From http://herbsutter.spaces.live.com :
For those of you who may be interested in concurrency for Microsoft platforms, and .NET in particular, I'm happy to report some fresh announcements: PFX is for .NET concurrency development, but of course we are (and personally I am) working on native development tools, including for C++ specifically, that are at least as exciting. Stay tuned here for future news. In the meantime, enjoy these bits and the resources and discussion on the Parallel Computing developer center and forums.
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"CLR 2.0 memory model" - it was quite interesting to know that CLR's memory model is not specified yet but Java's is.
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http://news.google.com/?ned=us&ncl=1121846917
Упомянутые в предыдущем посте "Cluster Computing and MapReduce Mini Lecture Series" - часть этой инициативы. Все курсы находятся здесь:
- http://code.google.com/edu/content/parallel.html
Где раздобыть железа не университетам - пока не ясно.
Насколько Amazon EC2 может подойти?
P.S. Не эта ли инициатива помогла акцииям Google подрости на днях?
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http://gatekeeper.dec.com/pub/DEC/SRC/research-reports/abstracts/src-rr-122.html
Interesting to read in general and about not using reentrant mutexes in particular:
A way to satisfy condition (2) is to use reentrant mutexes, that is, mutexes that do not deadlock when re-locked by the “same” thread (for example, see [Forté 1994]). On one hand, this solution is too liberal, because it allows a method to call an arbitrary method of a different object, which then can call back a method of the present object without deadlocking. This goes well beyond our simple desire that a method should be allowed to call its siblings: it may make objects vulnerable to unexpected activations of their own methods, when other methods have not yet finished reestablishing the object’s invariants. On the other hand, this solution may also be too restrictive because the notion of “same” thread is normally restricted to an address space. If we want to consider control threads as extending across sites, then an implementation of reentrant locks might not behave appropriately.
We solve this dilemma by adopting an intermediate locking strategy, which we call self serialization, based on the notion of self-inflicted operations described in section 3.4. Serialized objects have an implicit associated mutex, called the object mutex. An object mutex serializes the execution of selection, update, cloning, and delegation operations on its host object. Here are the simple rules of acquisition of these object mutexes:- External operations always acquire the mutex of an object, and release it on completion.
- Self-inflicted operations never acquire the mutex of their object.
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"A state is (PC, stack). A concurrent program is (PC, stack)+." - просто и доходчиво излагает Rob Pike. И email у него простой - r@google.com. :)
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From http://binkley.blogspot.com/2007/06/all-dancing-all-singing-locksmith.html
This is a list of features which made me look twice: - Split Lock
- Merge Locks
- Make Class Thread-Safe
- Convert Field to Atomic
- Convert Field to ThreadLocal
- Lock Call-Sites of Method
- Convert Simple Lock to Read-Write Lock
- Convert Read-Write Lock to Simple Lock
- Convert Synchronization Field to Lock
- Split Critical Section
- Shrink Critical Section
- Merge Critical Sections
P.S. "made me look twice" - how to translate this into Russian?
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Hello lot,
Can you suggest some comprehensive multi threading reference book in English with more Windows then POSIX orientation?
Thank you in advance.
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Here is an interesting blog about parallel programming: Thinking Parallel
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Here is an example of using transactions to deal with registry and NTFS in Windows Vista on codeproject. Article called "Vista KTM: Transaction Management in Vista and Beyond ..." By Warren Stevens.
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At very long last Microsoft has been added routines to WinAPI to deal with registry and file system with using of transactions. New transaction API requires Windows Vista or Windows Server "Longhorn". For example one can see RegOpenKeyTransacted routine in MSDN. Here is list of transacted functions to work with file system. In my opinion such functions should be added from the beginning at least for registry.
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I'll try to write something on it to wake up some interest...
ScalPL is a modern programming language thought for writing readable concurrent programs. It doesn't mater whether it's on shared memory, clusters or grid - the program language only describes the flow of the program and the dependencies between sequential (atomic) processes. It will be the task of a compiler to decide how the synchronization is done (mutex, sockets, ...) or how the data is shared.
As an analogy, its creator, David DiNucci tells that at the beginning the programming was thought to be sequential, and instructions were written from up to down (remember any assembler program...). Not too late, came program languages with specific syntax for loops, breaking the sequential old style. The programmers added a new dimension to the programs: the indentation. David adds even another dimension to the programs: a dependency layout between tasks and shared data.
