I want to use CORBA for a C application and thus I wanted to compare the various implementations available on the internet, e.g. the ones mentioned in the title. However, I can't find any comparison that is remotely up-to-date, like this and this.
My core requirements are as follows:
Client and server can be created in different languages and compiled on different OS's.
The server must be able to push calls.
No data overhead, i.e. Web Service with their relatively huge xml messages are out of question.
The CORBA implementation must be available under a free license that allows creation of commercial applications.
Can anyone here give advice? I know CORBA is old, as I have read
Why has CORBA lost popularity? and Is CORBA legacy?, so I don't want to start another discussion on how horribly bloated CORBA is etc. I'd just like to know which implementation fits my requirements the best, but if you know of something that's better than CORBA, feel free to post it here, too.
Cheers
Alex
I think the old comparisons are very old and not relevant any more. Of the three ORBs you mention TAO is actively maintained and supported, it is the leading ORB supporting the IDL to C++ language mapping.
TAO and MICO are both C++ ORBs, Orbit has support for C, so if your requirement is only pure C, than Orbit is the only option. If you can wrap again a C++ ORB in C, than TAO would be the option.
If you are looking for a more modern implementation, than check the new IDL to C++11 language mapping, which is very easy to use. There is one implementation already on the market, called TAOX11, which uses parts of TAO for its core, but that is a commercial ORB with developer licenses and royalty free runtime licenses.
Related
I'm looking to implement 'branch and bound' over a cluster (like Amazon's say), as I want it to be horizontally scalable, not limited to a single CPU. There's a paper "Task Pool Teams: A Hybrid Programming Environment for Irregular Algorithms on SMP Clusters" by Judith Hippold and Gudula Runger. It's basically a bottom-up, task-stealing framework like Intel's TBB, except for ad-hoc networks instead of shared memory. If this library was available I'd use it (replacing the local, threaded part with TBB). Unfortunately they don't seem to have made it available for download anywhere that I could find, so I wonder are there other implementations, or similar libraries out there?
It doesn't look like Microsoft's Task Parallel Library has the equivalent, either, to steal from.
(I tried to make a tag 'taskpool' after 'threadpool', the most-used variant (before 'thread-pool') but, didn't have enough points. Anyone heavy enough think it's worth adding?)
edit:
I haven't tried it yet, but it PEBBL (under here: software.sandia.gov/trac/acro/wiki/Packages) claims to scale really high. The paper that the answerer mentions from the Wiley book 'Parallel Branch-and-Bound Algorithms', Crainic, Le Cun and Roucairol, 2006, from "Parallel Combinatorial Optimization", 2006 edited by El-Ghazali Talbi was where I found it, and there are other libraries listed; some may be better, I reserve the right to update this :). Funny that Google didn't find these libs, either my Googling was weak or Google itself fails to be magic sometimes.
When you say "over a cluster" it sounds like you mean distributed memory, and parallelizing branch and bound is a notoriously difficult problem for distributed memory - at least in a way that guarantees scalability. The seminal paper on this topic is available here, and there's an excerpt from a Wiley book on the topic here.
Shared memory branch is bound is an easier problem because you can implement a global task queue. A good high level description of how to do both shared memory and message passing implementations is available here. If nothing else, the references section is worth purusing for ideas and existing implementations.
One thing you might consider is investigating shared message queues like RabbitMQ. It is a AMQP server (a messaging protocol developed so distributed applications can send messages to each other).
you basically need some kind of distributed synchronization/queue
I suggest looking into armci as a low-level distributed memory interface with synchronization and build on top of that.
Alternative is to allocate mpi process as Master to distribute work allocation.
http://www.cs.utk.edu/~dongarra/ccgsc2008/talks/Talk10-Lusk.pdf
Where can I find examples of code, written in "Unified Parallel C"?
I also interested in normative documents about this language (standards, reference manuals, online-accessible books and courses). What extensions were added to C to get UPC?
Is this dialect alive or dead?
UPC is still alive as a research project at UC Berkeley and is probably in use by high-performance computing facilities and national labs associated with the research group. You can get the latest version, released November 2009, here. Documentation, sample code, etc. can be found here. The language spec is here; there are many extensions on top of C99 syntax to support threads and inter-thread communication as first-class entities (perhaps not in the strictest sense of "first class", but certainly more so than in C, where you call out to opaque libraries to do synchronization and communication).
