July 2011 - Boost-users - lists.preview.boost.org

[Python] Handling std::vector and boost::tuple
by Johan Råde 27 Jul '11

27 Jul '11

The following code fails with the error message: "Boost.Python.ArgumentError: Python argument types in m.f(list) did not match C++ signature: ..." How do I make it work? Do I have to write a custom translator? C++: void f(const vector<tuple<double, string, bool> >& x); BOOST_PYTHON_MODULE(m) { def("f", &f); } Python: import m m.f([(4.3, 'abc', True)]) Thank you, Johan Råde

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boost::units units symbols/names
by Michael Powell 26 Jul '11

26 Jul '11

Boost::units users, How do I get at the unit symbol or name? I think this type thing would be essential when receiving and parsing textual quantities from a client side application. So say I am given "1.0 in" or "2.3 m/s^2" and so on, and be able to translate that into the appropriate compile-time dimensional quantity. Thanks... Regards, Michael

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[cross-compiling]
by Wilde, Donald S 26 Jul '11

26 Jul '11

We have a somewhat tricky cross-compile, and I'm hoping I can get some feedback to help me be sure that I'm doing this right. In my user-config.jam, I (think I) need to put the following line: Using gcc : 4.5.1 : : "/path/to/target/compiler" <compileflags> -I/path/to/sdk/includes <cxxflags> -std=c++0x <cflags> -Wall -march=atom Does that sound right? Does boost depend on standard precompiled libraries like libstdc++.so? I've been bit by having the system crash hard in different places, and I suspect that sometimes this is caused by the fact that the host is i686 linux and the target is an atom-based SoC with custom linux libraries. Boost wants to pull them from the host, so I need to tell it everything it should NOT pull silently. Correct? Do I also need a <linkflags> -L/path/to/target/lib/directory? -- Don Wilde DHG | TSPO 480-552-3792 donald.s.wilde(a)intel.com

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[Review] Lockfree review: two more days left
by Hartmut Kaiser 26 Jul '11

26 Jul '11

Hi all, We have two more days left for the review of Tim Blechmann's Lockfree library. If you're interested in this library, please consider contributing a review! Please see the original (slightly corrected) announcement below: ----------------------------------------------------- About the library: Boost.Lockfree provides implementations of lock-free data structures. Lock-free data structures can be accessed by multiple threads without the necessity of blocking synchronization primitives such as guards. Lock-free data structures can be used in real-time systems, where blocking algorithms may lead to high worst-case execution times, to avoid priority inversion, or to increase the scalability for multi-processor machines. The following data structures are provided: - boost::lockfree::fifo, a lock-free fifo queue - boost::lockfree::stack, a lock-free stack - boost::lockfree::ringbuffer, a wait-free single-producer/single-consumer ringbuffer. The library is accessible from here: http://tim.klingt.org/boost_lockfree.tar.gz. Boost.Lockfree depends on C++0x atomics. They are not well supported with current compilers yet. For this reason Boost.Lockfree depends on the *unreviewed* Boost.Atomic library, that emulates C++0x atomics for C++98. This review is about Boost.Lockfree and not about Boost.Atomic, although it is included in the tarball and the git repository. If Boost.Lockfree will be accepted, it won't be merged into trunk before Boost.Atomic is accepted. --------------------------------------------------- Please always state in your review, whether you think the library should be accepted as a Boost library! Additionally please consider giving feedback on the following general topics: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? Regards Hartmut Review Manager

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[boost-users] [geometry] segment concept
by Sergei Politov 26 Jul '11

26 Jul '11

Hello, I play with new boost geometry library. There is thing that I don't understand, possible it is bug. I'm trying to register segment concept. It is struct with fields named "point1" and "point2", that represents endpoints of this segment. I've specified tag, point_type, indexed_access for this struct. And length works fine. But intersection requires that this struct contains fields named "first" and "second". I'm new to this library, so I don't know whether it is bug in library or my code. I've attached minimal c++ file that reproduces the problem. If I uncomment //#define point1 first //#define point2 second all compiles and works fine. Best Regards, Sergey

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[Serialization] Writing an old version of a class
by Don 26 Jul '11

26 Jul '11

I apologize if this is a duplicate posting. I sent this 2 days ago, and it appears in the archives, but I never received it back from the list and there have been no replies, so I am posting it again. Using boost serialization, I would like to be able to write an old version of a class, so that I can save data in an "old" format to allow other users with an old version of my program to read the file. I see from the archives that this has come up before, and Robert Ramey indicated it was doable and on the todo list, but I don't see it in the release notes or documentation. Did anything every come of this? Or, has anyone else done this? Any suggestions on how to accomplish this? Thanks, Don

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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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