    /// </param>
+    public void Write(TextWriter w, Plate plate, string nestName, int sheetIndex, int subNumber,
+        Dictionary<(int, long), int> partSubprograms = null)
     {
         if (plate.Parts.Count == 0)
             return;
@@ -78,7 +84,120 @@ public sealed class CincinnatiSheetWriter
 
         var allParts = nonCutoffParts.Concat(cutoffParts).ToList();
 
-        // 4. Multi-contour splitting
+        // 4. Emit parts
+        if (partSubprograms != null)
+            WritePartsWithSubprograms(w, allParts, libraryFile, sheetDiagonal, partSubprograms);
+        else
+            WritePartsInline(w, allParts, libraryFile, sheetDiagonal);
+
+        // 5. Footer
+        w.WriteLine("M42");
+        w.WriteLine("G0X0Y0");
+        if (_config.PalletExchange != PalletMode.None)
+            w.WriteLine($"N{sheetIndex + 1}M50");
+        w.WriteLine($"M99(END OF {nestName}.{sheetIndex:D3})");
+    }
+
+    private void WritePartsWithSubprograms(TextWriter w, List<Part> allParts,
+        string libraryFile, double sheetDiagonal,
+        Dictionary<(int, long), int> partSubprograms)
+    {
+        var lastPartName = "";
+        var featureIndex = 0;
+
+        for (var p = 0; p < allParts.Count; p++)
+        {
+            var part = allParts[p];
+            var partName = part.BaseDrawing.Name;
+            var isNewPart = partName != lastPartName;
+            var isSafetyHeadraise = isNewPart && lastPartName != "";
+            var isLastPart = p == allParts.Count - 1;
+
+            var key = CincinnatiPartSubprogramWriter.SubprogramKey(part);
+            partSubprograms.TryGetValue(key, out var subNum);
+            var hasSubprogram = !part.BaseDrawing.IsCutOff && subNum != 0;
+
+            if (hasSubprogram)
+            {
+                WriteSubprogramCall(w, part, subNum, featureIndex, partName,
+                    isSafetyHeadraise, isLastPart);
+                featureIndex++;
+            }
+            else
+            {
+                // Inline features for cutoffs or parts without sub-programs
+                var features = SplitPartFeatures(part);
+                for (var f = 0; f < features.Count; f++)
+                {
+                    var featureNumber = featureIndex == 0
+                        ? _config.FeatureLineNumberStart
+                        : 1000 + featureIndex + 1;
+
+                    var isLastFeature = isLastPart && f == features.Count - 1;
+                    var cutDistance = ComputeCutDistance(features[f]);
+
+                    var ctx = new FeatureContext
+                    {
+                        Codes = features[f],
+                        FeatureNumber = featureNumber,
+                        PartName = partName,
+                        IsFirstFeatureOfPart = isNewPart && f == 0,
+                        IsLastFeatureOnSheet = isLastFeature,
+                        IsSafetyHeadraise = isSafetyHeadraise && f == 0,
+                        IsExteriorFeature = false,
+                        LibraryFile = libraryFile,
+                        CutDistance = cutDistance,
+                        SheetDiagonal = sheetDiagonal
+                    };
+
+                    _featureWriter.Write(w, ctx);
+                    featureIndex++;
+                }
+            }
+
+            lastPartName = partName;
+        }
+    }
+
+    private void WriteSubprogramCall(TextWriter w, Part part, int subNum,
+        int featureIndex, string partName, bool isSafetyHeadraise, bool isLastPart)
+    {
+        // Safety headraise before rapid to new part
+        if (isSafetyHeadraise && _config.SafetyHeadraiseDistance.HasValue)
+            w.WriteLine($"M47 P{_config.SafetyHeadraiseDistance.Value}(Safety Headraise)");
+
+        // Rapid to part position (bounding box lower-left)
+        var featureNumber = featureIndex == 0
+            ? _config.FeatureLineNumberStart
+            : 1000 + featureIndex + 1;
+
+        var sb = new StringBuilder();
+        if (_config.UseLineNumbers)
+            sb.Append($"N{featureNumber}");
+        sb.Append($"G0X{_fmt.FormatCoord(part.Left)}Y{_fmt.FormatCoord(part.Bottom)}");
+        w.WriteLine(sb.ToString());
+
+        // Part name comment
+        w.WriteLine(CoordinateFormatter.Comment($"PART: {partName}"));
+
+        // Set local coordinate system at part position
+        w.WriteLine("G92X0Y0");
+
+        // Call part sub-program
+        w.WriteLine($"M98P{subNum}({partName})");
+
+        // Restore sheet coordinate system
+        w.WriteLine($"G92X{_fmt.FormatCoord(part.Left)}Y{_fmt.FormatCoord(part.Bottom)}");
+
+        // Head raise (unless last part on sheet)
+        if (!isLastPart)
+            w.WriteLine("M47");
+    }
+
+    private void WritePartsInline(TextWriter w, List<Part> allParts,
+        string libraryFile, double sheetDiagonal)
+    {
+        // Multi-contour splitting
         var features = new List<(Part part, List<ICode> codes)>();
         foreach (var part in allParts)
         {
@@ -101,7 +220,7 @@ public sealed class CincinnatiSheetWriter
                 features.Add((part, current));
         }
 
