diff --git a/SearchBox-CLI/Program.cs b/SearchBox-CLI/Program.cs
index 64d3832..7e2db00 100644
--- a/SearchBox-CLI/Program.cs
+++ b/SearchBox-CLI/Program.cs
@@ -7,6 +7,8 @@ using Newtonsoft.Json;
 using LibSearchBox;
 using System.Text.RegularExpressions;
 using Newtonsoft.Json.Serialization;
+using System.Threading.Tasks;
+using SBRL.Utilities;
 
 namespace SearchBoxCLI
 {
@@ -156,22 +158,23 @@ namespace SearchBoxCLI
 			if (!Batch)
 				searchBox.AddDocument(Name, Tags, Source.ReadToEnd());
 			else {
-				string nextLine = "";
-				while ((nextLine = Source.ReadLine()) != null) {
-					string[] parts = nextLine.Split('|');
-					if (parts[0].Trim().Length == 0)
-						continue;
-					try {
+				try
+				{
+					Parallel.ForEach(LineIterator.GetLines(Source), (string nextLine) => {
+						string[] parts = nextLine.Split('|');
+						if (parts[0].Trim().Length == 0)
+							return;
+						
 						searchBox.AddDocument(
 							parts[1].Trim(),
 							Regex.Split(parts[2], @",\s*"),
 							File.ReadAllText(parts[0].Trim())
 						);
 						Console.Error.WriteLine($"[Searchbox] [add] {parts[0].Trim()}");
-					} catch (FileNotFoundException) {
-						Console.Error.WriteLine($"Error: Can't find file {parts[2].Trim()}.");
-						return 1;
-					}
+					});
+				} catch (FileNotFoundException error) {
+					Console.Error.WriteLine(error.Message);
+					return 1;
 				}
 			}
 
diff --git a/SearchBox-CLI/SearchBox-CLI.csproj b/SearchBox-CLI/SearchBox-CLI.csproj
index 9560f3a..110dd92 100644
--- a/SearchBox-CLI/SearchBox-CLI.csproj
+++ b/SearchBox-CLI/SearchBox-CLI.csproj
@@ -40,6 +40,7 @@
   <ItemGroup>
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="Utilities\LineIterator.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\SearchBox\SearchBox.csproj">
@@ -50,5 +51,8 @@
   <ItemGroup>
     <None Include="packages.config" />
   </ItemGroup>
+  <ItemGroup>
+    <Folder Include="Utilities\" />
+  </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>
\ No newline at end of file
diff --git a/SearchBox-CLI/Utilities/LineIterator.cs b/SearchBox-CLI/Utilities/LineIterator.cs
new file mode 100644
index 0000000..5d2cc1a
--- /dev/null
+++ b/SearchBox-CLI/Utilities/LineIterator.cs
@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace SBRL.Utilities
+{
+	static class LineIterator {
+		
+		public static IEnumerable<string> GetLines(TextReader source)
+		{
+			string nextLine;
+			while ((nextLine = source.ReadLine()) != null) {
+				yield return nextLine;
+			}
+		}
+
+		public static IEnumerable<string> GetLines(string source)
+		{
+			source = source.Replace("\r\n", "\n");
+			int curPosition = 0, nextIndex;
+			while (true)
+			{
+				nextIndex = source.IndexOf("\n", curPosition);
+				if (nextIndex == -1)
+					break;
+
+				yield return source.Substring(curPosition, nextIndex - curPosition);
+
+				curPosition = nextIndex + 1;
+			}
+		}
+
+	}
+}
\ No newline at end of file
diff --git a/SearchBox/IdMap.cs b/SearchBox/IdMap.cs
index 05b572a..3403ee6 100644
--- a/SearchBox/IdMap.cs
+++ b/SearchBox/IdMap.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using System.Threading;
 using Newtonsoft.Json;
 using Stackoverflow.Utilities;
 
@@ -41,6 +42,12 @@ namespace LibSearchBox
 			nextId = map.Max((pair) => pair.First) + 1;
 		}
 
+		private int generateNewId()
+		{
+			int incremented = Interlocked.Increment(ref nextId);
+			return incremented - 1; // Only the incrementing itself has to be atomic
+		}
+
 
 		public int GetId(string pageName)
 		{
@@ -49,7 +56,7 @@ namespace LibSearchBox
 
 			int result;
 			if (!map.TryGetBySecond(pageName, out result)) {
-				map.Add(result = nextId++, pageName);
+				map.Add(result = generateNewId(), pageName);
 			}
 			return result;
 		}
diff --git a/SearchBox/Utilities/BiDictionary.cs b/SearchBox/Utilities/BiDictionary.cs
index 42e4328..be67835 100644
--- a/SearchBox/Utilities/BiDictionary.cs
+++ b/SearchBox/Utilities/BiDictionary.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 
 namespace Stackoverflow.Utilities
@@ -26,9 +27,9 @@ namespace Stackoverflow.Utilities
 		public struct Enumerator : IEnumerator<Pair>, IEnumerator
 		{
 
