Why one loop is performing better than other memory wise as well as performance wise?
- by Mohit
I have following two loops in C#, and I am running these loops for a collection with 10,000 records being downloaded with paging using "yield return"
First
foreach(var k in collection) {
repo.Save(k);
}
Second
var collectionEnum = collection.GetEnumerator();
while (collectionEnum.MoveNext()) {
var k = collectionEnum.Current;
repo.Save(k);
k = null;
}
Seems like that the second loop consumes less memory and it faster than the first loop. Memory I understand may be because of k being set to null(Even though I am not sure). But how come it is faster than for each.
Following is the actual code
[Test]
public void BechmarkForEach_Test() {
bool isFirstTimeSync = true;
Func<Contact, bool> afterProcessing = contactItem => {
return true;
};
var contactService = CreateSerivce("/administrator/components/com_civicrm");
var contactRepo = new ContactRepository(new Mock<ILogger>().Object);
contactRepo.Drop();
contactRepo = new ContactRepository(new Mock<ILogger>().Object);
Profile("For Each Profiling",1,()=>{
var localenumertaor=contactService.Download();
foreach (var item in localenumertaor) {
if (isFirstTimeSync)
item.StateFlag = 1;
item.ClientTimeStamp = DateTime.UtcNow;
if (item.StateFlag == 1)
contactRepo.Insert(item);
else
contactRepo.Update(item);
afterProcessing(item);
}
contactRepo.DeleteAll();
});
}
[Test]
public void BechmarkWhile_Test() {
bool isFirstTimeSync = true;
Func<Contact, bool> afterProcessing = contactItem => {
return true;
};
var contactService = CreateSerivce("/administrator/components/com_civicrm");
var contactRepo = new ContactRepository(new Mock<ILogger>().Object);
contactRepo.Drop();
contactRepo = new ContactRepository(new Mock<ILogger>().Object);
var itemsCollection = contactService.Download().GetEnumerator();
Profile("While Profiling", 1, () =>
{
while (itemsCollection.MoveNext()) {
var item = itemsCollection.Current;
//if First time sync then ignore and overwrite the stateflag
if (isFirstTimeSync)
item.StateFlag = 1;
item.ClientTimeStamp = DateTime.UtcNow;
if (item.StateFlag == 1)
contactRepo.Insert(item);
else
contactRepo.Update(item);
afterProcessing(item);
item = null;
}
contactRepo.DeleteAll();
});
}
static void Profile(string description, int iterations, Action func) {
// clean up
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();
// warm up
func();
var watch = Stopwatch.StartNew();
for (int i = 0; i < iterations; i++) {
func();
}
watch.Stop();
Console.Write(description);
Console.WriteLine(" Time Elapsed {0} ms", watch.ElapsedMilliseconds);
}
I m using the micro bench marking, from a stackoverflow question itself benchmarking-small-code
The time taken is
For Each Profiling Time Elapsed 5249 ms
While Profiling Time Elapsed 116 ms
