- Boost-users - lists.boost.org

using ublas to solve linear systems?
by deane_yang 12 Nov '02

12 Nov '02

I'm trying to see if I can use ublas to solve a linear system of equations. Digging through the documentation, I find a description of a function called 'solve" that says "Solves a linear equation for a triangular matrix." There is also a formula, B = solve(A, B, tag) <------> B <- A-1 B But I just don't know what any of this means (even though I am a mathematician and quite fluent in linear algebra). So a) can ublas be used (without me implementing any additional algorithms) to solve a linear system of equations? b) what exactly does the function solve do?

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RE: [Boost-Users] BUG: counted_base::release
by Per Kristensen 12 Nov '02

12 Nov '02

This is a constructed test case which should illustrate the problem. The bug is only a problem if you access data members of the counted_based object after the call to delete. So you can live happy without knowing anything about the bug if you never do that. //sourcecode begin #include "boost/shared_ptr.hpp" #include "boost/weak_ptr.hpp" class foo { public: void setWeak(boost::shared_ptr<foo> s) { w = s; } private: boost::weak_ptr<foo> w; //the desctuction of this member will delete the counted_based object }; class deleter { public: deleter() :lock(0) {} ~deleter() { assert(lock==0); //assert if destructor is called when we are executing } void operator() (foo *p) { ++lock; //lock the object from destruction within this operation delete p; --lock;//unlock the object } private: int lock; }; void main() { boost::shared_ptr<foo> s(new foo,deleter()); s->setWeak(s); s.reset(); } //source code end -----Original Message----- From: Peter Dimov [mailto:pdimov@mmltd.net] Sent: 11. november 2002 21:43 To: Boost-Users(a)yahoogroups.com Subject: Re: [Boost-Users] BUG: counted_base::release From: "perkristensennettest" <per.kristensen(a)nettest.com> > To me it seems like a bug, that the weak_count in > counted_base::release is decremented before the call to dispose. See > below [...] > > If the call to dispose() indirectly calls weak_release there is an > error as weak_release will decrement the --weak_count and may > destruct the counted_base object. This will happen if you have an > class C with a member of type weak_ptr<C>. Do you have a test case that breaks? Info: < http://www.boost.org> Wiki: < http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> . [Non-text portions of this message have been removed]

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uBLAS Matrix Multiplication
by Hickman, Greg 12 Nov '02

12 Nov '02

Why isn't there an overloaded matrix_expression operator* (const matrix_expression&, const matrix_expression&); for peforming matrix multiplication? Greg Hickman

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compose function objects
by daniel szymanski 11 Nov '02

11 Nov '02

hi, i've a question regarding the compose function objects. i was wondering if there is something like compose_f_x_gy etc? i know there's only the compose_f_gx_hy function object. but then i would need g(x) = x, so my question: is there another way to get the same result like using g(x) = x or writing a compose_f_x_gx? thanks, daniel

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RE: [Boost-Users] compose function objects
by Mark Storer 11 Nov '02

11 Nov '02

I'd think you could write a toy function (inline and all that) to do just that, then pass it in as the 'gx' param. I'd be disappointed if it didn't vanish during optimization, leaving just the 'x'. --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard;

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BUG: counted_base::release
by perkristensennettest 11 Nov '02

11 Nov '02

To me it seems like a bug, that the weak_count in counted_base::release is decremented before the call to dispose. See below //source code begin void release() // nothrow { long new_use_count; long new_weak_count; { #ifdef BOOST_HAS_THREADS mutex_type::scoped_lock lock(mtx_); #endif new_use_count = --use_count_; new_weak_count = --weak_count_; //this is a bug } if(new_use_count == 0) { dispose(); //the this object may be deleted here } if(new_weak_count == 0) { // not a direct 'delete this', because the inlined // release() may use a different heap manager self_deleter_(this); } } //source code end If the call to dispose() indirectly calls weak_release there is an error as weak_release will decrement the --weak_count and may destruct the counted_base object. This will happen if you have an class C with a member of type weak_ptr<C>. As I see it the decrement of weak_count should be moved to after the dispose call. see below: //source code begin void release() // nothrow { long new_use_count; long new_weak_count; { #ifdef BOOST_HAS_THREADS mutex_type::scoped_lock lock(mtx_); #endif new_use_count = --use_count_; //do not decrement weak_count here } if(new_use_count == 0) { dispose(); } { #ifdef BOOST_HAS_THREADS mutex_type::scoped_lock lock(mtx_); #endif new_weak_count = --weak_count_; } if(new_weak_count == 0) { // not a direct 'delete this', because the inlined // release() may use a different heap manager self_deleter_(this); } } //source code end ????

