Add error checking to ForCollapse

DotMP-Tests/ParallelTests.cs

@@ -1451,6 +1451,18 @@ public void Absent_params_shouldnt_except()
             Assert.Null(exception);
         }
 
+        /// <summary>
+        /// Verifies that for loops which overflow internal indices should throw an exception.
+        /// </summary>
+        [Fact]
+        public void Overflow_for_should_except()
+        {
+            Assert.Throws<DotMP.Exceptions.TooManyIterationsException>(() =>
+            {
+                DotMP.Parallel.ParallelForCollapse((0, 256), (0, 256), (0, 256), (0, 256), (i, j, k, l) => { });
+            });
+        }
+
         /// <summary>
         /// Verifies that invalid parameters throw exceptions.
         /// </summary>
@@ -1467,6 +1479,16 @@ public void Invalid_params_should_except()
                 DotMP.Parallel.ParallelFor(-1, 10, i => { });
             });
 
+            Assert.Throws<DotMP.Exceptions.InvalidArgumentsException>(() =>
+            {
+                DotMP.Parallel.ParallelForCollapse((10, 20), (-1, 10), (i, j) => { });
+            });
+
+            Assert.Throws<DotMP.Exceptions.InvalidArgumentsException>(() =>
+            {
+                DotMP.Parallel.ParallelForCollapse((10, 5), (0, 20), (i, j) => { });
+            });
+
             Assert.Throws<DotMP.Exceptions.InvalidArgumentsException>(() =>
             {
                 DotMP.Parallel.ParallelFor(10, -5, i => { });

DotMP/Wrappers.cs → DotMP/Chunk.cs

@@ -5,18 +5,18 @@
  * This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser
  * General Public License as published by the Free Software Foundation; either version 2.1 of the License, or
  * (at your option) any later version.
-
+ *
  * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
  * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  * License for more details.
-
+ *
  * You should have received a copy of the GNU Lesser General Public License along with this library; if not,
  * write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 using System;
 using System.Linq;
-using System.Runtime.CompilerServices;
+using DotMP.Exceptions;
 
 /* jscpd:ignore-start */
 namespace DotMP
@@ -179,7 +179,41 @@ private enum ActionSelector
         /// <summary>
         /// Represents the ranges of collapsed loops for future unflattening.
         /// </summary>
-        private ValueTuple<int, int>[] ranges;
+        private ValueTuple<int, int>[] ranges_prv;
+
+        /// <summary>
+        /// Represents the ranges of collapsed loops for unflattening, ensuring that loops do not have too many iterations.
+        /// </summary>
+        private ValueTuple<int, int>[] ranges
+        {
+            get => ranges_prv;
+            set
+            {
+                int total_iters = 1;
+
+                try
+                {
+                    foreach ((int start, int end) in value)
+                    {
+                        if (end < start)
+                            throw new InvalidArgumentsException(string.Format("Start of loop ({0}) must be less than end of loop ({1}).", start, end));
+
+                        if (start < 0 || end < 0)
+                            throw new InvalidArgumentsException(string.Format("Start ({0}) and end ({1}) of loop must both be positive integers.", start, end));
+
+                        total_iters = checked(total_iters * (end - start));
+                    }
+                }
+                catch (OverflowException)
+                {
+                    throw new TooManyIterationsException(string.Format("Parallel-for loop has too many iterations (exceeds {0}).", int.MaxValue));
+                }
+                finally
+                {
+                    ranges_prv = value;
+                }
+            }
+        }
 
         /// <summary>
         /// Array representing the starting indices.
@@ -420,7 +454,6 @@ private void ComputeIndicesN(int curr_iter, int[] indices)
 
         /// <summary>
         /// Executes a chunk using the action selected by ForAction.selector
-        /// TODO: Optimize this whole function.
         /// </summary>
         /// <param name="curr_iter">A reference to the current iteration.</param>
         /// <param name="start">The start of the chunk, inclusive.</param>

