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Yet more math functions - a draft TR2 proposal
by Paul A Bristow 12 Jul '04

12 Jul '04

I posted a note previous with modest reponse. In the hope that a better link will provoke some more reaction, I am reposting. As promised recently, I am presenting a draft of proposals for math functions which are needed for even most elementary statistics. I have been encouraged to submit this to both the C and C++ Standard Library groups at the same time. (They seem to speaking more than in the past). These are additions to the list drawn up by Walter Brown accepted into TR-1. The style and format follows his closely even though there were some opposition to them from the C++ community. However I think we have to accept that C and C++ compatibility are valued more than C++ 'ideality', and not try to re-open this area of dissent. The draft has been uploaded to the files area in a new folder Math Functions as "More Mathematical Functions.pdf" 220 kb. It is accessible at: http://tinyurl.com/357a6 be grateful if some CVS whizz would copy it to the sandbox as I know that many are unable to access the files section. It would be useful to have comments on 1 Typographical mistakes. 2 Mathematical mistakes (prepared by someone with seriously rusty math!). 3 The choice of functions espcially if there are any your feel strongly are missing, or are not needed (say why). 4 The choice of names. Clarity is preferred to curtness. 5 The choice of names for derivatives like the inverse and complement. I have added suffixes _inc and _c (or _com?). ( for C there will be suffixes f and l for the float and long double versions). Thanks. Paul Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB +44 1539 561830 +44 7714 330204 mailto: pbristow(a)hetp.u-net.com

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RE: [boost] Re: Boost.Threads: Do we need all those mutexes?
by Batov, Vladimir 11 Jul '04

11 Jul '04

What a wonderfully clean suggestion of having just one lock and (hopefully) just one mutex. IMHO having just one mutex class is even more important than having one lock as mutex represents something lockable that seems to always be the same. That is, I create a mutex and sometimes want to apply a blocking lock on it and sometimes I just want to try a lock. The functionality that implements various ways of locking is in locks. Although I can see the technical merits of having just one lock constructor, I still feel that having two explicit instead would be less ambiguous, friendlier towards the user and cleaner. Additionally, it'd keep the door open for possible optimization. Additionally, I'd expect the scoped_lock l(m, true) to be used much more often than scoped_lock l(m, false) Consequently, IMHO the first should get the preferential treatment. That is, to have an explicit and more efficient representation: scoped_lock::scoped_lock(Mutex&) Best, V. -----Original Message----- From: boost-bounces(a)lists.boost.org [mailto:boost-bounces@lists.boost.org] On Behalf Of Peter Dimov Sent: Sunday, 11 July 2004 10:47 PM To: boost(a)lists.boost.org Subject: Re: [boost] Re: Boost.Threads: Do we need all those mutexes? Michael Glassford wrote: > Peter Dimov wrote: >> After giving it some thought: >> >> - one lock class: tie; > > This seems both popular and reasonable. I presume it would be > templated on the mutex type? Seems entirely reasonable. Perhaps it's time to move to formal wording. template<class M> class scoped_lock { public: explicit scoped_lock( M & m, bool l = true ); // effects: if( l ) m.lock(); // post: locked() == l && mutex() == &m; ~scoped_lock(); // effects: if( locked() ) mutex()->unlock(); void lock(); // throws: lock_aready_locked if locked(); // effects: mutex()->lock(); // post: locked(); bool try_lock(); // throws: lock_aready_locked if locked(); // returns: mutex()->try_lock(); // post: locked() == (return value); bool timed_lock( xtime xt ); // throws: lock_aready_locked if locked(); // returns: mutex()->timed_lock( xt ); // post: locked() == (return value); void unlock(); // throws: lock_not_locked when !locked(); // effects: mutex()->unlock(); // post: !locked(); bool locked() const; Mutex * mutex() const; // returns: the associated mutex; operator unspecified-bool-type() const; // returns: locked(). }; I've added the mutex() accessor to support Andrei's lock idiom: void f() { scoped_lock lock( my_mutex ); f( lock ); } void f( scoped_lock & lock ) { // check for lock validity assert( lock.locked() && lock.mutex() == &my_mutex ); // proceed with operation } Now that we got rid of the excess locks, how about doing the same with the mutexes? class mutex // DefaultConstructible { private: void lock(); // pre: *this is not locked by the current thread // effects: blocks until *this is unlocked // post: *this is locked by the current thread bool try_lock(); // returns: true iff *this was unlocked // post: if *this was unlocked, *this is now locked by the current thread bool timed_lock( xtime xt ); // returns: true if *this is now locked by the current thread // effects: if *this is unlocked, returns immediately, otherwise blocks // until either *this is unlocked or xt has been reached // post: if *this was or became unlocked, *this is now locked by the // current thread void unlock(); // pre: *this is locked by the current thread // post: *this is unlocked }; The main potential issue here is mutex::timed_lock; try_lock doesn't seem controversial. It is true that Windows 95 does not have TryEnterCriticalSection, but an implementation can use Alexander Terekhov's alternative: http://lists.boost.org/MailArchives/boost/msg64648.php The mutex::timed_lock situation is a bit more complicated. POSIX labels pthread_mutex_timedlock as part of the Timeouts option, and I don't know whether this is because many implementations deliberatley do not provide timed locks, or because this is a relatively new addition to pthreads. Does someone know? My not-so-informed opinion at the moment is that we should provide timed_lock. I see that the current Boost.Threads implementation uses a mutex and a condition variable to implement a timed_lock-capable mutex, so we have a proof of concept that it can always be done, however there may be efficiency concerns. My line of thought is that since a mutex (usually) has a fast path user space portion and a slow path kernel space portion, with the timed_lock baggage not affecting the fast path, it seems reasonable to always require timed_lock (remember we're in "next standard mode" now, thinking severals years ahead). Thoughts? Some more random remarks regarding the state of Boost.Threads. Several files still seem to have incorrect line endings. This usually happens when checking in Windows line endings with a Unix CVS client. Please don't do that. I was somewhat surprised by the mutex/cv implementation. I expected a thin wrapper over pthreads, but this is not the case. At first sight it seems that the complexity is caused by the fact that boost::condition supports recursive mutexes that are locked more than once, whereas POSIX does not. I do not recall any discussions about this issue, and I'm not sure why this decision was made. It seems wrong (and the implementation seems buggy), but as usual, I may be missing something. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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Re: [boost] [optional] outdated tests?
by JOAQUIN LOPEZ MU?Z 11 Jul '04

