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

[uBLAS] Matrix inversion
by Ryan 03 Mar '11

03 Mar '11

I haven't found anywhere in the documentation for a method that does matrix inversion. Does such a method exist but isn't well documented? Ryan

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Re: [Boost-users] [MSM] test if state machine is in a given state /const get_state
by Christophe Henry 03 Mar '11

03 Mar '11

> I considered to use the concept of flags, but then rejected it, simply > because it adds another layer of abstraction, which is great in certain > cases, but also increases the overall complexity. > > In my case i need hardly any properties which span over more than one > state, so i prefer to keep thinks simple for now. It's the constant > struggle to have enough, but not to much abstraction... > > But thanks for the hint, i'll keep that in mind. Hmmm as you can provide every state with a specific tag, I don't see why to develop a less generic, less efficient concept which will be hard to make work for submachines. Am I missing something? >>> 2) Is a const version of "get_state" possible ? And how? >> >> Sure. My mistake. Will be fixed in 1.47. Would you mind opening a >> ticket so I don't forget it? > > done, ticket #5253. Now i'am looking forward to 1.47 ;-) Thanks. Regards, Christophe

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phoenix vs. python
by Neal Becker 03 Mar '11

03 Mar '11

Can I use phoenix lambda in boost::python? Let's see: ------------------------------------ #include <boost/python/module.hpp> #include <boost/python/def.hpp> #include <boost/spirit/home/phoenix.hpp> namespace bp=boost::python; BOOST_PYTHON_MODULE (test_phoenix) { bp::def ("test1", &boost::phoenix::val(1)); } ---------------------------------------- Any suggestions? Here's what gcc-4.5 says: In file included from test_phoenix.cc:2:0: /usr/local/src/boost_1_46_0.hg/boost/python/def.hpp: In function ‘void boost::python::def(const char*, Fn) [with Fn = boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::reference_eval, boost::fusion::vector<boost::phoenix::value<int>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >]’: test_phoenix.cc:8:44: instantiated from here /usr/local/src/boost_1_46_0.hg/boost/python/def.hpp:91:5: error: cannot pass objects of non-trivially-copyable type ‘struct boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::reference_eval, boost::fusion::vector<boost::phoenix::composite<boost::phoenix::reference_eval, boost::fusion::vector<boost::phoenix::value<int>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> >, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >’ through ‘...’ In file included from /usr/local/src/boost_1_46_0.hg/boost/python/def.hpp:11:0, from test_phoenix.cc:2: /usr/local/src/boost_1_46_0.hg/boost/python/make_function.hpp: In function ‘boost::python::api::object boost::python::make_function(F) [with F = boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::reference_eval, boost::fusion::vector<boost::phoenix::value<int>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >]’: /usr/local/src/boost_1_46_0.hg/boost/python/def.hpp:82:61: instantiated from ‘boost::python::api::object boost::python::detail::make_function1(T, ...) [with T = boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::reference_eval, boost::fusion::vector<boost::phoenix::value<int>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >]’ /usr/local/src/boost_1_46_0.hg/boost/python/def.hpp:91:5: instantiated from ‘void boost::python::def(const char*, Fn) [with Fn = boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::reference_eval, boost::fusion::vector<boost::phoenix::value<int>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >]’ test_phoenix.cc:8:44: instantiated from here /usr/local/src/boost_1_46_0.hg/boost/python/make_function.hpp:104:60: error: no matching function for call to ‘get_signature(boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::reference_eval, boost::fusion::vector<boost::phoenix::value<int>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >&)’

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Async_accept
by Marco Piacentini 03 Mar '11

03 Mar '11

Hi guys... Reading docs, I understand that acceptor.async_accept(), accept a connection and immediately return, so the acceptor can accept another concurrent connection request...and in the meanwhile the handler can process the request...it's right? I need to make a server that listen connection requests, and create a separate process (child) to handle each of them, so it can be still waiting a new connection. The classic MultiProcess Server. Can I do this simply using the async_accept, without create new process?or I'm missing something? Thanks...

