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[multiindex] Ordered index corruption
by Chris Jewell 26 Jul '11

26 Jul '11

Hi All, I have a problem with a multiindex ordered_non_unique index becoming corrupted :( I am working with a multiindex that stores class objects of type Individual: class Individual { double I_; double id_; public: double getId() const; double getI() const; void setId(const std::string id); void setI(const double I); } boost::multi_index_container< Individual, indexed_by< random_access< tag<bySeq> >, hashed_unique< tag<byId>, const_mem_fun<Individual,string,&Individual::getId> >, ordered_non_unique<tag<byI>, const_mem_fun<Individual,double,&Individual::getI> > > > I have an algorithm that works on these data, using Individual::I to calculate a summary value across the whole dataset. An Individual i is then chosen at random, and i.I updated using the multiindex::modify method with a functor: struct modifyI { modifyI(double newI) : newI_(newI) {} void operator()(Individual& i) { i.setI(newI_); } private: double newI_; }; This calculation is then repeated many times. The actual calculation is done in parallel using MPI (Boost::MPI on top of OpenMPI), with the final reduction being broadcast to all processes. This enables each processor to make the same change to its copy of the multiindex. In *theory* this should mean that each process has a complete replicate of the multiindex. However, I am finding that the ordered_non_unique index is becoming corrupted in that the ordering (strict less than on Individual::I) gets messed up for a few (c. 2 or 3) of the elements. Essentially, it appears that small blocks of the index get swapped round. This is not occurring simultaneously on all processes, which is odd because the same multiindex::modify method is called for each process with the same arguments. Can anyone suggest a way I can move forward on trying to debug this? Thanks, Chris -- Dr Chris Jewell Department of Statistics University of Warwick Coventry CV4 7AL UK Tel: +44 (0)24 7615 0778

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Pointer "boundary checker" class or tools?
by Hoe-Phuan Ng 26 Jul '11

26 Jul '11

Hello: I a new to C++. Have not use it yet. For a long time I was wondering if there is a way to automatically check if pointer has creep out of its "known area of access" in memory. Obviously such tool to check pointer would be really slow or too slow for release codes since we want to check pointer location at each pointer access, read or write. Is there such a tool or class to do Pointer "boundary checker" during debug? Thanks. HP

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Odd Warning in transform_iterator.hpp ?
by John M. Dlugosz 26 Jul '11

26 Jul '11

I'm using the current Boost library on Microsoft Visual Studio 2005. I'm getting a warning on line 121 of transform_iterator.hpp, complaining "returning address of local variable or temporary". The line in question is the body of this function: typename super_t::reference dereference() const { return m_f(*this->base()); } My m_f supplied to the template is ordinary enough; it returns a value. The exact same situation in a unit test gives no complaint! Any idea what this is all about?

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boost::python::long_ issue
by Pavel Grafov 26 Jul '11

26 Jul '11

Hello, guys! In order to check how does boost::python works with long numbers I found this snippet of code (found it on the boost documentation page - http://www.boost.org/doc/libs/1_42_0/libs/python/doc/v2/long.html) namespace python = boost::python; // compute a factorial without overflowing python::long_ fact(long n) { if (n == 0) return python::long_(1); else return n * fact(n - 1); // here points the compiler } However, I cannot compile it - the compiler says "error: conversion from ‘boost::python::api::object’ to non-scalar type ‘boost::python::long_’ requested", pointing to the line marked. What am I doing wrong? Supposing multiplying is forbidden, is there another way to create a boost::python::long greater than the greatest long (2**32 - 1)? -- Best regards, Pavel.

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HasPlus
by Robert Jones 26 Jul '11

26 Jul '11

Hi All I'm clutching at straws here, so this may be a complete fiction, but I seem to recall mention of purely syntactic concept definitions as part of the now-abandoned C++0x concept proposal. Things like hasPlus. Maybe I've just made this up! Does any such thing exist in boost anywhere? Maybe as a concept check or type trait? Thx - Rob.

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[Thread] Assertion on mutex when using multiple threads and mutexes
by Tim van den Kerkhof 26 Jul '11

