- Boost - lists.boost.org

[thread] thread member pointer & alert 2'nd attempt
by Roland Schwarz 14 Jan '05

14 Jan '05

A week ago I have tried to poll for interest of an extension to the threading library. 1) A thread member pointer 2) An alert mechanism Surprisingly (given the past discussions about related concepts) there have been almost no responses. So I am wondering whether this is because the possibly interested ones are still on vacation or the presented concept is deemed unusable. Also it might be the case that I have used the wrong buzzwords. Either way I would be glad to get your feedback on this. The files are in the vault: http://boost-sandbox.sourceforge.net/vault/index.php?action=downloadfile&di… Thank you for your attention. Roland

2 1

Re: Singleton
by Dave Handley 14 Jan '05

14 Jan '05

Jason Hise wrote: > > I'm actually working on the longevity policy now. I'm trying to do it > without using atexit, and instead using a hidden internal singleton that > manages the lifetimes of the others. It should be interesting. > Good idea - I look forward to seeing the results. > > 3) Possibly include the ability to turn off phoenix singletons in > > the dependency lifetime policy. > >From what I remember, Loki throws an exception. > This leads to an interesting question: what should happen if a class > tries to get access to a destroyed singleton? I would personally think > that it would always be desirable to have it come back, but then this is > just my opinion and probably falls into the same category as me > preferring dependencies to longevities. Which leads me to wonder if > OnDeadReference should be an additional policy of the lifetime policy > itself. Let me give you an example where you may want a dead reference exception rather than a phoenix singleton. Let's say you have a singleton that performs a client access to a database. When the client is started up, it asks for a username and password, and logs the client access in the database. You definitely would not want this to go through a phoenix singleton because of the side-affects. Making OnDeadReference a policy of the lifetime policy probably makes a lot of sense, since you have essentially implemented the phoenix singleton as an extra to the lifetime policy in the dependency model. > > > 4) Threading. > > I'm going to need help with this one. My current thought is to provide > a lock policy. The lock would be required to provide locking upon > creation and unlocking upon destruction, and then all the other policies > of the singleton would inherit this policy and could simply insert lock > objects wherever they are needed. The default single threaded lock > would just be an empty class. Unfortunately I have no experience with > how threading actually works, and I am worried that the two threads > would just end up creating two different locks and neither would block > the other. If I am not on the right track, please point me in the right > direction. > The problem with threading is that it is up to the OS to define the threading system. This means that threading is usually non-portable. I would recommend therefore looking at boost.threads which provides a portable threading system. Loki uses a very simple system of policies. The 3 policies implemented are a SingleThreadPolicy, ObjectLevelLocking and ClassLevelLocking. The object level locking basically locks a mutex that is defined on an object level, whereas the class level locks a mutex for all objects of that class. The implementation is via CRTP again. There are some added bits in Loki like the volatile type is typedefed so you can get the volatile qualifier right (you shouldn't use volatile in single-threaded because it can disable compiler optimisations). It does this using template <class Host> class ObjectLevelLocking { typedef volatile Host VolatileType; }; whereas the SingleThreaded version just does: typedef Host VolatileType; The locking itself works with an inner class called Lock that you construct on the stack whenever you need to lock. On construction it locks the mutex and on destruction it frees it. I've not personally used the boost threads library so I can't help you on that one. Dave Handley

10 17

Re: Singleton
by Dave Handley 14 Jan '05

14 Jan '05

Jason Hise wrote: > I have a question about the longevity lifetime. Does such a lifetime > only manage destruction order, or should it also manage order of > creation? The way I'm currently implementing my longevity lifetime > policy, there would be a master function in the > LongevityManagerSingleton which would set the 'creation level'. This > would basically create singletons up to this level or destroy them down > to this level, so that all singletons at a given level could be assured > that singletons with a smaller longevity number existed for their entire > lifetime. Example: > > A has longevity 0, B = 1, C = 2, D = 3, E = 4 > > Upon setting the creation level to 3, A would be created, then B, then > C, then D. Subsequently setting the creation level to 1 would destroy > D, then destroy C. > > Is this anything like what the users of a longevity lifetime would like, > or am I completely off track here? > I would have normally expected singleton creation to be handled with a lazy creation policy. This means that they are not created until used, and if not used never created. Then destruction would take place with the standard destruction policy. If you want to force creation at an earlier stage in the program execution then just call GetInstance() and throw away the result. BTW, regarding your concerns on integrating with say boost.thread, why not place all dependencies under a pre-processor guard, that enables threading. Then if you want to enable threading, you would set the pre-processor guard (like the smart pointers implementations), but also include the correct policy in your template specification. This means that under those circumstances where you want both threaded and un-threaded singletons, you can achieve this by turning on the boost directive, and using the policies accordingly. Without the pre-processor directive you simply would not have access to the multi-threaded policies. Dave

2 1

boost::polynomial
by Loïc Joly 14 Jan '05

14 Jan '05

Hello all boosters, I was wondering if a polynomial class has ever been proposed for boost ? Greetings, -- Loïc