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Re: [Boost-users] [MSM] test if state machine is in a given state /const get_state
by Christophe Henry 03 Mar '11

03 Mar '11

Hi Jan, > i am working with the Boost 1.45 Meta State Machine, using both > orthogonal regions and submachines. Overall, i am very happy with this > library. Cool :) > But i am looking for a nice way to check if a state machine (e.g. > instance mAvail of class AvailFSM) is in a given state, for example i > would like to write something like this: > > assert(isInState(mAvail, AvailFSM::UpstreamAvailable())); > > I didn't find something like "isInState" provided by the MSM library, so > i came up with the following implementation: > > template <class FSM, class StateType> > bool isInState(const FSM& p, const StateType& s) > { > int stateId = boost::msm::back::get_state_id<typename > FSM::stt,StateType>::value; > > for (int i=0; i < FSM::nr_regions::value; ++i) > { > if(p.current_state()[i] == stateId) > { > return true; > } > } > return false; > } > > This works well for simple state machines and orthogonal regions, but > not for submachines. Does any one knows a way to extend the above code > to work with submachines? Hmmm not a bad idea indeed, I need to think about it, but in the meantime I have another (and I think faster) solution. See below. <snip> > Currently i am using the following workaround: > > assert(isInState(mAvail, AvailFSM::UpstreamAvailable())); > assert(isInState(mAvail.get_state<AvailFSM::UpstreamAvailable&>(), > AvailFSM::UpstreamAvailable::Primary())); > > I consider this solution ugly not only because of its lengthiness, but > also because "get_state" isn't a const function. Unfortunately i'am not > deep enough into the template magic to tell if a const implementation of > "get_state" is possible. Can anyone help me out ? Usually, if you want to ask "isInState", you actually mean "is my fsm in such a state that a property is true?". Next, what you will want is: assert(isInState(mAvail, AvailFSM::UpstreamAvailable()) || isInState(...) && !... ); And this can pretty fast get much uglier as you need more and more conditions. To that aim, MSM offers the concept of flags, allowing you to flag a state with a certain property. You can then check if the property is true with, say: if (mAvail.is_flag_active<UpstreamOk>()) ... Please have a look at (for 1.46 but any released version of MSM can do this): http://www.boost.org/doc/libs/1_46_0/libs/msm/doc/HTML/ch03s02.html#d0e1110 Ah and it also works on submachines. > So, to sum up, i have two questions: > 1) How to implement something like "isInState" that even works on > submachines, if possible ? Would the offered solution satisfy your need? > 2) Is a const version of "get_state" possible ? And how? Sure. My mistake. Will be fixed in 1.47. Would you mind opening a ticket so I don't forget it? > best regards, > jan Best regards, Christophe

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[phoenix][v3] Evaluating a terminal expression in the custom actions class.
by Alexander Ospin 03 Mar '11

03 Mar '11

Is it possible to evaluate terminal and custom_terminal expressions in the some custom actions class? For instance how to implement "terminal_eval" to print something in the following code? #include <boost/phoenix/phoenix.hpp> #include <iostream> using namespace boost; struct actions { template <typename Rule, typename Dummy = void> struct when; }; template <> struct actions::when<phoenix::rule::terminal> : phoenix::call<terminal_eval> {}; int main() { int var = 11; phoenix::eval(phoenix::val(var), phoenix::context(int(), actions())); return 0; } I've tried to use the following form, but encountered some compiler errors: (GCC-4.2.1[FreeBSD], boost and phoenix were taken from SVN, latest versions) struct terminal_eval { typedef void result_type; template <typename Context, typename Expr> result_type operator ()(Context const &ctx, Expr const &expr) { std::cout << "terminal" << std::endl; } }; ../../../../boost.phoenix/boost/phoenix/core/call.hpp:32: error: invalid use of incomplete type 'struct boost::phoenix::detail::call_impl<terminal_eval, const boost::phoenix::actor<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int>, 0l> >&, const int&, const actions&, 0l>' ../../../../boost.phoenix/boost/phoenix/core/call.hpp:22: error: declaration of 'struct boost::phoenix::detail::call_impl<terminal_eval, const boost::phoenix::actor<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int>, 0l> >&, const int&, const actions&, 0l>' ../../../../boost/boost/proto/transform/call.hpp:315: error: no type named 'result_type' in 'struct boost::proto::switch_<boost::phoenix::meta_grammar>::impl<const boost::phoenix::actor<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int>, 0l> >&, const int&, const actions&>' ../../../../boost/boost/proto/transform/call.hpp:320: error: no type named 'result_type' in 'struct boost::proto::switch_<boost::phoenix::meta_grammar>::impl<const boost::phoenix::actor<boost::proto::exprns_::expr<boost::proto::tag::terminal, boost::proto::argsns_::term<int>, 0l> >&, const int&, const actions&>' The same situation with the phoenix::ref and custom_terminal rule.

