Performance improvements and .Net 9 support (UglyToad#1116)

* Refactor letter handling by orientation for efficiency

Improved the processing of letters based on their text orientation by preallocating separate lists for each orientation (horizontal, rotate270, rotate180, rotate90, and other). This change reduces multiple calls to `GetWords` and minimizes enumerations and allocations, enhancing performance and readability. Each letter is now added to the appropriate list in a single iteration over the `letters` collection.

* Update target frameworks to include net9.0

Expanded compatibility in `UglyToad.PdfPig.csproj` by adding
`net9.0` to the list of target frameworks, alongside existing
versions.

* Add .NET 9.0 support and refactor key components

Updated project files for UglyToad.PdfPig to target .NET 9.0, enhancing compatibility with the latest framework features.

Refactored `GetBlocks` in `DocstrumBoundingBoxes.cs` for improved input handling and performance.

Significantly optimized `NearestNeighbourWordExtractor.cs` by replacing multiple lists with an array of buckets and implementing parallel processing for better efficiency.

Consistent updates across `Fonts`, `Tests`, `Tokenization`, and `Tokens` project files to include .NET 9.0 support.

* Improve null checks and optimize list handling

- Updated null check for `words` in `DocstrumBoundingBoxes.cs` for better readability and performance.
- Changed from `ToList()` to `ToArray()` to avoid unnecessary enumeration.
- Added `results.TrimExcess()` in `NearestNeighbourWordExtractor.cs` to optimize memory usage.

---------

Co-authored-by: Chuck Beasley <CBeasley@kilpatricktownsend.com>

Author: chuckbeasley

src/UglyToad.PdfPig.Core/UglyToad.PdfPig.Core.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0;net9.0</TargetFrameworks>
     <LangVersion>12</LangVersion>
     <Version>0.1.12-alpha001</Version>
     <IsTestProject>False</IsTestProject>

src/UglyToad.PdfPig.DocumentLayoutAnalysis/PageSegmenter/DocstrumBoundingBoxes.cs

@@ -48,12 +48,19 @@ public DocstrumBoundingBoxes(DocstrumBoundingBoxesOptions options)
         /// <returns>The <see cref="TextBlock"/>s generated by the document spectrum method.</returns>
         public IReadOnlyList<TextBlock> GetBlocks(IEnumerable<Word> words)
         {
-            if (words?.Any() != true)
+            if (words is null)
             {
                 return Array.Empty<TextBlock>();
             }
 
-            return GetBlocks(words.ToList(),
+            // Avoid multiple enumeration and unnecessary ToArray() if already a list
+            var wordList = words as IReadOnlyList<Word> ?? words.ToArray();
+            if (wordList.Count == 0)
+            {
+                return Array.Empty<TextBlock>();
+            }
+
+            return GetBlocks(wordList,
                 options.WithinLineBounds, options.WithinLineMultiplier, options.WithinLineBinSize,
                 options.BetweenLineBounds, options.BetweenLineMultiplier, options.BetweenLineBinSize,
                 options.AngularDifferenceBounds,

src/UglyToad.PdfPig.DocumentLayoutAnalysis/UglyToad.PdfPig.DocumentLayoutAnalysis.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0;net9.0</TargetFrameworks>
     <LangVersion>12</LangVersion>
     <Version>0.1.12-alpha001</Version>
     <IsTestProject>False</IsTestProject>

src/UglyToad.PdfPig.DocumentLayoutAnalysis/WordExtractor/NearestNeighbourWordExtractor.cs

@@ -51,34 +51,49 @@ public IEnumerable<Word> GetWords(IReadOnlyList<Letter> letters)
 
             if (options.GroupByOrientation)
             {
-                // axis aligned
-                List<Word> words = GetWords(
-                    letters.Where(l => l.TextOrientation == TextOrientation.Horizontal).ToList(),
-                    options.MaximumDistance, options.DistanceMeasureAA, options.FilterPivot,
-                    options.Filter, options.MaxDegreeOfParallelism);
-
-                words.AddRange(GetWords(
-                    letters.Where(l => l.TextOrientation == TextOrientation.Rotate270).ToList(),
-                    options.MaximumDistance, options.DistanceMeasureAA, options.FilterPivot,
-                    options.Filter, options.MaxDegreeOfParallelism));
+                var buckets = new List<Letter>[5];
+                for (int i = 0; i < buckets.Length; i++) buckets[i] = new List<Letter>();
 