11 Jul '04

----- Mensaje original ----- De: Rene Rivera <grafik.list(a)redshift-software.com> Fecha: Domingo, Julio 11, 2004 6:13 pm Asunto: [boost] [optional] outdated tests? > Boost.Optional optional_test and optional_test_ref both have the > following error: Cannot open include file: > 'boost/detail/none.hpp': No > such file or directory. > > But only on the Win32 tests, and not on the Linux test. Not sure > what > the discrepancy is about but the file is definitely not there in > CVS. Linux test also fail, but, as discussed in a previous thread, the reports pages are not getting updated due to a XML-related problem. I think Aleksey fixed that, so hopefully the pages will update again soon. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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Fw: STLport & boost
by François Dumont 11 Jul '04

11 Jul '04

Hello I am currently actively contributing to STLport. One of my contribution is to make boost and STLport closer. I think STLport can gain a lot in using some of the boost libraries and then boost will be able to count on a robust std lib. For the moment I only use 2 libraries from boost, type_traits and call_traits. I have some issue when I include the boost headers from STLport. I was counting on the BOOST_STD_CONFIG macro to limit the damage but for some platforms this feature is just useless. Under Win32 there is a workaround implemented for MSVC compilers (win32.hpp:60) on the min and max template functions. This workaround require the inclusion of the algorithm standard header which make the STLport lib build process failed. According the comment this workaround has not really been validated so my questions are: - is it require for all MSVC++ versions? Doesn't VC.Net 2003 or even 2002 managed the described cases correctly? - Couldn't this workaround be implemented for the native library only and not when using STLport? STLport looks to me as the right place to handle this case. Bests Francois Dumont

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Linux regressions
by John Maddock 11 Jul '04

11 Jul '04

There appear to be a few regressions in the Linux test results: 1) Several libraries are listed as failing with intel-linux-8 including config_test, regex, and python. However these do pass when tested on my own machine with the latest Intel binaries. Could this be a setup issue? For example if the compiler has recently been patched then you may need to clear out past builds before the tests will start passing again. 2) Test exec monitor is failing with gcc-2.96+STLPort which is causing quite a few other failures. 3) the test results look a little messed up somehow, and the failures listed in http://boost.sourceforge.net/regression-logs/cs-Linux.html don't match those in http://boost.sourceforge.net/regression-logs/cs-Linux/developer/. Definitely vacation time now... John.