UPC is still in use some places; I am not an expert, but from what I can tell using UPC consists of a GCC-based compiler, a runtime, and a messaging layer GASNet that runs on top of your networking stack. These seem to be relatively well-supported on the types of machines for which you might want something like UPC. I wouldn't call it a huge developer community, but if you administer a large parallel machine, it's worth giving it a shot. If you just want something to work on your laptop, desktop, or server box, there is a wide variety of other parallel programming models with commercial support, tools, etc.
Other than the berkley UPC runtime based UPC implementations:
Berkley UPC-to-C translator http://upc.lbl.gov/download/source.shtml
and
gcc-upc http://www.gccupc.org)
there are also proprietary compilers by HP h30097.www3.hp.com/upc/
and Cray.
I believe that Cray and HP UPC versions both have progress guarentees, where as Berkley derived ones don't (This means that if you write spinlock style code, you have to explicitly call bupc_relax to prod teh runtime into precessing a remote write that would get you out of the loop)
UPC is still very much alive in the HPC community.
The new 1.3 version of the language/library specification was released in Nov 2013 and is available here:
https://upc-lang.org/upc-documentation
The major UPC compilers have already (or soon will) release 1.3 compliant versions.
The UPC specification is written as a "diff" against C99, so it's easy to see what's been added. At a high level it's linguistically a few new keywords and some extensions to the type system to accommodate the PGAS memory model and language-level SPMD threading. There is also a large (and growing) set of libraries for supporting common HPC needs in UPC applications.
There's lots more information on UPC at:
http://upc.lbl.gov/
where you can download a free, open source compiler that runs on vast variety of systems. The runtime source download includes a library of UPC example programs, benchmarks and test suites.
Once upon a time, a team of guys sat down and wrote an application in C, running on VMS on a VAX. It was a rather important undertaking and runs a reasonably important back-end operation at LargeCo. This whole shebang works so well that twenty-five years later it's still chugging along and doing it's thing.
Time passes and people retire and it so happens that the Last Man Standing has turned over the keys to a new generation who - we might imagine - are less than thrilled to find themselves caretakers of a system old enough to be their younger brother. Yet, as underwhelmed as they are by the idea of dealing with Ultra Legacy Systems, they can't justify the cost of replacing the venerable application.
LMS discovered that I habla unix and put this question to me. And since I habla unix but don't speak the C I shall summarize and put it to you. Long Story Short:
LMS wants to port LegacyApp, written in C. from VMS to unix. Resources? Any books he can read? People he can talk to?
The first question I'd need to ask is why, and I'd be leading the conversation in the direction of "Do you really need to port it off of VMS". There are a number of things worth mentioning about VMS:
-> VMS is still actively developed and maintained by HP. They just release V8.4 for Field Test last week (see http://h71000.www7.hp.com/openvmsft/).
-> VMS is available on new hardware; specifically HP's Integrity servers based on the Itanium processor.
-> VMS is also available on virtual platforms via the Charon Emulation products.
-> Popular estimates are that there are about 300,000 VMS systems still in active use today. LMS may be the last man at LargeCo, but he's far from the last man standing worldwide.
-> Lots of information out there, see openvms.org for example, to see lots of current information on VMS, all from current users.
OK - you still want to port off of VMS. How do you do it? Well, it depends on lots of stuff.
-> As others have said, how standard is the code? Chances are, not very. The more VMS-isms, the more difficult the job. 'nuff said.
-> What is the database? If it's Oracle, probably not too tough to move to Oracle on some other platform. If it's some sort of custom DB based on RMS index files, then you've got more work to do, you'll need to re-create that pseudo DB, or, understand it enough to replace it with some relational DB.
-> Besides C, what else is used to create the application? What's on the front end? DECforms? FMS? Is there a transaction engine, e.g. ACMS? RTR? These things will have a huge impact on the feasibility and effort required to port to UNIX.
-> What other products are involved? Are there any 3rd party libraries being used? Are there 3rd party products in use that are critical to the application or functionality?
-> Is this system clustered? If so why? You'll need to meet those same goals with the UNIX box.