After reading for months his work, I think I understand quite well ScalPL. But I must admit, that the first weeks it was very difficult to me to understand his article Introduction to ScalPL and L23. Now I think that I cannot think of almost any limit programming with ScalPL - but it requires adapting the programs to its syntax; it's not strange that we are already used to mutexes, semaphores, signals, mixed with sequential programs running on multiple threads.
ScalPL is based on Software Cabling; SC is based on F-Nets. I recommend you reading the following, where each complements each other:
Introduction to ScalPL and L23
Towards a Max Benefit, Min Cost, Parallel/Grid Programming Model - Slides, but very helpful.
Tolerant (Parallel) Programming with F-Nets and Software Cabling
F-Nets and Software Cabling: Deriving a Formal Model and Language for Portable Parallel Programming
Google scholar may help finding more articles, but I think only David DiNucci wrote about that. Having an IEEE account will help finding some few more interesting papers to read.
The bad point of all that is that there isn't any editor for ScalPL, neither is a compiler. Amazed by the possibilities of the language, I decided to start writting a compiler of a text-written scalpl. It's not a big success, but I can almost run a very simple subset of the language. I don't have many time to code, but I think often on it - so I hope I can improve it from time to time. Once it's usable for anyone, I'll make a post at least here.
Ah, a new mail list has been created for discussing on ScalPL: scalpl@yahoogroups.com (scalpl-subscribe@yahoogroups.com iirc for getting in)
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I never had in mind that I should use volatile in certain cases...
Here is a nice article from DrDobb's portal on that: http://www.ddj.com/dept/cpp/184403766
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Igor Odintcov wrote about deadlocks handling in his book "Professional programming. System approach". Here is my free translation from russian:
There are four necessary conditions for deadlock to appear:
1. Condition of mutal execution (threads require exclusive resource ownership).
2. Condition of waiting (threads hold some owned resource and wait to own other one).
3. Condition of undistributed resources (resource cannot be taken away while it will not be released by owner thread).
4. Condition of cycled waiting (There are circle of threads where one thread holds one or more resources which is required by next one).
So that there are four main methods to operate with deadlocks:
1. Full ignorance of a problem ("straus algorithm"). Real operation systems don't strive against deadlocks because it is quite enough of resources.
2. Deadlock prevention. To prevent deadlock it is enough to break at least one condition.
- First condition is natural for some kind of resources (such as input\output devices) and so that this condition cannot be broken in some cases.
- To broke second condition a thread has to acquire all resources at once. Effectiveness of a system can become much worse.
- To broke third condition thread has to release all held resources if it is refused to acquire some more resources and try to acquire this resources after a time. But the most part of the work can be lost in this case.
- To broke fourth condition one has to introduce linear order of resources, and allow holding resources only in order where no deadlocks possible. This method requires some more additional expenditure to store information about resource types and order of resource instances.
3. Deadlock avoidance. This method provides rational resources acquiring by rational rules. The most known algorithm of deadlock avoidance is algorithm of banker.
- Algorithm imitates banker actions which has source of capital, grants a loans and receive a payments. This algorithm is proposed by Deykstra.
- The system state is stable if it can process all tasks of all users in finite quantity of time. The system will process only those tasks which will leave system in stable state.
- There are two serious limitation of this method: each thread has to know how many resources it need beforehand and in each moment of a time holds only one resource. This algorithm is inapplicable on practice because of inefficiency (thread has constantly recalculate quantity of required resources).
4. Deadlock detection. This method supposes that deadlock can happen, detect deadlocked threads and resources and try to resolve this situation.
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I have updated my lwsync library. Monitor Waiting Cancellations feature was added.
Also it was reviewed and approwed on Code Project, so new article location is here. Note that it still request for comments or proposals.
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I have found here in MSDN a new synchronization stuff which will be available in Windows Vista and Windows Server "Longhorn".
There will be added the following functionality:
- Read/Write Lock and Condition Variables (at long last!). Condition variable will have an ability to sleep with critical section or RWLock object.
- Some Init Once stuff.
- Some additional Interlocked functions such as InterlockedBitTestAndSet\Reset and InterlockedCompare64ExchangeAcquire128
- Private Namespaces.
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There is an implementation of pthread interface for Win32 platform.
It will be very interesting to test if I can cancel some thread blocked with system implementation of accept() or read() with Win32 version of pthread_cancel()
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