DotMP/Exceptions.cs

@@ -65,4 +65,16 @@ public class InvalidArgumentsException : Exception
         /// <param name="msg">The message to associate with the exception.</param>
         public InvalidArgumentsException(string msg) : base(msg) { }
     }
+
+    /// <summary>
+    /// Exception thrown if a for loop has too many iterations and would cause the schedulers to fail.
+    /// </summary>
+    public class TooManyIterationsException : Exception
+    {
+        /// <summary>
+        /// Constructor with a message.
+        /// </summary>
+        /// <param name="msg">The message to associate with the exception.</param>
+        public TooManyIterationsException(string msg) : base(msg) { }
+    }
 }

DotMP/Parallel.cs

@@ -204,6 +204,7 @@ public static void For(int start, int end, Action<int> action, IScheduler schedu
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception> 
         public static void ForCollapse((int, int) firstRange, (int, int) secondRange, Action<int, int> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<object> forAction = new ForAction<object>(action, new (int, int)[] { firstRange, secondRange });
@@ -231,6 +232,7 @@ public static void ForCollapse((int, int) firstRange, (int, int) secondRange, Ac
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception>
         public static void ForCollapse((int, int) firstRange, (int, int) secondRange, (int, int) thirdRange, Action<int, int, int> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<object> forAction = new ForAction<object>(action, new (int, int)[] { firstRange, secondRange, thirdRange });
@@ -260,6 +262,7 @@ public static void ForCollapse((int, int) firstRange, (int, int) secondRange, (i
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception>
         public static void ForCollapse((int, int) firstRange, (int, int) secondRange, (int, int) thirdRange, (int, int) fourthRange, Action<int, int, int, int> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<object> forAction = new ForAction<object>(action, new (int, int)[] { firstRange, secondRange, thirdRange, fourthRange });
@@ -287,6 +290,7 @@ public static void ForCollapse((int, int) firstRange, (int, int) secondRange, (i
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception>
         public static void ForCollapse((int, int)[] ranges, Action<int[]> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<object> forAction = new ForAction<object>(action, ranges);
@@ -394,6 +398,7 @@ public static void ForReduction<T>(int start, int end, Operations op, ref T redu
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception>
         public static void ForReductionCollapse<T>((int, int) firstRange, (int, int) secondRange, Operations op, ref T reduce_to, ActionRef2<T> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<T> forAction = new ForAction<T>(action, new (int, int)[] { firstRange, secondRange });
@@ -426,6 +431,7 @@ public static void ForReductionCollapse<T>((int, int) firstRange, (int, int) sec
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception>
         public static void ForReductionCollapse<T>((int, int) firstRange, (int, int) secondRange, (int, int) thirdRange, Operations op, ref T reduce_to, ActionRef3<T> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<T> forAction = new ForAction<T>(action, new (int, int)[] { firstRange, secondRange, thirdRange });
@@ -460,6 +466,7 @@ public static void ForReductionCollapse<T>((int, int) firstRange, (int, int) sec
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception>
         public static void ForReductionCollapse<T>((int, int) firstRange, (int, int) secondRange, (int, int) thirdRange, (int, int) fourthRange, Operations op, ref T reduce_to, ActionRef4<T> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<T> forAction = new ForAction<T>(action, new (int, int)[] { firstRange, secondRange, thirdRange, fourthRange });
@@ -492,6 +499,7 @@ public static void ForReductionCollapse<T>((int, int) firstRange, (int, int) sec
         /// <exception cref="NotInParallelRegionException">Thrown when not in a parallel region.</exception>
         /// <exception cref="CannotPerformNestedWorksharingException">Thrown when nested inside another worksharing region.</exception>
         /// <exception cref="InvalidArgumentsException">Thrown if any provided arguments are invalid.</exception>
+        /// <exception cref="TooManyIterationsException">Thrown if there are too many iterations to handle.</exception>
         public static void ForReductionCollapse<T>((int, int)[] ranges, Operations op, ref T reduce_to, ActionRefN<T> action, IScheduler schedule = null, uint? chunk_size = null)
         {
             ForAction<T> forAction = new ForAction<T>(action, ranges);