2 1

saturated casts..
by Kristian Dupont 14 Jan '05

14 Jan '05

Forgive me if this topic has been discussed before - searching for "casts" and the like in the archives bring out quite a lot of results :) Although numeric_cast allows you to safely cast between numeric types, I find that it can sometimes come in handy to just receive the saturated value in the case of an overflow. A simplified solution would look something like this: template<class Source, class Target> inline Target saturated_cast(Source val) { BOOST_STATIC_ASSERT(std::numeric_limits<Target>::is_specialized); if(val < (std::numeric_limits<Target>::min)()) return (std::numeric_limits<Target>::min)(); if(val > (std::numeric_limits<Target>::max)()) return (std::numeric_limits<Target>::max)(); return static_cast<Target>(val); } I think that this would fit nicely into cast.hpp. Any comments? Kristian Dupont

3 4

Re: Re: [boost] Help me! Where is thefile"libboost_regex-vc6-mt-sgd-1_32.lib"?
by 袁晓辉 14 Jan '05

14 Jan '05

I asked: >>I am using Windows XP + VC6. My compiler complained about "LINK : fatal >>error LNK1104: cannot open file "libboost_regex-vc6-mt-sgd-1_32.lib" when >>using "Debug Multithreaded" run-time library! I alos got a similar error >>with "Multithreaded" run-time library, but OK with other types of run-time >>librares. John Maddock wort: >That is one of several regex lib variants that get build when you build >Boost, so it should be in your boost-install-path/lib directory. > >John. > I built boost libs like this: jam.exe -sBOOST_ROOT=. -sTOOLS=msvc "-sBUILD=debug release <runtime-link>static/dynamic Here are what I go: (I only tree "regex" directory for simplicity) tree G:\boost_1_32_0\bin\boost\libs\regex\ ...... ├─build │ ├─boost_regex.dll │ │ └─msvc │ │ ├─debug │ │ │ └─threading-multi(boost_regex-vc6-mt-gd-1_32.dll & boost_regex-vc6-mt-gd-1_32.lib) │ │ └─release │ │ └─threading-multi(boost_regex-vc6-mt-1_32.dll & boost_regex-vc6-mt-1_32.lib) │ └─libboost_regex.lib │ └─msvc │ ├─debug │ │ ├─runtime-link-static(libboost_regex-vc6-sgd-1_32.lib) │ │ └─threading-multi(libboost_regex-vc6-mt-gd-1_32.lib) │ └─release │ ├─runtime-link-static(libboost_regex-vc6-s-1_32.lib) │ └─threading-multi(libboost_regex-vc6-mt-1_32.lib) └─Release No "libboost_regex-vc6-mt-sgd-1_32.lib"! How can I build out this file?

2 1

program_options lib patch
by François Dumont 14 Jan '05

14 Jan '05

According some boost library sources I have checked it looks like there is an implicit coding standard rule which is to always use C functions from their C++ std namespace import equivalent. Thanks to this, compilers like MSVC6 but also Commeau according what I have read in comments, do not give compilation errors because of ambiguity. The program_options library do not apply this rule, here are the patch to fix it. It, of course, use the BOOST_NO_STDC_NAMESPACE to force std import when missing. In cmdline.cpp, this modification made the Commeau workaround irrelevant, it has been removed. Bests

3 5

graph lib patch
by François Dumont 14 Jan '05

14 Jan '05

isomorphism.cpp: Fix the use of the BOOST_NO_STDC_NAMESPACE subgraph.cpp: Change vector iterator i into it to avoid conflict with the i unsigned value defined later.

2 1

Boost Sandbox Files Registration...
by Rene Rivera 14 Jan '05

14 Jan '05

Just saw this from SF... ( 2005-01-13 10:12:24 - Project Web Service ) As of 2005-01-13 we have disabled the ability for project web content to send out e-mail. This action was taken to resolve a problem caused by spam generated from the project web services. We hope to restore this as soon as possible. So if you have problems registering for the Boost Sandbox Vault. Email me directly after doing the registration, and I'll activate the user manually. Hopefully SF can resolve the issue soon.. Or I can figure out a way around the problem. -- -- Grafik - Don't Assume Anything -- Redshift Software, Inc. - http://redshift-software.com -- rrivera/acm.org - grafik/redshift-software.com - 102708583/icq

1 0

Singleton
by Jason Hise 14 Jan '05

14 Jan '05

Yay, I finally got the singleton working with allocation and lifetime policies, in addition to being in CRTP form. I know that threading policies still remain, however I would like an opinion on what I have so far. A major difference from Loki is that my lifetime policy needs to know about the allocation policy in order for dependencies to be possible to implement. The code is available here: http://www.ezequal.com/chaos/libs/policy_singleton.h After I am assured that the structure of the code is pretty much correct, i will begin adding additional policies, such as the longevity lifetime that Loki supports. If there are policies that Loki doesn't provide that might be widely useful, please mention them so that they can be incorporated. I look forward to any and all feedback. -Jason

8 20