-                words.AddRange(GetWords(
-                    letters.Where(l => l.TextOrientation == TextOrientation.Rotate180).ToList(),
-                    options.MaximumDistance, options.DistanceMeasureAA, options.FilterPivot,
-                    options.Filter, options.MaxDegreeOfParallelism));
-
-                words.AddRange(GetWords(
-                    letters.Where(l => l.TextOrientation == TextOrientation.Rotate90).ToList(),
-                    options.MaximumDistance, options.DistanceMeasureAA, options.FilterPivot,
-                    options.Filter, options.MaxDegreeOfParallelism));
+                foreach (var l in letters)
+                {
+                    switch (l.TextOrientation)
+                    {
+                        case TextOrientation.Horizontal: buckets[0].Add(l); break;
+                        case TextOrientation.Rotate270: buckets[1].Add(l); break;
+                        case TextOrientation.Rotate180: buckets[2].Add(l); break;
+                        case TextOrientation.Rotate90: buckets[3].Add(l); break;
+                        default: buckets[4].Add(l); break;
+                    }
+                }
 
-                // not axis aligned
-                words.AddRange(GetWords(
-                    letters.Where(l => l.TextOrientation == TextOrientation.Other).ToList(),
-                    options.MaximumDistance, options.DistanceMeasure, options.FilterPivot,
-                    options.Filter, options.MaxDegreeOfParallelism));
+                // Use a thread-safe collection to avoid lock contention.
+                var results = new List<Word>(letters.Count); // Pre-allocate for performance
 
-                return words;
+                // Limit parallelism to avoid oversubscription.
+                var parallelOptions = new System.Threading.Tasks.ParallelOptions
+                {
+                    MaxDegreeOfParallelism = options.MaxDegreeOfParallelism > 0 ? options.MaxDegreeOfParallelism : Environment.ProcessorCount
+                };
+
+                // Use partitioner for better load balancing and avoid ConcurrentBag overhead
+                System.Threading.Tasks.Parallel.ForEach(
+                    System.Collections.Concurrent.Partitioner.Create(0, buckets.Length),
+                    parallelOptions,
+                    range =>
+                    {
+                        for (int i = range.Item1; i < range.Item2; i++)
+                        {
+                            if (buckets[i].Count == 0) continue;
+                            var measure = (i == 4) ? options.DistanceMeasure : options.DistanceMeasureAA;
+                            var words = GetWords(buckets[i], options.MaximumDistance, measure, options.FilterPivot, options.Filter, options.MaxDegreeOfParallelism);
+                            lock (results)
+                            {
+                                results.AddRange(words);
+                            }
+                        }
+                    });
+                results.TrimExcess();
+                return results;
             }
             else
             {

src/UglyToad.PdfPig.Fonts/UglyToad.PdfPig.Fonts.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0;net9.0</TargetFrameworks>
     <LangVersion>12</LangVersion>
     <Version>0.1.12-alpha001</Version>
     <IsTestProject>False</IsTestProject>

src/UglyToad.PdfPig.Tests/UglyToad.PdfPig.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net471;net8.0</TargetFrameworks>
+    <TargetFrameworks>net471;net8.0;net9.0</TargetFrameworks>
     <IsTestProject>true</IsTestProject>
     <IsPackable>false</IsPackable>
     <DebugType>full</DebugType>

src/UglyToad.PdfPig.Tokenization/UglyToad.PdfPig.Tokenization.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0;net9.0</TargetFrameworks>
     <LangVersion>12</LangVersion>
     <Version>0.1.12-alpha001</Version>
     <IsTestProject>False</IsTestProject>

src/UglyToad.PdfPig.Tokens/UglyToad.PdfPig.Tokens.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0;net9.0</TargetFrameworks>
     <LangVersion>12</LangVersion>
     <Version>0.1.12-alpha001</Version>
     <IsTestProject>False</IsTestProject>

src/UglyToad.PdfPig/UglyToad.PdfPig.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net471;net6.0;net8.0;net9.0</TargetFrameworks>
     <LangVersion>12</LangVersion>
     <Version>0.1.12-alpha001</Version>
     <IsTestProject>False</IsTestProject>