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Re: [Boost-announce] Formal Review Tribool
by Haim Cohen 05 Jun '04

05 Jun '04

Hi, I am happy to contribute my review for the tribool library. I am a software engineer developing EDA (Electronic Design Automation) software, so I think I can contribute my 2 cents to the review of tribool, as I think EDA tools will benefit from this library. I did not compile the library. I have made a quick reading of this library, but an in-depth study of this problem domain before. First of all, my first comment is about the library's name, as well as the class name. In logic circuit simulation, there are 4 values : 0, 1, x ( which is tribool referred to as undetermine ), and z ( represents high impedance - or disconnection, and sometime referred to as "tri state" ). So, I think users will find it quite confusing when they see the 'tri' in the library's name. Since the library implements a logic value which has some value that is unknown, I would suggest 'unknown bool' or 'x bool'. Now to the interface. I think that a macro which enables renaming of the x value should not be supplied. This will make people's code less standard. Same as we all know what 'true' and 'false' mean, we should adopt a unique name for 'unknown yet quite determined logic value'. I think the default 'undetermine' name is not a good name. My suggestions : logic_x, x_value, x_logic, unknwon_bool . I also think the default tribool constructor should create a tribool object which is 'undetermine'. (Not false, as in the documentation) Besides the above, I think the interface of the class is good and succinct. Some point for thought : Users might want arrays of tribools, with all the support of bitwise operations. Is this should be a part of tribool as well ? I do not know. Now I will refer to the implementation. In real-life problems, programs might make a heavy usage of the tribool class for simulations of logic circuits. A logic circuit (at least the combinatoric part) is a DAG where nodes are logic gates, and directed archs are wires. This graph might be the result of a synthesis process, where a high level language for hardware description (e.g Verilog) is compiled into this DAG. Note : This is a very general and simple description of the process. Life are much more difficult. So, outputs will be calculated by performing lexicographic order of the DAG, and calculating from inputs to outputs. I am telling this, to convince that performance is *very* important here. With a quick look at the implementation code, I think that calculating the value using branches (if else) will not result with good performance. Calculations with true/false values only is fast - CPU vendors dedicate special hardware for this, so calculation can be made in one machine cycle. Even bitwise calculation (up to some word width) is done in one machine cycle. Compilers are making use of this, and (hopefully) compiles boolean and bitwise operators to the appropriate instruction. Unfortunately, I did not see any CPU which supports built in true/false/X arithmetic. And even if there are such CPUs available, we will not be able to use it, since boost libraries should be portable. So, it is very tempting to think - how can we implement efficient true/false/X arithmetic using the existing boolean arithmetic ? One tempting idea is to represent true/false/X with some integers, and use bitwise arithmetic to get the right results. It seems there are no such integer values. I think I even managed to proof this. Since there is already a library implementing 4 values logic (0,1,x,z) - which is SystemC - I took a quick look on how they do it with their 4-states logic data type called sc_logic. They use an approach which I think should be also used in tribool. It seems that they maintain lookup tables for each operation: AND, OR, NOT, XOR (!=) and XNOR (==). As the internal representation of tribool is enumerated type, we can use the integer value of this enumerated type to access the lookup tables (primitive 2D fixed-size and fixed-values arrays) and get the result of the calculation. This will be much faster since most CPUs has a special addressing mode for accessing arrays. So, I suggest to change implementation to use class-static fixed array to perform calculations. I know that the spirit of Boost is portability and not performance, but since what is suggested here is actually very similar to a primitive data type which might be heavily used in applications, I think it is important to consider performance as well. I hope this review would be found useful. Haim -- _____________________________________________________ Haim Cohen Software Engineer haim.cohen(a)analog.com / haimcohen2002(a)hotmail.com Analog Devices Israel (972) - 9 - 9715 406

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Re:RE: [boost] serialization request
by Robert Ramey 05 Jun '04

05 Jun '04

Jeff Garland wrote: > > Robert Ramey wrote: > > > > >Russell Balest wrote > > > > > >>Does someone know where in the code I can implement this easily. > > >>I just want to ignore the comments. > > >> > > >easy to accommodate. Just create a use the following in your > > >serialize > > >functions: > > > > > >Template<class Archive> > > >Void serialize(Archive, my_class & t){ > > > std::string comment; > > > ar & BOOST_NVP("comment", comment); > > > ar & BOOST_NVP("myclass_data", t);; > > >} > > > > > >In which case your XML output will look like: > > > > > >... > > ><comment></comment> > > ><myclass_data>..contents of t</myclass_data> ... > > > > > > > > > > > Good idea. I'll probably do that. > Another approach would be to preprocess your input files and strip the > added comments using XSLT, perl, or a simple regex program. That way you > don't have to modify the data structures under test. Someone might complain that my original method has 2 inconvenience features a) it requires modification to the serializations b) it includes the (null) comment string place holder in all the archives including the binary one. So another alternative would be to derive from the included xml_?archive classes included in the package and redefine the override for named-value pair so that it inserts/extracts  before or after every tag. This method has the following features: a) doesn't require any kluging up of class serializations b) has the advantage of automatically includes the  for all object instances c) has the disadvantage of automatically includes the  for all object instances d) doesn't add any overhead in other archives. If c) above is intolerable you would have the option of making your own wrapper similar to NVP - (NVT) that you would use in your serializations rather than NVP whenever you wanted a comment place holder. That's really a variation on my first suggestion. Take your pick and good luck Robert Ramey