26 Jul '11

Hi all, As a part of a project I'm writing a logger function. This logger function sends an e-mail when the program wants to log something. Since it has happened that the SMTP server was non responsive, I've decided to do the sending of the mails in a separate thread. This thread reads messages from an std::deque which is filled by the logging function. The thread is setup as follows: while (!boost::this_thread::interruption_requested()) { EmailItem emailItem; { boost::unique_lock<boost::mutex> lock(mMutex); while (mEmailBuffer.empty()) mCond.wait(lock); bufferOverflow = mBufferOverflow; mBufferOverflow = false; nrOfItems = mEmailBuffer.size(); if (nrOfItems> 0) { emailItem = mEmailBuffer.front(); mEmailBuffer.pop_front(); } } if (nrOfItems> 0) { bool sent = false; while(!sent) { try { ..... Do something with the message ..... { boost::this_thread::disable_interruption di; boost::lock_guard<boost::mutex> lock(mLoggerMutex); mLogFile<< emailItem.mMessage<< std::endl; } sent = true; } catch (const std::exception&e) { // Unable to send mail, an exception occurred. Retry sending it after some time sent = false; boost::this_thread::sleep(boost::posix_time::seconds(LOG_WAITBEFORE_RETRY)); } } } } The function log() adds a new message to the deque (mEmailBuffer) as follows: { boost::lock_guard<boost::mutex> lock(mMutex); mEmailBuffer.push_back(e); mCond.notify_one(); } When the main program exits, the destructor of the logger object is called. This is where it goes wrong, the application crashes with an error: /usr/include/boost/thread/pthread/mutex.hpp:45: boost::mutex::~mutex(): Assertion `!pthread_mutex_destroy(&m)' failed. The destructor merely calls an interrupt on the thread and then joins it: mQueueThread.interrupt(); mQueueThread.join(); In the main program, I use multiple different classes which make use of boost threading and mutex as well, could this cause this behaviour? Not calling the destructor of the logger object results in no errors, as does using the logger object and not doing anything else. My guess is I am doing something very wrong, or there is a bug in the threading library when using multiple threads divided over several classes. Does anyone have a idea what the reason for this error might be? Regards, Tim van den Kerkhof

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boost::units implicit conversions
by Michael Powell 25 Jul '11

25 Jul '11

Boost::units users, I have gotten my feet wet with boost::units over the past several days and starting to get the hang of it, dimensions, quantities, and units, and so forth. Now I would like to start thinking more in terms of how these units-based calculations should be used by the rest of our application. Of primary concern is to receive a quantity of dimension from the application in a specified unit and to be able to perform the calculations. One concept I've been wondering about is whether there is any value in converting units to a base unit for purposes of IPC (interprocess communication), saving to or loading from files, or that sort of thing. In this way we will know that if we see a quantity of length dimension, for instance, we can always expect the value to be presented in terms of, let's say, meters. My question concerning calculations is something along these lines: how does boost::units treat a quantity<dimension> when facilitating dimensioned calculations? Or is it on us as developers to ensure that an appropriate unit-conversion is taking place somewhere along the way when we are ready to interpret the result for display, report, or whatever? Let me know if I can clarify at all, because I am a little fuzzy along these lines at the moment. Thank you... Regards, Michael

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[Fusion] issues when adapting an existing structure
by Sean Farrow 25 Jul '11

25 Jul '11

Hi: I'm trying to adapt a structure for use with spirit. I have the following code: struct JAWSFunction { std::wstring FunctionType; std::wstring Description; std::wstring Synopsis; std::string ReturnType; std::vector<std::pair<std::wstring, std::wstring> > Parameters; }; //tell boost.Fusion about the JAWSFunction structure to allow it to be used with spirit. BOOST_FUSION_ADAPT_STRUCT(JAWSFunction, (std::wstring, FunctionType)(std::wstring, Description)(std::wstring, Synopsis)(std::wstring, ReturnType)(std::vector<std::pair<std::wstring, std::wstring> >, Parameters)) If I compile this with the std::vector<std::pair<std::wstring, std::wstring> > taken out, this works fine. However replacing the vector of pairs doesn't compile. How can I get this to work? Any help appreciated. Cheers Sean.

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boost::units us system
by Michael Powell 25 Jul '11

25 Jul '11

Boost::units users, I am looking for a system which gathers the U.S. units of measure. I notice, for instance, that SI has a system. Are there any plans in the works to introduce a US system? If not, how hard would that be? There are base units, for instance. So it would be a matter of setting up the appropriate systems? **or** what approach have boost::units users taken in the past when broaching the US-SI unit conversion question? Thank you... Regards, Michael

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boost::units unit proposal
by Michael Powell 25 Jul '11

25 Jul '11

Boost::units developers / users, I need to specify a U.S. Barrel (bbl) for purposes of performing conversions and so forth. First, does this definition look about right? Second, how does one propose an addition to the units code base? Note, I'm not quite sure how the 2^3 scaling from gallon to pints works in terms of scaling from barrel to gallons, or pints for that matter, so I am assuming that gallon can be the base unit for barrel and call it good. Thoughts, questions, concerns? namespace us { typedef scaled_base_unit<gallon_base_unit, scale<42> > barrel_base_unit; } // namespace us template<> struct base_unit_info<us::barrel_base_unit> { static const char* name() { return("bbl (U.S.)"); } static const char* symbol() { return("bbl"); } }; Thank you... Regards, Michael

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