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Re: Re: Newbie needs pointer to currently executing thread.
by Moore, Dave 11 Apr '02

11 Apr '02

<dick.bridges(a)tais.com> wrote in message news:OFAB9F41E0.6C6A5A14-ON88256B97.005045D8@tais.net... > > I'm implementing the Leader/Followers thread pool pattern - reference > "Pattern-Oriented Software Architecture Volume 2" (Schmidt, et al). > > When a thread is released via notify_one(), it is [assumed to be] in the > "leader" role and stores it's id. A sanity check should be performed to > verify that there is no other thread in the leader role (i.e., > current_leader is "none") before the thread stores it's id there. > > When one of the event sources is signaled and the leader is unblocked, it > must, among other tasks, demote itself (i.e., set the current_leader value > to "none") > and promote one of the followers by notify_one() before continuing to > service the request. Because of the potential for race conditions, > (especially in the context of future program updates, modifications, etc.) > I should enforce the rule that only the leader can promote a follower. > Something along the lines of: current_leader == Thread::this(). > I disagree (about the race condition). Your condition variable is usually used in conjunction with a mutex which protects your shared state's invariants. boost::mutex m; boost::condition c; Invariant: leader != NONE Pseudo-code for leader releasing boost::mutex::scoped_lock l(m); // lock mutex if(TimeForANewLeader) { leader=NONE; c.notify_one(); // Will signal one waiter..... // finish task - MUTEX IS STILL HELD! // } l.unlock(); // Only now will a waiter return from wait(); Pseudeo-code for follower waiting for signal: boost::mutex::scoped_lock l(m); // lock mutex while(Not TimeForANewLeader) { c.wait(m); // Waiting automically releases AND reacquires // the mutex } // When we get here, we know we hold the mutex. // Follower is responsible for "self-promotion" leader=ME; // Start my work as a leader. An important note is that if we reach the while() statement and it IS time for a new leader, then we never wait, we already hold the mutex, and it is safe for us to promote ourselves anyways! Note that for the time being, you'll have to go outside of Boost.Threads for the leader=ME statement because thread objects aren't copyable so leader=boost::thread(); doesn't work to get the current thread. Bill Kempf has indicated that some form of portable thread_id s are coming in a future version. Hope this helps... Dave >

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Streamed input for rational, badbit vs failbit
by aj_dicks 10 Apr '02

10 Apr '02

Is there an error in the declaration of template <typename IntType> std::istream& operator>> (std::istream& is, rational<IntType>& r) in boost.hpp? The lines if (c != '/') is.clear(std::istream::badbit); appear in the function definition, as the format is num/den, so we expect a slash character. However, is setting the stream to bad correct? Shouldn't it be failbit instead? The standard states that badbit indicates a loss of integrity in an input or output sequence (such as an irrecoverable read error from a file); failbit indicates that an input operation failed to read the expected characters, or that an output operation failed to generate the desired characters. Also, to cite precedence from the standard, it stipulates that the std::complex type's extraction operator should call is.setstate(ios::failbit) if bad input is found. What is confusing, however, is that Stroustrup's example input operation for complex sets badbit (section 21.3.5 in the third edition of his bible). So who is right out of: me, rational.hpp, the C++ standard, Stroustrup? Is it more than two of these, and if so, where is my misunderstanding?

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newbie q: - make errors on Solaris (testing boost/regex)
by dz_nyc11354 10 Apr '02