-			public Enumerator(Dictionary<TFirst, TSecond>.Enumerator dictEnumerator)
+			public Enumerator(IEnumerable<KeyValuePair<TFirst, TSecond>> dictEnumerator)
 			{
-				_dictEnumerator = dictEnumerator;
+				_dictEnumerator = dictEnumerator.GetEnumerator();
 			}
 
 			public Pair Current {
@@ -61,7 +62,7 @@ namespace Stackoverflow.Utilities
 				throw new NotSupportedException();
 			}
 
-			private Dictionary<TFirst, TSecond>.Enumerator _dictEnumerator;
+			private IEnumerator<KeyValuePair<TFirst, TSecond>> _dictEnumerator;
 
 		}
 
@@ -78,8 +79,8 @@ namespace Stackoverflow.Utilities
 			if (_firstToSecond.ContainsKey(first) || _secondToFirst.ContainsKey(second))
 				throw new ArgumentException("Duplicate first or second");
 
-			_firstToSecond.Add(first, second);
-			_secondToFirst.Add(second, first);
+			_firstToSecond.TryAdd(first, second);
+			_secondToFirst.TryAdd(second, first);
 		}
 
 		/// <summary>
@@ -124,8 +125,8 @@ namespace Stackoverflow.Utilities
 			if (!_firstToSecond.TryGetValue(first, out second))
 				throw new ArgumentException("first");
 
-			_firstToSecond.Remove(first);
-			_secondToFirst.Remove(second);
+			_firstToSecond.TryRemove(first, out TSecond noop);
+			_secondToFirst.TryRemove(second, out TFirst noopAgain);
 		}
 
 		/// <summary>
@@ -139,8 +140,8 @@ namespace Stackoverflow.Utilities
 			if (!_secondToFirst.TryGetValue(second, out first))
 				throw new ArgumentException("second");
 
-			_secondToFirst.Remove(second);
-			_firstToSecond.Remove(first);
+			_secondToFirst.TryRemove(second, out TFirst noop);
+			_firstToSecond.TryRemove(first, out TSecond noopAgain);
 		}
 
 		#endregion
@@ -159,9 +160,9 @@ namespace Stackoverflow.Utilities
 			if (_firstToSecond.ContainsKey(first) || _secondToFirst.ContainsKey(second))
 				return false;
 
-			_firstToSecond.Add(first, second);
-			_secondToFirst.Add(second, first);
-			return true;
+			bool result = _firstToSecond.TryAdd(first, second);
+			result = _secondToFirst.TryAdd(second, first) || result;
+			return result;
 		}
 
 
@@ -200,9 +201,9 @@ namespace Stackoverflow.Utilities
 			if (!_firstToSecond.TryGetValue(first, out second))
 				return false;
 
-			_firstToSecond.Remove(first);
-			_secondToFirst.Remove(second);
-			return true;
+			bool result = _firstToSecond.TryRemove(first, out TSecond noop);
+			result = _secondToFirst.TryRemove(second, out TFirst noopAgain) || result;
+			return result;
 		}
 
 		/// <summary>
@@ -216,8 +217,8 @@ namespace Stackoverflow.Utilities
 			if (!_secondToFirst.TryGetValue(second, out first))
 				return false;
 
-			_secondToFirst.Remove(second);
-			_firstToSecond.Remove(first);
+			_secondToFirst.TryRemove(second, out TFirst noop);
+			_firstToSecond.TryRemove(first, out TSecond noopAgain);
 			return true;
 		}
 
@@ -243,7 +244,7 @@ namespace Stackoverflow.Utilities
 		public Enumerator GetEnumerator()
 		{
 			//enumerator.Reset(firstToSecond.GetEnumerator());
-			return new Enumerator(_firstToSecond.GetEnumerator());
+			return new Enumerator(_firstToSecond);
 		}
 
 		IEnumerator<Pair> IEnumerable<Pair>.GetEnumerator()
@@ -258,8 +259,8 @@ namespace Stackoverflow.Utilities
 
 
 
-		private Dictionary<TFirst, TSecond> _firstToSecond = new Dictionary<TFirst, TSecond>();
-		private Dictionary<TSecond, TFirst> _secondToFirst = new Dictionary<TSecond, TFirst>();
+		private ConcurrentDictionary<TFirst, TSecond> _firstToSecond = new ConcurrentDictionary<TFirst, TSecond>();
+		private ConcurrentDictionary<TSecond, TFirst> _secondToFirst = new ConcurrentDictionary<TSecond, TFirst>();
 
 	}
 }
\ No newline at end of file