-> There are companies out there that will help you do it, and claim to have tools to make it easier, but my experience is that these companies tend to be selling you more services than products (i.e. you need to hire them to use the tools. It'll be expensive).
The book UNIX for OpenVMS Users will give the VMS novice some help in understanding VMS, but, as the title says, the book is really intended for the opposite purpose.
Everything written on VMS uses lots of VMS specific stuff it was just so convenient.
There are a few companies that sell compatibility libs to make the port easier - they wont be cheap though, VMS tended to be used where reliability mattered more than cost.
The other option is to run openVMS on some modern hardware, possibly in a VM.
I am sure Brian has made his decision by now, but for my sins of working for many years in DEC OpenVMS language support (yes, some people had this dubious honour) the real question I would have asked a customer such as Brian is: is it a real-time application or not? If it is the former, then it would be heavily dependent on many VMS system services which would rule out a 'port' and indicate a re-write. If it were the latter then the frequency of VMS system services should (possibly) be limited and make a port viable.
The acid test for me, would be to SEARCH *.c "SYS$", "LIB$" i.e. to search all of the C source files for "SYS$" and "LIB$" tags which prefix VMS system services. If the count for these are in the 10s then a port is probably likely, between 10 and 100 makes it possibly likely, but over a 100 makes a successful port highly unlikely.
Hope this helps
You have several choices.
Get the OpenVMS source, and continue to maintain Open VMS as if it were a Linux distribution. Some folks don't mind keeping up with Linux distributions and OpenVMS distributions. It can be done.
Try to recompile the VMS C into Linux. This can be trivial if the C used only standard libraries. This can be very, very difficult if the C used a lot of VMS libraries.
Once you have facts at your fingertips, you can reevaluate this course of action. Since you didn't list a bunch of VMS library methods this program uses, it's impossible to tell how entangled it is with the OS.
This may be trivial or impossible. It's difficult to tell without analysis of the source.
Write bridge libraries from VMS to Linux. If your program only does a few VMS things, this isn't very difficult. If your program does extensive VMS things, this is craziness.
The bridge -- in the long run -- is a terrible idea. Managers love it, however.
An alternative is to replace the VMS library calls with proper, portable Linux calls rather than write bridges. This is better in the long run, because it excises the non-portable features of the program.
Rewrite it from scratch in Python. That is usually simpler than trying to port the C code. It will be shorter, cleaner, simpler, and portable.
If you're willing to keep running VMS in a VM, you can look into CHARON-VAX ( http://www.charon-vax.com/ ). As previously mentioned, the ease of porting really depends a lot on how much of the VMS extensions were used; searching the source code for $ characters embedded in strings (usually with a 3-character leading substring, such as lib$gettime or dsc$descriptor or sys$foobar etc) will give you at least a basic idea of what VMS system functions are called and how likely they are to be portable, if the name is reasonably obvious.
If it ain't broke, don't fix it! Why port it or migrate the app if you don't have to? Why not run it on a current install of OpenVMS running on an HP Itanium server; that is assuming you wish to upgrade the hardware, which may not even be necessary if your VAX hardware is still running strong.
To learn C, you might as well drag it from the horse's mouth: "The C Programming Language" by its inventors, Kernighan and Ritchie.
I can recommend "The UNIX programming environment" by (again) Brian Kernighan; a more authoritative source you'll hardly find, and it teaches you both Unix/C idioms and a bit of C programming at the same time.
For more depth and detail on C, I heartily enjoyed a book by Peter van der Linden: "Expert C Programming - Deep C Secrets".
You'll also want to wrestle LMS for a library documentation of VMS-specific C functions with (of course) special emphasis on those actually used in the app. That's where your porting effort will be.
The job could be easy or difficult, depending on how much machine-specific cleverness and bit-twiddling is done, and how many VMS-specific system calls are used. It would be very good if word size was equal (in other words, if your VMS box has a word size of 32 bits, don't run the code on a 64 bit version of Unix!)
Brian, I'm not sure if LMS specified/cared to port C-code or the WHOLE process. As too often people think of languages out of scope of systems.
If there're was a process built on VMS, most likely it used at least scheduling/batch facilities, which are often scripted in DCL (rather simple and clear language, unlike shell or perl scripting).