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question about logging into CVS
by Robert Ramey 05 Jun '04

05 Jun '04

I'm trying to build/update the CVS development tree on my machine and I can't get in. Here is my command line and response. What magic am I missing here? It seemed I had this problem some time ago and it just went away after a time. This time I've tried a few times over the lat 24 hours with always the same result. Robert Ramey cvs -d :pserver:anonymous@cvs.boost.sourceforge.net:/cvsroot/boost login Logging in to :pserver:anonymous@cvs.boost.sourceforge.net:2401:/cvsroot/boost cvs [login aborted]: connect to cvs.boost.sourceforge.net:2401 failed: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

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Formal Review Tribool
by Thomas Witt 05 Jun '04

05 Jun '04

The review of Douglas Gregor's Tribool library begins now and runs through Saturday, May 29. Here is a short introduction to the library: The 3-state boolean library contains a single class, boost::logic::tribool, along with support functions and operator overloads that implement 3-state boolean logic. The tribool class acts like the built-in bool type, but for 3-state boolean logic. The three states are true, false, and indeterminate, where the first two states are equivalent to those of the C++ bool type and the last state represents an unknown boolean value (that may be true or false, we don't know). When reviewing the library, please remember to include: * What is your evaluation of the design? * What is your evaluation of the implementation? * What is your evaluation of the documentation? * What is your evaluation of the potential usefulness of the library? * Did you try to use the library? With what compiler? Did you have any problems? * How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? * Are you knowledgeable about the problem domain? And finally, every review should answer this question: * Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. The library is available in the Boost files area as tribool-20031026.tgz Thank you, Thomas Witt -- Thomas Witt witt(a)acm.org

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Re:[boost] Re: Re:A question on serialization library
by Robert Ramey 05 Jun '04

05 Jun '04

Virendra Verma wrote: > Library woundn't care but the user would. For example, how would user > delete or modify the object (pointed by pointer in the class) once > loaded since user has no way of knowing how the object was allocated? My > understanding is that the library creates and owns the object (using some > kind of class factory) when loading from input stream unless user keeps a > common allocator and somehow binds it to library's serializer. > > > If a class has a pointer to an object, how does class know that the > > > pointer was created by library or the class itself before > > > serialization? > > > It doesn't. Why would it need to? > > > Robert Ramey The guiding principle behind saving/loading pointers is that the loaded set of C++ structures is exactly equivalent to the original ones that were saved. So issues regarding pointer ownership don't change. That is, whatever ownership policy that was used when the pointer was saved will be the same one that can be used for the set of C++ structures recovered. The only problem would be where the there are pointers that are not included in the set of serialized data. As long as the serialized set is complete and self-contained there should be no problem. That is, there should be no pointers pointing into the serialized data that are themselves not serialized. Robert Ramey

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boost::ref implicit conversion operator overload problems
by Jonathan Graehl 05 Jun '04

05 Jun '04

If I pass a boost::ref to a template function that calls operator() with one argument, the conversion to T& isn't used to find matching functions. The problem seems to also exist for other overloaded operators. What should I do in this case? I thought the idea was for the ref to be transparent to the template code you pass it to. As a stopgap, I wrote template functions "deref" that must be applied at the calling site (these just cast using unwrap_reference). This code works, but if you remove the "deref", doesn't compile under GCC or visual c++: #include <boost/ref.hpp> #include <cassert> template <class T> inline typename boost::unwrap_reference<T>::type & deref(T& t) { return t; } template <class T> inline const typename boost::unwrap_reference<T>::type & deref(const T& t) { return t; } struct Setter { int i; void operator()(int j) { i=j; } Setter() : i(0) {} Setter(int j) : i(j) {} }; template <class F> void apply1(F f) { deref(f)(1); } int main() { Setter s; apply1(s); assert(s.i == 0); apply1(boost::ref(s)); assert(s.i == 1); }

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bug - function.hpp missing include guard - see sourceforge patch
by Nicolas Desjardins 05 Jun '04