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Re: [boost] Re: Pretty Good Initialization Library
by brangdon＠cix.compulink.co.uk 11 Jul '04

11 Jul '04

In-Reply-To: <cch4as$941$1(a)sea.gmane.org> andrewalex(a)hotmail.com (Andrei Alexandrescu $See Website for Email$) wrote (abridged): > I was worried more (only) about the order of evaluation. > > v += foo(), bar(); I don't think order of evaluation is sacred. However, I am also not keen on using comma for this. I'd rather use operator<<(). v << foo() << bar(); This is partly because comma is so small its easy to overlook, partly because it is used for so many other common things, and partly because I think the semantics of operator<<() fit better here. "Append these items to that stream or container, with conversion or formatting if appropriate." I would also be happy with: v << repeat(5) << 4; meaning: v << 4 << 4 << 4 << 4 << 4; and so forth. It doesn't bother me that: v = 1, 2, 3; has no direct equivalent. It becomes: v.clear(); v << 1 << 2 << 3; Presumably you'd be content with operator<<() in that it doesn't imply an order of evaluation. -- Dave Harris, Nottingham, UK

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boost::function code size
by Vladimir Prus 11 Jul '04

11 Jul '04

Hello, I've became interested in how efficient code-size-wise boost::function is, so I wrote a small script which generates a function which calls boost::function object N times and finds the size of the generated function. The results are somewhat interesting and somewhat alarming (to me). On gcc 3.3 with -Os, each call to boost::function costs 147 bytes of code size. With -O3 it's about 166 bytes. On gcc 3.4 calls cost 203 bytes with -Os and between 220 and 240 with -O3. However, when boost::function is called 15 times, the inliner heuristics kick in and calls are no longer inlined -- meaning each call costs about 14 bytes. This is a good thing for 3.4, but still: 1. For 3.3 boost::function causes a serious code bloat. 2. Even for 3.4, I'm not sure how it will perform if calls are done in several modules. Or how the heuristics will work on non-trivial cases: if they use the % of size increase then on large modules boost::function inlining can cost much more. Given that, IIUC, boost::function has to do indirect call somewhere anyway, I'm not sure inlining is such a good idea. Maybe some of the methods should be declared out-of-line, so that compiler don't try to inline them? - Volodya

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RE: [boost] Re: Boost.Threads: Do we need all those mutexes?
by Glen Knowles 10 Jul '04

10 Jul '04

> From: Howard Hinnant [mailto:hinnant@twcny.rr.com] > On Jul 9, 2004, at 11:00 PM, Glen Knowles wrote: > > >> <nod> I just implemented lock_both::lock two ways: Once > just keep > >> try-locking both ways, and once locking in the order of > the addresses > >> of the locks (with only two locks in the test, this was a safe > >> operator<). My test looks like: > > > > The problem case for spinning is when one thread gets the locks and > > the holds them for a non-trivial length of time. During > that time the > > other, spinning thread, just wastes cpu as fast as it can. > This just > > gets magnified as more threads are involved. > > You are describing a spin-lock, but not lock_both (except for > a theoretical and unlikely scenario). Yes, I didn't think it through all the way. Glen

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RE: [boost] Re: Re: Re: Pretty Good Initialization Library
by Glen Knowles 10 Jul '04

10 Jul '04

> From: Vladimir Prus [mailto:ghost@cs.msu.su] > > As Andras Erdei the gap between people who know about special > properties of operator(), and those who know that overloaded > version does not have that properties is very, very narrow. FWIW, I knew that a comma was a sequence point from experience with C but didn't know (never thought about) that it lost that property when overloaded in C++. Glen

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RE: [boost] Re: Boost.Threads: Do we need all those mutexes?
by Glen Knowles 10 Jul '04

10 Jul '04

> From: Matt Hurd [mailto:matt.hurd@gmail.com] > > Holding multiple locks is pretty common and necessary. If > you can guarantee they will always be acquired in the same > order they will not deadlock. It is necessary. :) > > AFAIK r/w locks only makes sense if you're going to hold read locks > > for a period of time, otherwise you're better off just > using a regular mutex. > > Concurrency may be better with shared access. > > The most common case for me is for collections. Multi-read > might be quite important to your application's concurrent performance. My logic is that using a read lock only improves concurrency over exclusion for that period of time that you hold the lock. If that period is short any improvement will likely be insignificant next to what you paid for hitting the memory barrier in either case. Of course, YMMV :) Glen

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