10 Apr '02

I think I'm not linking the boost libary. But I checked many times and can't find any error. The test file I'm using is John Maddock's regex_split_example_1.cpp. I just renamed it to test.cpp, I also have a Makefile that look like this: *************************************************** CC = gcc MY_DIR = /home/dzhou/boost_1_27_0 MY_LIB = -L$(MY_DIR)/libs/regex/build/gcc MY_INCLUDE = -I$(MY_DIR) CFLAGS = -g -v -D_REENTRANT -Wall $(MY_INCLUDE) LIBS = $(MY_LIB)/libboost_regex.a LIBS_RPC = -lnsl RANLIB = ranlib RPCGEN_OPTS = -C .cc.o: $(CC) $(CFLAGS) -c $< PROGS = test all: ${PROGS} test: test.o ${CC} ${CFLAGS} -o test test.o ${LIBS} **************************************************** I've build the libary with make -f gcc.mak and it made the gcc dir I've tryed to play around with gcc.mak by changing g++ to gcc because I was getting errors with g++ also. #complier: CXX=gcc LINKER=gcc -shared here is the error that I'm getting: *********************************************************** gcc -g -v -D_REENTRANT -Wall -I/home/dzhou/boost_1_27_0 -c test.cc Reading specs from /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/specs gcc version 2.95.3 20010315 (release) /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/cpp0 -lang-c++ -v -I/home/dzhou/boost_1_27_0 -D__GNUC__=2 -D__GNUG__=2 -D__GNUC_MINOR__=95 -D__cplusplus -Dsparc -Dsun -Dunix -D__svr4__ -D__SVR4 -D__sparc__ -D__sun__ -D__unix__ -D__svr4__ -D__SVR4 -D__sparc -D__sun -D__unix -Asystem(unix) -Asystem(svr4) -D__EXCEPTIONS -g -Wall -D__GCC_NEW_VARARGS__ -Acpu(sparc) -Amachine(sparc) -D_REENTRANT test.cc /var/tmp/ccmuQP2y.ii GNU CPP version 2.95.3 20010315 (release) (sparc) #include "..." search starts here: #include <...> search starts here: /home/dzhou/boost_1_27_0 /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/../../../../include/g++-3 /usr/local/include /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/../../../../sparc-sun-solaris2.7/include /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/include /usr/include End of search list. The following default directories have been omitted from the search path: End of omitted list. /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/cc1plus /var/tmp/ccmuQP2y.ii -quiet -dumpbase test.cc -g -Wall -version -o /var/tmp/ccW67QRe.s GNU C++ version 2.95.3 20010315 (release) (sparc-sun-solaris2.7) compiled by GNU C version 2.95.2 19991024 (release). /usr/ccs/bin/as -V -Qy -s -o test.o /var/tmp/ccW67QRe.s /usr/ccs/bin/as: WorkShop Compilers 5.0 98/12/21 gcc -g -v -D_REENTRANT -Wall -I/home/dzhou/boost_1_27_0 -o test test.o -L/home/dzhou/boost_1_27_0/libs/regex/build/gcc/libboost_regex.a Reading specs from /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/specs gcc version 2.95.3 20010315 (release) /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/collect2 -V -Y P,/usr/ccs/lib:/usr/lib -Qy -o test /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/crt1.o /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/crti.o /usr/ccs/lib/values-Xa.o /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/crtbegin.o -L/home/dzhou/boost_1_27_0/libs/regex/build/gcc/libboost_regex.a -L/usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3 -L/usr/ccs/bin -L/usr/ccs/lib -L/usr/local/lib test.o -lgcc -lc -lgcc /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/crtend.o /usr/local/lib/gcc-lib/sparc-sun-solaris2.7/2.95.3/crtn.o ld: Software Generation Utilities - Solaris-ELF (4.0) Undefined first referenced symbol in file boost::bad_expression::~bad_expression(void)test.o boost::re_detail::c_traits_base::class_map test.o cout test.o string_char_traits<char>::assign(char &, char const &)test.o ostream::write(char const *, int) test.o string_char_traits<char>::compare(char const *, char const *, unsigned int)test.o boost::bad_pattern virtual table test.o __length_error(char const *) test.o boost::bad_expression virtual table test.o istream::ipfx1(void) test.o boost::c_regex_traits<char>::transform(basic_string<char, string_char_traits<char>, __default_alloc_template<false, 0> > &, basic_string<char, string_char_traits<char>, __default_alloc_template<false, 0> > const &)test.o ostream::operator<<(ostream &(*)(ostream &))test.o boost::c_regex_traits<char>::init(void)test.o endl(ostream &) test.o boost::re_detail::c_traits_base::lower_case_map test.o string_char_traits<char>::set(char *, char const &, unsigned int)test.o string_char_traits<char>::eos(void) test.o cerr test.o boost::bad_pattern::~bad_pattern(void)test.o boost::regbase::regbase(void) test.o ios::rdbuf(void) const test.o ostream::operator<<(char const *) test.o boost::re_detail::c_traits_base::syntax_map test.o runtime_error virtual table test.o boost::c_regex_traits<char>::transform_primary(basic_string<char, string_char_traits<char>, __default_alloc_template<false, 0> > &, basic_string<char, string_char_traits<char>, __default_alloc_template<false, 0> > const &)test.o boost::c_regex_traits<char>::toi(char)test.o ostream::operator<<(unsigned int) test.o string_char_traits<char>::copy(char *, char const *, unsigned int)test.o boost::re_detail::c_traits_base::do_lookup_class(char const *)test.o boost::c_regex_traits<char>::m_free(void)test.o boost::re_detail::c_traits_base::error_string(unsigned int)test.o streambuf::sbumpc(void) test.o boost::c_regex_traits<char>::update(void)test.o boost::re_detail::c_traits_base::do_lookup_collate(basic_string<char, string_char_traits<char>, __default_alloc_template<false, 0> > &, char const *)test.o cin test.o string_char_traits<char>::length(char const *)test.o istream::isfx(void) test.o boost::bad_expression::bad_expression(basic_string<char, string_char_traits<char>, __default_alloc_template<false, 0> > const &)test.o string_char_traits<char>::move(char *, char const *, unsigned int)test.o boost::c_regex_traits<char>::toi(char const *&, char const *, int)test.o ios::setstate(int) test.o __out_of_range(char const *) test.o ld: fatal: Symbol referencing errors. No output written to test collect2: ld returned 1 exit status *** Error code 1 make: Fatal error: Command failed for target `test' ********************************************************* Just a note, I don't have any errors when I test tokenizer ex: *************************************** #include <boost/regex.hpp> #include <iostream> #include <boost/tokenizer.hpp> int main(){ using namespace std; using namespace boost; string s = "Field 1,\"putting quotes around fields, allows commas\",Field 3"; tokenizer<escaped_list_separator<char> > tok(s); for(tokenizer<escaped_list_separator<char> >::iterator beg=tok.begin(); beg!=tok.end();++beg){ cout << *beg << "\n"; } } **************************************** however, it works with g++ only and not gcc. :/ - thank for any info. - David

