What is the best way way to track progress in the following
long total = Products.LongCount();
long current = 0;
double Progress = 0.0;
Parallel.ForEach(Products, product =>
{
try
{
var price = GetPrice(SystemAccount, product);
SavePrice(product,price);
}
finally
{
Interlocked.Decrement(ref this.current);
}});
I want to update the progress variable from 0.0 to 1.0 (current/total) but i don't want to use anything that would have an adverse effect on the parallelism.
You don't have to do anything special, Parallel. Foreach() will wait until all its branched tasks are complete. From the calling thread you can treat it as a single synchronous statement and for instance wrap it inside a try/catch.
No, it doesn't block and returns control immediately. The items to run in parallel are done on background threads.
ForEach is like the foreach loop in C#, except the foreach loop runs on a single thread and processing take place sequentially, while the Parallel. ForEach loop runs on multiple threads and the processing takes place in a parallel manner.
Jon's solution is good, if you need simple synchronization like this, your first attempt should almost always use lock
. But if you measure that the locking slows things too much, you should think about using something like Interlocked
.
In this case, I would use Interlocked.Increment
to increment the current count, and change Progress
into a property:
private long total;
private long current;
public double Progress
{
get
{
if (total == 0)
return 0;
return (double)current / total;
}
}
…
this.total = Products.LongCount();
this.current = 0;
Parallel.ForEach(Products, product =>
{
try
{
var price = GetPrice(SystemAccount, product);
SavePrice(product, price);
}
finally
{
Interlocked.Increment(ref this.current);
}
});
Also, you might want to consider what to do with exceptions, I'm not sure that iterations that ended with an exception should be counted as done.
Since you are just doing a few quick calculations, ensure atomicity by locking on an appropriate object:
long total = Products.LongCount();
long current = 0;
double Progress = 0.0;
var lockTarget = new object();
Parallel.ForEach(Products, product =>
{
try
{
var price = GetPrice(SystemAccount, product);
SavePrice(product,price);
}
finally
{
lock (lockTarget) {
Progress = ++this.current / total;
}
}});
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With