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Faster Chips Are Leaving Programmers in Their Dust
mlimber writes "The New York Times is running a story about multicore computing and the efforts of Microsoft et al. to try to switch to the new paradigm: "The challenges [of parallel programming] have not dented the enthusiasm for the potential of the new parallel chips at Microsoft, where executives are betting that the arrival of manycore chips — processors with more than eight cores, possible as soon as 2010 — will transform the world of personal computing.... Engineers and computer scientists acknowledge that despite advances in recent decades, the computer industry is still lagging in its ability to write parallel programs." It mirrors what C++ guru and now Microsoft architect Herb Sutter has been saying in articles such as his "The Free Lunch Is Over: A Fundamental Turn Toward Concurrency in Software." Sutter is part of the C++ standards committee that is working hard to make multithreading standard in C++."
....it wants it's article back.
Seriously - any developer writing modern desktop or server applications that doesn't know how to do multi-threaded programming effectively deserves to be on EI anyway. It is not that difficult.
just start a multithread process: 1 core for the program itself, the remaining 7 for the bugs...
II hhaavvee aann XX22 pprrocceessssoor? Ii ccaann ggooeess TTWWIICCEE aass ffaasstt nnooww?
"...Well, there's egg and bacon; egg sausage and bacon; egg and spam; egg bacon and spam; egg bacon sausage and spam..."
Some algorithms are inherently not amenable to parallelization. If you have eight cores instead of one, then the performance boost you can get can be anywhere from eight times faster to none at all.
So far, multiple cores have boosted performance mostly because the typical user has multiple applications running at a time. But as the number of cores increases, the beneficial effects diminish dramatically.
In addition, most applications these days are not CPU bound. Having eight cores doesn't help you much when three are waiting on socket calls, four are waiting on disk access calls and the last is waiting for the graphics card.
The cake is a pie
"processors with more than eight cores, possible as soon as 2010 -- will transform the world of personal computing"
Exactly what areas of "personal computing" are requiring this horsepower? The only two that come to mind are games and encoding video. The video encoding part is already covered - that scales nicely to multiple threads, and even free encoders will use the extra cores to their full potential. That leaves gaming, which is basically proprietary. The game engine must be designed so that AI, physics, and other CPU-bound algorithms can be executed in parallel. This has already been addressed.
So this begs the question, exactly how will average consumer benefit from an OS and software that can make optimum use of multiple cores, when the performance issues users complain about are not even CPU-bound in the first place?
Dan East
Better known as 318230.
The only significant thing that managed languages make easier with regard to multithreading other than a more intuitive API is garbage collection so that you don't have to worry about using reference counting when passing pointers between multiple threads.
All of the same challenges that exist in C/C++ such as deadly embrace and dining philosophers still exist in managed languages and require the developer to be trained in multi-threaded programming.
Some things can be more difficult to implement like semaphores. You also have to be careful about what asynchronous methods and events you invoke because those get queued up on the thread pool and it has a max count.
I would say managed languages are "easier" to use but to be used effectively you still have to understand the fundamental concepts of multithreaded programming and what's going on underneath the hood of your runtime environment.
We'll make great pets
Full disclosure: I am a Qt Developer (user) I do not work for TrollTech
The new Qt4.4 (due 1Q2008) has QtConcurrent, a set of classes that make multi-core processing trivial.
From the docs:
The QtConcurrent namespace provides high-level APIs that make it possible to write multi-threaded programs without using low-level threading primitives such as mutexes, read-write locks, wait conditions, or semaphores. Programs written with QtConcurrent automaticallly adjust the number of threads used according to the number of processor cores available. This means that applications written today will continue to scale when deployed on multi-core systems in the future.
QtConcurrent includes functional programming style APIs for parallel list prosessing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications:
* QtConcurrent::map() applies a function to every item in a container, modifying the items in-place.
* QtConcurrent::mapped() is like map(), except that it returns a new container with the modifications.
* QtConcurrent::mappedReduced() is like mapped(), except that the modified results are reduced or folded into a single result.
* QtConcurrent::filter() removes all items from a container based on the result of a filter function.
* QtConcurrent::filtered() is like filter(), except that it returns a new container with the filtered results.
* QtConcurrent::filteredReduced() is like filtered(), except that the filtered results are reduced or folded into a single result.
* QtConcurrent::run() runs a function in another thread.
* QFuture represents the result of an asynchronous computation.
* QFutureIterator allows iterating through results available via QFuture.
* QFutureWatcher allows monitoring a QFuture using signals-and-slots.
* QFutureSynchronizer is a convenience class that automatically synchronizes several QFutures.
* QRunnable is an abstract class representing a runnable object.
* QThreadPool manages a pool of threads that run QRunnable objects.
This makes multi-core programming almost a no-brainer.
Slashdot's rate-of-post filter: Preventing you from posting too many great ideas at once.
processors with more than eight cores, possible as soon as 2010 -- will transform the world of personal computing....
Translation:
Code will get even more inefficient / bloated and require faster hardware to do the same thing you are doing now. While I'm all for better / faster computer hardware, most if not all Jane and Joe Sixpack users never need Super Computer power to surf the net, read e-mail and watch videos.
"I bow to no man" - Riddick
A guy who's on the C++ standards committee AND works for Microsoft.
Actually, according to the latest Dr Dobbs, Herb is the *chair* of the ISO C++ Standards committee. (He had an article on lock hierarchies being used to avoid deadlock)
He's really going to know what he's talking about, then.
As chair of the committee, I'd say there's a pretty fair chance that he *does*.
I really love people who bash things just because Microsoft is involved. Contrary to what seems to be a popular belief here, they have some incredibly intelligent people who are very good at what they do there.
Everything I need to know I learned by killing smart people and eating their brains.
This is very, very wrong. Data-set partitioning is certainly one way of achieving parallelism in programming, but it is hardly the only way- nor is it applicable to all domains, as many problems have solutions with too many inter-cell data dependencies. In addition, threads provide a wealth of benefits to application developers by allowing multiple unrelated tasks to be performed simultaneously.
There is, and will always be, overhead associated with parallelization. It may sound great to say "oh, we can farm out parts of this data set to other cores!", but that requires a lot of start-up and tear-down synchronization. It's not at all uncommon for overall performance to be improved by doing something *unrelated* at the same time, requiring less synchronization overhead.
Are threads perfect for everything? No. But calling them the second worse thing to happen to computing is, as best, disingenuous.
The ringing of the division bell has begun... -PF
You may want to switch of the rapid fire-mode for your "."-key.