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Re: [Boost-Users] Re: Newbie needs pointer to currently executing thread.
by dick.bridges＠tais.com 10 Apr '02

10 Apr '02

I'm implementing the Leader/Followers thread pool pattern - reference "Pattern-Oriented Software Architecture Volume 2" (Schmidt, et al). When a thread is released via notify_one(), it is [assumed to be] in the "leader" role and stores it's id. A sanity check should be performed to verify that there is no other thread in the leader role (i.e., current_leader is "none") before the thread stores it's id there. When one of the event sources is signaled and the leader is unblocked, it must, among other tasks, demote itself (i.e., set the current_leader value to "none") and promote one of the followers by notify_one() before continuing to service the request. Because of the potential for race conditions, (especially in the context of future program updates, modifications, etc.) I should enforce the rule that only the leader can promote a follower. Something along the lines of: current_leader == Thread::this(). "dmoore99atwork" <dmoore@ashtontec To: Boost-Users(a)yahoogroups.com hgroup.com> cc: Subject: [Boost-Users] Re: Newbie needs pointer to currently executing thread. 04/09/2002 06:53 PM Please respond to Boost-Users --- In Boost-Users@y..., dick.bridges@t... wrote: > Threads in a thread_group - derived pool are waiting on a condition. > Condition gets notify_one(). How do I get id/pointer for the thread that > was released? I've got a feeling I'm gonna be *REAL* embarrassed when I > find out, but I can't figure it out. > > Thanks for any help. Dick, In general, condition variables (both the Boost.Threads version and the POSIX version) don't tell the "notifier" which thread woke up. That's not necessarily a problem, though. A thread pool usually implies a set of threads that are equivalent in some way, even running the same thread function. Referring to the example at: http://www.boost.org/libs/thread/doc/condition.html#Example, Take a look the the receive() function. while (buffered == 0) buffer_not_empty.wait(lk); You might have three threads which reach this point when buffered==0 (meaning the buffer is empty). When a new sender in a fourth thread adds something to the buffer and calls notify_one(), exactly one of the three threads waiting on the condition will wake up and do some work. You won't care which thread wakes up, because any one of them will be prepared to do the necessary work. If this doesn't get you unstuck, please post more details, in particular why you feel it is important to know which thread "woke up" Regards, Dave 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 http://docs.yahoo.com/info/terms/