05 Jun '04

Dear Boost Developers, I've submitted a patch to your sourceforge patch section - item # 966723. The patch is also attached to this mail. Summary: function.hpp missing include guard patch function.hpp does not have an #ifndef/#endif include guard. This patch adds #ifndef BOOST_FUNCTION_HPP at the top of the file and #endif at the bottom. Thanks, Nicolas Desjardins Software Developer Orthosoft Inc. *** function.hpp.original 2004-06-04 13:54:25.000000000 -0400 --- function.hpp 2004-06-04 13:53:54.000000000 -0400 *************** *** 10,15 **** --- 10,16 ---- // William Kempf, Jesse Jones and Karl Nelson were all very helpful in the // design of this library. + #ifndef BOOST_FUNCTION_HPP #include <boost/preprocessor/iterate.hpp> #include <boost/detail/workaround.hpp> *************** *** 62,64 **** --- 63,67 ---- # include BOOST_PP_ITERATE() # undef BOOST_PP_ITERATION_PARAMS_1 #endif + + #endif // BOOST_FUNCTION_HPP

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Re:[boost] serialization request
by Robert Ramey 05 Jun '04

05 Jun '04

Russell Balest wrote > My request is support for xml  in the serialization > xml archive. I believe it currently chokes if I add a comment in an xml > archive. > The application is for QA to compose test objects in xml and then > read them into applications with boost serialization. > It would be nice to annotate the test object 'templates' with comments > so QA can know what values are valid. > Does someone know where in the code I can implement this easily. > I just want to ignore the comments. Hmmm - my question is: What program is generating the XML archive in the first place? It its being generated by something other than the serialization library itself, its not going to be easy to generate such an archive that is guaranteed to be compatible with the C++ data structures of the reading program. (The organization of the data in the C++ program is what dicates the XML schema). At best it would be a maintenance pain in the neck to keep the reading program based on serialization in sync with some other program that doesn't use serialization to generate the XML archive. On the other hand, if the original XML archive is generated by the serialization library and just modified with comments, your request is very easy to accommodate. Just create a use the following in your serialize functions: Template<class Archive> Void serialize(Archive, my_class & t){ std::string comment; ar & BOOST_NVP("comment", comment); ar & BOOST_NVP("myclass_data", t);; } In which case your XML output will look like: ... <comment></comment> <myclass_data>..contents of t</myclass_data> ... After the archive is created you can edit the space between <comment> and </comment> with anything you want - it would be just thrown away. Generally I wouldn't encourage the practice of editing an archive but in this circumstance I could see it as an acceptable practice. But then this raises the question if the comments are so important, why are they being thrown them away? Shouldn't they be data read by the program? Robert Ramey

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Re: Boost Mathematicians
by Michael D. Crawford 05 Jun '04

05 Jun '04

I have a bachelor's degree in physics, with the intention to go back to school and get a PhD someday. One thing I've had in mind for quite some time is to improve the state of high-energy physics software. Maybe it's improved since I was last in school, but when I did my senior thesis in 1993 the software I worked with was an awful mess. At the time I became convinced that bogus results were being published in the peer-reviewed journals because of undetected software bugs. Mike -- Michael D. Crawford GoingWare Inc. - Expert Software Development and Consulting http://www.goingware.com crawford(a)goingware.com Tilting at Windmills for a Better Tomorrow. "I give you this one rule of conduct. Do what you will, but speak out always. Be shunned, be hated, be ridiculed, be scared, be in doubt, but don't be gagged." -- John J. Chapman, "Make a Bonfire of Your Reputations" http://www.goingware.com/reputation/

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Filesystem patch
by John Maddock 05 Jun '04

05 Jun '04

Beman, I'm committing a patch (below) for my last filesystem patch, basically I've found another reason why GetFileAttributes can fail when the file does not exist. John. $ cvs diff -u johnmaddock(a)cvs.sourceforge.net's password: cvs diff: Diffing . Index: operations_posix_windows.cpp =================================================================== RCS file: /cvsroot/boost/boost/libs/filesystem/src/operations_posix_windows.cpp, v retrieving revision 1.33 diff -u -r1.33 operations_posix_windows.cpp --- operations_posix_windows.cpp 30 Mar 2004 15:19:58 -0000 1.33 +++ operations_posix_windows.cpp 5 Jun 2004 11:47:23 -0000 @@ -321,10 +321,12 @@ # else if(::GetFileAttributesA( ph.string().c_str() ) == 0xFFFFFFFF) { - if((::GetLastError() == ERROR_FILE_NOT_FOUND) || (::GetLastError() == ERROR_PATH_NOT_FOUND)) + UINT err = ::GetLastError(); + if((err == ERROR_FILE_NOT_FOUND) || (err == ERROR_PATH_NOT_FOUND) || (err == ERROR_INVALID_NAME)) return false; // GetFileAttributes failed because the path does not exist // for any other error we assume the file does exist and fall through, // this may not be the best policy though... (JM 20040330) + return true; } return true; # endif

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