How to sum up an array of integers in C

Question

Is there a better shorter way than iterating over the array   int   arr   new int     1  2  3    int sum   0  for  int i   0  i  lt  arr Length  i          sum    arr i         clarification   Better primary means cleaner code but hints on performance improvement are also welcome   Like already mentioned  splitting large arrays      It s not like I was looking for killer performance improvement - I just wondered if this very kind of syntactic sugar wasn t already available   There s String Join - what the heck about int

User · Answer

Using foreach would be shorter code  but probably do exactly the same steps at runtime after JIT optimization recognizes the comparison to Length in the for-loop controlling expression

User · Answer

In one of my apps I used    public class ClassBlock       public int   p      public int Sum               get   int s   0   Array ForEach p  delegate  int i    s    i      return s

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For extremely large arrays it may pay off to perform the calculation using more than one processors cores of the machine  long sum   0  var options   new ParallelOptions         MaxDegreeOfParallelism   Environment ProcessorCount    Parallel ForEach Partitioner Create 0  arr Length   options  range   gt        long localSum   0      for  int i   range Item1  i  lt  range Item2  i                  localSum    arr i             Interlocked Add ref sum  localSum

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If you don t prefer LINQ  it is better to use foreach loop to avoid out of index   int   arr   new int     1  2  3    int sum   0  foreach  var item in arr       sum    item

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With LINQ   arr Sum

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Yes there is  With  NET 3 5   int sum   arr Sum    Console WriteLine sum     If you re not using  NET 3 5 you could do this   int sum   0  Array ForEach arr  delegate int i    sum    i      Console WriteLine sum

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Try this code   using System   namespace Array       class Program               static void Main                         int   number   new int    5  5  6  7                int sum   0              for  int i   0  i  lt number Length  i                                  sum    number i                             Console WriteLine sum                        The result is      23

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Provided that you can use  NET 3 5  or newer  and LINQ  try   int sum   arr Sum

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One problem with the for loop solutions above is that for the following input array with all positive values  the sum result is negative   int   arr   new int     Int32 MaxValue  1    int sum   0  for  int i   0  i  lt  arr Length  i          sum    arr i     Console WriteLine sum     The sum is -2147483648  as the positive result is too big for the int data type and overflows into a negative value   For the same input array the arr Sum   suggestions cause an overflow exception to be thrown   A more robust solution is to use a larger data type  such as a  long  in this case  for the  sum  as follows   int   arr   new int     Int32 MaxValue  1    long sum   0  for  int i   0  i  lt  arr Length  i          sum    arr i       The same improvement works for summation of other integer data types  such as short  and sbyte  For arrays of unsigned integer data types such as uint  ushort and byte  using an unsigned long  ulong  for the sum avoids the overflow exception   The for loop solution is also many times faster than Linq  Sum    To run even faster  HPCsharp nuget package implements all of these  Sum   versions as well as SIMD SSE versions and multi-core parallel ones  for many times faster performance

User · Answer

It depends on how you define better  If you want the code to look cleaner  you can use  Sum   as mentioned in other answers  If you want the operation to run quickly and you have a large array  you can make it parallel by breaking it into sub sums and then sum the results

User · Answer

An alternative also it to use the Aggregate   extension method   var sum   arr Aggregate  temp  x    gt  temp x

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An improvement on Theodor Zoulias s nice multi-core Parallel ForEach implementation       public static ulong SumToUlongPar this uint   arrayToSum  int startIndex  int length  int degreeOfParallelism   0                var concurrentSums   new ConcurrentBag lt ulong gt              int maxDegreeOfPar   degreeOfParallelism  lt   0   Environment ProcessorCount   degreeOfParallelism          var options   new ParallelOptions     MaxDegreeOfParallelism   maxDegreeOfPar             Parallel ForEach Partitioner Create startIndex  startIndex   length   options  range   gt                        ulong localSum   0              for  int i   range Item1  i  lt  range Item2  i                    localSum    arrayToSum i               concurrentSums Add localSum                        ulong sum   0          var sumsArray   concurrentSums ToArray            for  int i   0  i  lt  sumsArray Length  i                sum    sumsArray i            return sum          which works for unsigned integer data types  since C  only support Interlocked Add   for int and long  The above implementation can also be easily modified to support other integer and floating-point data types to do summation in parallel using multiple cores of the CPU  It is used in the HPCsharp nuget package

[c#] How to sum up an array of integers in C#

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