-        // 5. Emit features
+        // Emit features
         var lastPartName = "";
         for (var i = 0; i < features.Count; i++)
         {
@@ -111,12 +230,10 @@ public sealed class CincinnatiSheetWriter
             var isSafetyHeadraise = partName != lastPartName && lastPartName != "";
             var isLastFeature = i == features.Count - 1;
 
-            // Feature numbering: first = FeatureLineNumberStart, then 1002, 1003, etc.
             var featureNumber = i == 0
                 ? _config.FeatureLineNumberStart
                 : 1000 + i + 1;
 
-            // Compute cut distance for this feature
             var cutDistance = ComputeCutDistance(codes);
 
             var ctx = new FeatureContext
@@ -136,13 +253,32 @@ public sealed class CincinnatiSheetWriter
             _featureWriter.Write(w, ctx);
             lastPartName = partName;
         }
+    }
 
-        // 6. Footer
-        w.WriteLine("M42");
-        w.WriteLine("G0X0Y0");
-        if (_config.PalletExchange != PalletMode.None)
-            w.WriteLine($"N{sheetIndex + 1}M50");
-        w.WriteLine($"M99(END OF {nestName}.{sheetIndex:D3})");
+    private static List<List<ICode>> SplitPartFeatures(Part part)
+    {
+        var features = new List<List<ICode>>();
+        List<ICode> current = null;
+
+        foreach (var code in part.Program.Codes)
+        {
+            if (code is RapidMove)
+            {
+                if (current != null)
+                    features.Add(current);
+                current = new List<ICode> { code };
+            }
+            else
+            {
+                current ??= new List<ICode>();
+                current.Add(code);
+            }
+        }
+
+        if (current != null && current.Count > 0)
+            features.Add(current);
+
+        return features;
     }
 
     private static double ComputeCutDistance(List<ICode> codes)

OpenNest.Tests/Cincinnati/CincinnatiPostProcessorTests.cs

@@ -139,6 +139,163 @@ public class CincinnatiPostProcessorTests
         Assert.Equal("CL940", post.Config.ConfigurationName);
     }
 