So the cost of porting the whole process may be higher than originally perceived by your LMS. Add here the reliability aspect, given your crunches with C, which is nothing impossible, of course, with enthusiasm and determination.
If you want simply give the C-code a try, as previously posted, search it for the "$" hits. Or just cc it with all headers present, the basics of compile-link command should be enough.
Alternatively, this looks like a consultant's call, as indeed such jobs were abundant at the "exodus" time. All said VMS remains quite a robust platform (24x7 is a norm!), unless the harware dies, then there're still tons of "exodus" spares. GOOD LUCK!
About a year and a half later, maybe you've already figured out what to do. My organization has recently decided to stick with OpenVMS instead of switching to Linux even though the old guard recently left. We just couldn't argue with what we felt was a very stable and reliable system. We are currently switching from Alpha servers to Integrity servers for end of life reasons. HP has been very helpful with our transition.
For that matter, there may be Linux vendors out there who can help with the transition. Ask your new hardware vendor if they have any recommendations.
Depending on what languages you already know, C is not that hard to learn. I taught myself C in the course of learning C++ after finally prying myself loose from Pascal.
(VAX Pascal, plus Rdb/VMS, plus DCL formed a combination that was hard to beat.)
If the software is typical C, you'll spend more time learning the library functions than learning the language.
It's pretty lightweight stuff, but I went through the online tutorials for C++ that Microsoft makes available in conjunction with the express edition of Visual Studio for C++.
Here's the beginner's tutorial:
http://msdn.microsoft.com/en-us/beginner/cc305129.aspx
It's probably worth making the effort to ask why LMS wants to port the application to Unix. The answer may seem obvious, but properly exploring the reasons has its benefits. I would assume:
OpenVMS is an "ultra legacy platform", and for that reason alone is something that is not worth running an application on anymore;
It's tough to find anyone who is willing to maintain an application that runs on OpenVMS these days;
The hardware on-which OpenVMS runs is threatening to become moribund.
We have a similar challenge, but in our case the application in question not only runs on OpenVMS but is also written in COBOL. I would have to say that your situation is rosy in comparison given that your application is written in a cross-platform language.
In any case, I think if you're about to make a big decision like moving from OpenVMS to Unix it would be prudent to do a little due diligence. In your case, try to assess just how portable the code is--only then will you know what the scale of the effort is (worst case could quite easily be a multiple of best case). In C, code portability is mostly a function of the dependencies--are they "standard" or are they VMS-specific?
Our enquiries revealed that HP would be supporting OpenVMS on Itanium until at least 2022. There isn't necessarily a need to rush to another platform--perhaps you could keep things on OpenVMS whilst embarking on an effort to prepare the application for porting (make it less dependent on OpenVMS specifics).
VMS has a surprisingly healthy community and if it's the lack of Unix that's the issue, then maybe GNV could help bridge the gap?
Well u have a few options. if this code needs to be ported rather quickly, i would write a bridge library to emulate the vms libs. whener you get it back up and running on a *nix, then go through replacing the vms library calls with native/portable calls for *nix.
Also if there is a lot of optimizations in the code ie inline assembly and bit twiddling. then you will have to rewrite thi code, which will take an understanding of the VAX arch. also. be sure to check word size differences and endian differences
I have heard of Boost and ACE as two of the well known C++ libraries. What are the other good C/C++ libraries available?
Does Boost and ACE support session management for web applications written in C/C++?
EDIT: Ok I will try to be domain specific. I am looking for a C/C++ library which could help me maintain session state for a C++ based CGI web application.
When you're trying to build a web application in C++ I'd recommend Wt, a Qt-like framework for creating web applications in C++.
It handles sessions either in one process per session (when security matters) or multiple sessions per process.
You can either use the built-in webserver or use it with any webserver that supports FastCGI.
(Also, I'd recommend it over Boost.CGI as it seems to be maintained and feature-complete).
Depends if you are talking about general purpose or domain specific libraries. For general purpose Boost is best of breed (and don't forget about the good old STL), so I don't see the point of looking for something else that will cover much of the same ground, but is not as polished. As for domain specific you'd have to specify the domain :-)
If you're interested in C (not C++) as well, glib (the Gnome project's utility library) provides a number of useful data structures and constructs.