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[date_time] Concurrent posix_time streaming crashes under MinGW-32
by Jim Bell 03 Mar '11

03 Mar '11

The attached program crashes under MinGW-32 (gcc-4.4), but works under VC8. It does concurrent streaming of posix_time::ptime values to a std::ostringstream. Mutexing the ostringstream from construction to destruction keeps it from crashing, but that shouldn't have to be done for independent streams. Mutexing just the ptime insertions makes it run longer, but it still crashes. I'm posting it here instead of taking it straight to Trac to see if anyone has input. Could it be related to <https://svn.boost.org/trac/boost/ticket/3961> or <https://svn.boost.org/trac/boost/ticket/3369>? Building: MinGW: g++ -DBOOST_THREAD_USE_LIB DTConcur.cpp -IC:\Software\Open\lib\boost_1_45_0\ -DWIN32 -D_WINDOWS -LC:\Software\Open\lib\boost_1_45_0\mgw44\lib -mthreads -g -frtti -fexceptions -mthreads -Wall -lstdc++ -lmingw32 -o DTConcur -lboost_thread-mgw44-mt-s-1_45 VC8: cl DTConcur.cpp /IC:\Software\Open\lib\boost_1_45_0\ /MT /D BOOST_THREAD_USE_LIB /GR /EHsc /D "WIN32" /D "_WINDOWS" /FeDTConcur.exe /link /LIBPATH:C:\Software\Open\lib\boost_1_45_0\msvc8\lib

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[preprocessor] have macro do different things based on structure of its argument
by Nathan Ridge 03 Mar '11

03 Mar '11

Hello, I would like to write a macro MY_MACRO(x) that does different things based on the structure of its input, e.g. something different for each of the following forms: MY_MACRO(x) // a single token MY_MACRO((x, y)) // a parenthesized list of two tokens MY_MACRO((x, y, z)) // a parenthesized list of three tokens MY_MACRO(x y) // two tokens MY_MACRO(x y z) // three tokens MY_MACRO(x = y) // three tokens with the second one being something specific Are any of these possible? Thanks, Nate.

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ASIO / IO Completion Ports (Windows)
by asif saeed 02 Mar '11

02 Mar '11

Hi, I wonder if ASIO on Windows also implements IO Completion ports. I think this is called Proactor, right? I would be thankful if you point me to the right direction. Also, any links/examples of using ASIO with Boost::Thread (or TR1) would be very helpful. I am a newbie on ASIO & Boost Thread. Sincerely / Asif

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Re: [Boost-users] [GIL] gray pixel iterator in generic algorithm
by Robert Lupton the Good 02 Mar '11

02 Mar '11

> With this, the unit test for my gray opening function with an unscaled float image now compiles and works fine. Does this mean that you have some clean way to handle gil images that don't automatically scale into [0,1]? If so, can we have it pushed into the next boost release? I have a clunky version of this that I'm not proud of, but I certainly need. I'm an astronomer, and the values in my images (unsigned short, int, float) are directly related to the number of photons detected so scaling is a real problem. R

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