CODEWITHSUNDEEP
c++windowsperformancememory-managementcpu
TimeCoder
TimeCoder

Reputation: 1477

Increasing C++ Program CPU Use

I have a program written in C++ that runs a number of for loops per second without using anything that would make it wait for any reason. It consistently uses 2-10% of the CPU. Is there any way to force it to use more of the CPU and do a greater number of calculations without making the program more complex? Additionally, I compile with C::B on a Windows computer. Essentially, I'm asking whether there is a way to make my program faster by increasing usage of CPU, and if so, how.

Upvotes: 5

Views: 9047

Answers (6)

Tom
Tom

Reputation: 5299

Some profilers give very nice indications of where bottlenecks in your code are. For example - the CodeAnalyst (for AMD chips only) has the instructions per cycle ratio. I'm sure intel profilers are similar.

As Billy O'Neal says though, if your runnning on an 8-core, being stuck on 10 percent of cpu is about right. If this is your problem then Windows msvc++ has a parallel mode (the parallel patterns library) for the standard algorithms. This can give parallelisation for free if have written your loops the c++ way (its still your responsibility to make sure your loops are thread safe). I've not used the msvc version but the gnu::__parallel_for_each etc work a treat.

Upvotes: 0

Billy ONeal
Billy ONeal

Reputation: 106530

That depends on why it's only using 10% of the CPU. If it's because you're using a multi-CPU machine and your program is using only one CPU, then no, you will have to introduce concurrency into your code to use that additional horsepower.

If it's being limited by something else (e.g. copying data to and from the disk), then you don't need to focus on CPU, you need to focus on whatever the bottleneck is. Most likely, the limiter will be reading from the disk, which you can improve by using better caching mechanisms.

Upvotes: 6

paxdiablo
paxdiablo

Reputation: 881093

Assuming your application has the power (PROCESS_SET_INFORMATION access right), you can use SetPriorityClass to bump up your priortiy (to the usual detriment of all other processes, of course).

You can go ABOVE_NORMAL_PRIORITY_CLASS (try this one first), HIGH_PRIORITY_CLASS (be very careful with this one) or REALTIME_PRIORITY_CLASS (I would strongly suggest that you probably shouldn't give this one a shot).

If you try the higher priorities and it's still clocking pretty low, then that's probably because you're not CPU-bound (such as if you're writing data to an output file). If that's the case, you'll probably have to find a way to make yourself CPU bound.

Just keep in mind that doing so may not be necessary (or even desirable). If you're running at a higher priority than other threads and you're still not sucking up a lot of CPU, it's probably because Windows has (most likely, rightfully) decided you don't need it.

Upvotes: 5

ssube
ssube

Reputation: 48247

It's really not the program's right or responsibility to demand additional resources from the system. That's the OS' job, as resource scheduler.

If it is necessary to use more CPU time than the OS sees fit, you should request that from the OS using the platform-dependent API. In this case, that seems to be something along the lines of SetPriorityClass or SetThreadPriority.

Upvotes: 5

prosseek
prosseek

Reputation: 190659

If you use C++, consider using Intel Threading Building Block. You can find some examples here.

Upvotes: 0

Alok Save
Alok Save

Reputation: 206498

Creating a thread & giving higher priority to the thread might be one way.

Upvotes: 0

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