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AnswerRe: C# How to speed up for loop with large data iteration Pin
Richard MacCutchan29-Apr-21 3:07
mveRichard MacCutchan29-Apr-21 3:07 
AnswerRe: C# How to speed up for loop with large data iteration Pin
OriginalGriff29-Apr-21 4:16
mveOriginalGriff29-Apr-21 4:16 
Richard is right:
Quote:
Which lines are taking the longest to execute?

And so is Richard:
Quote:
you need to understand that processing just over 2.5 million items will take some time.


The first part of any speed improvement exercise is to find out what you have: and that means timing your code to find out what takes a "long time" and what is "quick" - there is no point in trying to squeeze improvements out of fast code because that will make marginal difference; the slow code is teh bit that needs speeding up.
So start with the Stopwatch Class (System.Diagnostics) | Microsoft Docs[^] and start finding out where that code runs quick, and where it runs slow.
We can't do that for you: we don't have any access to your data, and it's likely to be very relevant to any speed analysis.

When you have that, you also have a metric for much improvement you are making as you go.

It's possible that you might be able to multithread it, to spread the load out over the whole processor - but that's not as simple as it may sound: although thinks like Parallel.Foreach exist, using threading blindly is as likely to slow down your whole computer as speed up processing, particularly when you start dealing with 2,000,000 items each of which probably don't take much time so the additional thread setup / processing overhead starts to overweigh the actual task.
You may get some good "throughput" improvements by splitting the for loop into a small number N of threads, each of which does 1/N th of the total task. But remember: List and DataTable are not considered thread safe, so you'll probably need to think very carefully before you start coding that if you don't want really hard to spot and track down data bugs.
As a general rule, I wouldn't recommend trying to use more threads than you have cores ...
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AnswerRe: C# How to speed up for loop with large data iteration Pin
Gerry Schmitz29-Apr-21 9:03
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GeneralRe: C# How to speed up for loop with large data iteration Pin
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GeneralRe: C# How to speed up for loop with large data iteration Pin
Gerry Schmitz30-Apr-21 8:22
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GeneralRe: C# How to speed up for loop with large data iteration Pin
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