+    [Fact]
+    public void Post_WithPartSubprograms_WritesM98Calls()
+    {
+        var nest = CreateTestNest();
+        var config = new CincinnatiPostConfig
+        {
+            PostedAccuracy = 4,
+            UsePartSubprograms = true,
+            PartSubprogramStart = 200
+        };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+
+        // Sheet should contain M98 call to part sub-program
+        Assert.Contains("M98P200", output);
+
+        // Should have G92 for local coordinate positioning
+        Assert.Contains("G92X0Y0", output);
+
+        // Part sub-program definition
+        Assert.Contains(":200", output);
+        Assert.Contains("G84", output);
+
+        // Sub-program ends with G0X0Y0 and M99
+        Assert.Contains("G0X0Y0", output);
+        Assert.Contains("M99(END OF Square)", output);
+
+        // G92 restore after M98 call
+        Assert.Contains("G92X", output);
+    }
+
+    [Fact]
+    public void Post_WithPartSubprograms_ReusesSameSubprogram()
+    {
+        var nest = new Nest("TestNest");
+        var drawing = new Drawing("Square", CreateSquareProgram());
+        var plate = new Plate(48, 96);
+        plate.Parts.Add(new Part(drawing, new Vector(5, 5)));
+        plate.Parts.Add(new Part(drawing, new Vector(20, 5)));
+        nest.Plates.Add(plate);
+
+        var config = new CincinnatiPostConfig
+        {
+            PostedAccuracy = 4,
+            UsePartSubprograms = true,
+            PartSubprogramStart = 200
+        };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+
+        // Both parts should call the same sub-program
+        var m98Count = System.Text.RegularExpressions.Regex.Matches(output, "M98P200").Count;
+        Assert.Equal(2, m98Count);
+
+        // Only one sub-program definition
+        var subDefCount = System.Text.RegularExpressions.Regex.Matches(output, ":200").Count;
+        Assert.Equal(1, subDefCount);
+    }
+
+    [Fact]
+    public void Post_WithPartSubprograms_DifferentRotationsGetSeparateSubprograms()
+    {
+        var nest = new Nest("TestNest");
+        var drawing = new Drawing("Square", CreateSquareProgram());
+        var plate = new Plate(48, 96);
+
+        var part1 = new Part(drawing, new Vector(5, 5));
+        plate.Parts.Add(part1);
+
+        var part2 = new Part(drawing, new Vector(20, 5));
+        part2.Rotate(System.Math.PI / 2); // 90 degrees
+        plate.Parts.Add(part2);
+
+        nest.Plates.Add(plate);
+
+        var config = new CincinnatiPostConfig
+        {
+            PostedAccuracy = 4,
+            UsePartSubprograms = true,
+            PartSubprogramStart = 200
+        };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+
+        // Should have two different sub-programs
+        Assert.Contains(":200", output);
+        Assert.Contains(":201", output);
+        Assert.Contains("M98P200", output);
+        Assert.Contains("M98P201", output);
+    }
+
+    [Fact]
+    public void Post_WithPartSubprograms_CutoffsAreInline()
+    {
+        var nest = new Nest("TestNest");
+        var drawing = new Drawing("Square", CreateSquareProgram());
+        var cutoffDrawing = new Drawing("CutOff", CreateSquareProgram()) { IsCutOff = true };
+
+        var plate = new Plate(48, 96);
+        plate.Parts.Add(new Part(drawing, new Vector(5, 5)));
+        plate.Parts.Add(new Part(cutoffDrawing, new Vector(0, 30)));
+        nest.Plates.Add(plate);
+
+        var config = new CincinnatiPostConfig
+        {
+            PostedAccuracy = 4,
+            UsePartSubprograms = true,
+            PartSubprogramStart = 200
+        };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+
+        // Regular part uses sub-program
+        Assert.Contains("M98P200", output);
+        Assert.Contains(":200", output);
+
+        // Cutoff should NOT have its own sub-program
+        Assert.DoesNotContain(":201", output);
+    }
+
+    [Fact]
+    public void Post_WithPartSubprograms_ConfigRoundTrips()
+    {
+        var config = new CincinnatiPostConfig
+        {
+            UsePartSubprograms = true,
+            PartSubprogramStart = 300
+        };
+
+        var opts = new JsonSerializerOptions
+        {
+            WriteIndented = true,
+            Converters = { new JsonStringEnumConverter() }
+        };
+        var json = JsonSerializer.Serialize(config, opts);
+        var deserialized = JsonSerializer.Deserialize<CincinnatiPostConfig>(json, opts);
+
+        Assert.True(deserialized.UsePartSubprograms);
+        Assert.Equal(300, deserialized.PartSubprogramStart);
+    }
+
     private static Nest CreateTestNest()
     {
         var nest = new Nest("TestNest");