Multi threading in C#

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i have 19 loops in amy app

and 18 levels of nesting. and every loop itrates 100 times;

it aproximately does 100 raised to the power 19.

it takes a very long time to perform such operation.
can we make it faster by doing simple multi-threading !! :confused:

Thanks & Regards
Nakul Kundra
9999788629

Posted 12-Oct-10 5:36am

nakulkundra

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LittleYellowBird 12-Oct-10 11:41am

Hi, If I understand you correctly it does the loop 19 times and that is repeated 100 times. Nesting does not come into it. So that is only 1900 times not 100 to the power of 19? 100 to the power of 19 is a very big number! Perhaps you need to check your figures it might not be repeating as often as you think. :)

nakulkundra 12-Oct-10 13:08pm

no its 100 to the power of 19

10000000000000000000000000000000000000
much and it takes 6hrs to do so

shakil0304003 12-Oct-10 14:22pm

I think it is impossible to execute 10000000000000000000000000000000000000
loop in 6 hours. you can try by a simple code
for(long i=0;i<10000000000;i++)
for(long j=0;j<10000000000;j++)
{}
this codes complexity is less then your complexity & this code can not execute with in 6 hours, i think ;)

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shakil0304003 · Answer 1 · 2010-10-12T08:15:00

Solution 4

18 levels of nesting. and every loop itrates 100 times; it can not be solved by multi-threading. It is also hard to solve in parallel processors because every loop dependent on another loop. In parallel processing you can process independent process parallel but dependent process can not execute parallel. And now your complexity is 100^18 = 10^19, if you will able to do it in parallel processing then to execute it in one sec you have to need 1000000000000 parallel processor. If you want to execute it in one month then you have to need 385802 parallel processors. So, i think you have to minimize the loops, there is no other option ;)

Posted 12-Oct-10 8:15am

shakil0304003

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Keith Barrow 12-Oct-10 17:06pm

My vote of 1:
"18 levels of nesting. and every loop itrates 100 times; it can not be solved by multi-threading."
Not true. He doesn't say what is being processed, if it is an "embarrassingly parallel" process, it can be. If he has 4 cores, then he will divide his process time by ~ 1/4. He *should* sort out the nesting, but parallelism can (but not necessarily will) help.

shakil0304003 12-Oct-10 23:33pm

likely 100000000 operations can be work in 1 sec. he needs 10^19 operation, so it should be need 100000000000 sec, but he said that it takes 6 hours, i think by some reason, his program crashed after 6 hour. I think it may be for his memory, he stored all the data. now, by your say, if i divide the process time 1/4 then it will take 25000000000 sec, which also not physible.

Keith Barrow · Answer 2 · 2010-10-12T07:30:00

Firstly, there is a good chance that you are doing something wrong if you have such deep nesting. Have a look at your algorithm to see if there is anything you can do to factor these out first.

Then you should look at the followings MS PDF document. It outlines solutions to various parallel problems, using the new additions in .net 4.0 to support the same.

http://download.microsoft.com/download/3/4/D/34D13993-2132-4E04-AE48-53D3150057BD/Patterns_of_Parallel_Programming_CSharp.pd[^]

#realJSOP · Answer 3 · 2010-10-12T08:02:00

Solution 3

Here's one approach.

Start a thread that processes from each end of the arrays, and two more that start at the center of the arrays. Eventaully each pair od threads should intersect. It would take 1/4 of the time to process the arrays.

Posted 12-Oct-10 8:02am

#realJSOP

Abhinav S · Answer 4 · 2010-10-12T05:44:00

Solution 1

You can actually look at running loops on parallel processors (if this is supported in the framework you use) - see http://blog.robvolk.com/2009/06/parallel-foreach-loop-in-c-35.html[^].

Posted 12-Oct-10 5:44am

Abhinav S

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nakulkundra 12-Oct-10 13:09pm

no i dnt have parallel processors

Multi threading in C#

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