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Problem with File Dependency Example
by Martin Sander 10 Apr '02

10 Apr '02

Hi! (I'm a newbie to boost and English is not my native language) I changed the examples/file_dependencies.cpp from boost 1.0.27 a little bit and I think the output is wrong. The changed File is at http://www.ebx.de/qqq.cpp (just files_e, name and used_by are changed). The program printed "FF" and "GG" with the same time_slot, but they have an "Edge". With "#if 0" instead of "#if 1" on line 106 the result get even worse, "DD" has a lower time_slot than "GG", but "GG" depends on "DD". What is wrong? My code? Did I misuse the example? M.

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Cuthill Mckee Ordering Algorithm
by Sukandar, Erman H. 10 Apr '02

10 Apr '02

On the Graph documentation it is shown an example showing how to get reverse Cuthill-McKee ordering. It uses rbegin() to get it. My question is: how to get the non-reverse Cuthill-McKee ordering. It still give the reverse ordering even after I use begin(). Did I do something wrong? Can someone advise me the correct one (with example, if possible). Erman

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Detect derivation from e.g. addable
by whastingsnj 10 Apr '02

10 Apr '02

Is there a way to detect that a class has been derived from boost::addable<T>, for example? I would like to be able to write something like this: template <typename T> void foo() { //if T derived from boost::addable<T,...> // . . . } The problem, of course, is the base class chaining feature. I do not see how to use boost::is_base_and_derived in this case.

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Newbie needs pointer to currently executing thread.
by dick.bridges＠tais.com 10 Apr '02

10 Apr '02

Threads in a thread_group - derived pool are waiting on a condition. Condition gets notify_one(). How do I get id/pointer for the thread that was released? I've got a feeling I'm gonna be *REAL* embarrassed when I find out, but I can't figure it out. Thanks for any help.

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Where it is Boost.Signal?
by Raul Huertas Diaz 08 Apr '02

08 Apr '02

I kept reading about a library named Boost.Signal. I think that this library is about signal and slots. But I can't find it in Boost. Can someone tell me where it is, please? I look for it in the Files section and in the CVS repository but i can't find it. Thanks in advance. -- Raúl Huertas Díaz rhuertas at tcpsi dot es http://www.tcpsi.es

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Re: [Boost-Users] Building graphviz under VC6
by Wolf, Frank 08 Apr '02

08 Apr '02

Sorry for being inaccurate and thus wasting bandwidth. I meant the part under ...\libs\graph\src\ for the use of read_graphviz I really would be grateful for any help Thanks, Frank -----Ursprüngliche Nachricht----- Von: Jeff Garland [mailto:jeff@crystalclearsoftware.com] Gesendet: Mittwoch, 3. April 2002 17:49 An: Boost-Users(a)yahoogroups.com Betreff: RE: [Boost-Users] Building graphviz under VC6 Graphviz is not a boost library. This question would be more appropriate for graphviz-interest(a)research.att.com. Jeff > -----Original Message----- > From: Wolf, Frank [mailto:Wolf@bms.de] > Sent: Wednesday, April 03, 2002 1:56 AM > To: Boost-Users(a)yahoogroups.com > Subject: [Boost-Users] Building graphviz under VC6 > > > Has anyone succesfully build the graphviz libs under VC6? > I tried to do so, but ran into fatal error LNK1179 > > I really would be grateful for any help > Thanks. > Frank > 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 http://docs.yahoo.com/info/terms/

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