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RE: [Boost-Users] Strange bug / MSVC 6.5 / Boost 1.29 / utility_f wd.hpp
by Tom Matelich 11 Nov '02

11 Nov '02

Here's a short example: #include <boost/smart_ptr.hpp> #include <iostream> namespace ZSystem { namespace Leg { enum Type { INLET = 1, OUTLET = 2 }; } } std::ostream& operator<<(std::ostream&, ZSystem::Leg::Type); #include <boost/utility.hpp> Not sure whats going on here, I just started with a broken compile and reduced it to here. > -----Original Message----- > I haven't tracked down what include order is causing this, > but I'm getting: > > c:\dev\opt\include\boost/utility_fwd.hpp(21) : fatal error > C1001: INTERNAL > COMPILER ERROR > (compiler file 'msc1.cpp', line 1794) > Please choose the Technical Support command on the > Visual C++ > Help menu, or open the Technical Support help file for more > information > ----------------------------------------------------------------------- DISCLAIMER: Information contained in this message and/or attachment(s) may contain confidential information of Zetec, Inc. If you have received this transmission in error, please notify the sender by return email. -----------------------------------------------------------------------

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Strange bug / MSVC 6.5 / Boost 1.29 / utility_fwd.hpp
by Tom Matelich 11 Nov '02

11 Nov '02

I haven't tracked down what include order is causing this, but I'm getting: c:\dev\opt\include\boost/utility_fwd.hpp(21) : fatal error C1001: INTERNAL COMPILER ERROR (compiler file 'msc1.cpp', line 1794) Please choose the Technical Support command on the Visual C++ Help menu, or open the Technical Support help file for more information Of course MSVC doesn't have header include tracing. I've been working around it with spurious includes of <boost/utility/base_from_member.hpp>. Any ideas? Thanks, Tom ----------------------------------------------------------------------- DISCLAIMER: Information contained in this message and/or attachment(s) may contain confidential information of Zetec, Inc. If you have received this transmission in error, please notify the sender by return email. -----------------------------------------------------------------------

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gcc bug
by wugui 11 Nov '02

11 Nov '02

FreeBSD 4.6-STABLE gcc version 2.95.3 20010315 (release) [FreeBSD] 1. CXXFLAG = -Wall -g -pthread -D_THREAD_SAFE is ok 2. CXXFLAG = -Wall -ggdb -pthread -D_THREAD_SAFE boost_1_28_0/boost/function/function_base.hpp:155: Internal compiler error in `output_die', at dwarf2out.c:5433 Please submit a full bug report. See <URL:http://www.gnu.org/software/gcc/bugs.html> for instructions.

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Is this shared_ptr usage okay?
by Hickman, Greg 11 Nov '02

11 Nov '02

I'd like to prevent clients from directly creating and deleting instances of a type like 'Bill' below, so Bill's constructor and destructor have been made private to prevent ordinary client access. Since Bill has reference semantics, construction is handled by a static 'Bill::create()' factory method which returns a dynamically allocated Bill instance wrapped in a shared_ptr. Destruction is handled by a private Bill::Deallocator who also happens to be a Friend of Bill (FOB). My question is: Is this an acceptable use of the shared_ptr deallocator, or am I just asking for trouble? Thanks, Greg Hickman //-------------------------------------- #include <boost/shared_ptr.hpp> using namespace boost; class Bill; typedef shared_ptr<Bill> Bill_ptr; class Bill { private: Bill() {} ~Bill() {} struct Deallocator { void operator() (Bill* b) const { delete b; } }; friend struct Deallocator; public: static Bill_ptr create() { return Bill_ptr(new Bill, Deallocator()); } };

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