C++ has libraries for anything you could imagine, so the scope of your question is rather undefined. What interests you? Web applications, scientific programs, GUIs? Specify what you need exactly if you want a good answer.
Boost is a general-purpose library for relatively low-level things. It's rather complex and advanced though, so you should have a good grasp of C++ before you start with it. ACE is mainly for synchronization and communication between threads/processes/applications.
If web applications is what you need, I recommend you to strongly consider the language you're picking. C++ may not be the best direction to go here, unless you have very specific constraints that force your hand.
There is also GTK which is good if you need to have a gui or use unicode. (although c++0x should have better unicode support natively when the standard is complete).
Boost doesn't yet support sessions, but a CGI library has been proposed which should have sessions.
If you want to use C++ for web applications, consider using CGICC
Ok I will try to be domain specific. I am looking for a C/C++ library which could help me maintain session state for a C++ based CGI web application.
CppCMS?
Example of session management: http://cppcms.sourceforge.net/wikipp/en/page/tut_sessions
Reference: http://cppcms.sourceforge.net/wikipp/en/page/ref_cppcms_session_iface
Configuration: http://cppcms.sourceforge.net/wikipp/en/page/ref_config#sessions
Poco is an excellent C++ Library with data access, xml, networking, compression and crypto all wrapped up in once nice little package.
Boost evidently, QT for GUI (that's not clearly a library I know), Electronic Arts Standard Template Library and
Blitz++ if you want to do scientific computation :
Blitz++ is a C++ class library for
scientific computing which provides
performance on par with Fortran 77/90.
The C++ programming language offers
many features useful for tackling
complex scientific computing problems:
inheritance, polymorphism, generic
programming, and operator overloading
are some of the most important.
Unfortunately, these advanced features
came with a hefty performance
pricetag: until recently, C++ lagged
behind Fortran's performance by
anywhere from 20% to a factor of ten.
As a result, the adoption of C++ for
scientific computing has been slow.
Is there a way to soup up C++ so that
we can keep the advanced language
features but ditch the poor
performance? This is the goal of the
Blitz++ project: to develop techniques
which will enable C++ to rival -- and
in some cases even exceed -- the speed
of Fortran for numerical computing,
while preserving an object-oriented
interface. The Blitz++ Numerical
Library is being constructed as a
testbed for these techniques.
Recent benchmarks show C++ encroaching
steadily on Fortran's high-performance
monopoly, and for some benchmarks, C++
is even faster than Fortran! These
results are being obtained not through
better optimizing compilers,
preprocessors, or language extensions,
but through the use of template
techniques. By using templates
cleverly, optimizations such as loop
fusion, unrolling, tiling, and
algorithm specialization can be
performed automatically at compile
time.
Another goal of Blitz++ is to extend
the conventional dense array model to
incorporate new and useful features.
Some examples of such extensions are
flexible storage formats, tensor
notation and index placeholders.
I don't ever recall coming across anything for C that's as extensive as C++'s Boost library.
You can have a look at glib. It provides quite a few interesting things like containers, unicode support, threading...
Have a look at its documentation
I've never seen anything. Really, C++ templates are the enabling technology for STL and much of boost, and C doesn't have them. I've seen many C-interface libraries for things like image processing, 3D graphics, networking, etc., but never a real general-purpose library like boost. You can find pieces though - threading libraries, string libraries, etc. - that are similar to sections of boost.
Depending on what exactly you're trying to do there is APR (The Apache Portable Runtime library) which is what the Apache http daemon is built on
http://apr.apache.org/
For GUI, there is wxWidgets (formerly wxWindows)
http://www.wxwidgets.org/
Glib does compensate it partially in form of various unicode, string types. If you add Gobject you could get some object programming even some garbage collection.
ACE (Adaptive Communication Environment) is sometimes mentioned. It's not quite an apples-to-apples comparison. Boost provides more "basic building blocks" whereas ACE provides more of an tightly integrated framework geared towards telco products. I have used both extensively and I find Boost vastly superior. One big advantage of Boost is that many of its features will show up in the STL extensions for the upcoming C++0x standard (see, for example, http://en.wikipedia.org/wiki/Technical_Report_1).
or you can look at ccan http://ccan.ozlabs.org/
but no, there really isn't any complete package, glib comes closest