I need a C++ algebra library in order to use in my project. At the beginning I thought I can write one, but then I realized I was unsuccessfully trying to reinvent the wheel and wasting my precious time.
For arithmetic issues I found GMP Library (you know, for unlimited arithmetic calculations), and tools for other kind of tasks (standard C++ library seemed quite enough for pseudo-random number generation). However, I couldn't find a suitable one for algebraic works.
There are linear algebra libraries (such as Armadillo) but I'm not sure I need such a library. I want to summarize my needs.
#include <string>
#include <somelibrary.h>
int main(){
std::string str = "3*x^3+2*x^2+x+sqrt(x)*x^(1/3)";
algebraic_expression* exp = new algebraic_expression(str);
}
I want to have a tree from such an expression. Lets say it will return a std::vector or C style array with some information. For example (considering the example above) exp[0] will be "3*x^3", or maybe exp[0]["base"]="x".And why do I need this? Actually I can do the similar things by means of using RegEx, but sometimes I cannot handle it for example 3*x^0 is simply 3, I cannot print 3*x^0 because it is meaningless I want to have 3 (just like 3*x^1 is 3*x). Or (3-3)*5*2 will return 0, etc...
Thank you for your help.
You should look for 'CAS' (Computer Algebra System) . I can suggest you two:
Ginac http://www.ginac.de/
Giac: http://www-fourier.ujf-grenoble.fr/~parisse/giac.html
An example program with Giac: http://www-fourier.ujf-grenoble.fr/~parisse/giac_us.html#First%20example
Giac also comes with a GUI application called XCAS. It's a very powerful tool you should give it a try.
I've used LAPACK for my Master thesis program for 3D algebra calculations.
link : http://www.netlib.org/lapack/ link of c++ version of
library : http://www.netlib.org/lapack++/
Related
I am using the GNU scientific library and I was wondering what was the differences between those two function to copy a vector to another :
gsl_blas_dcopy and gsl_vector_memcpy
do you have any idea which one would be the fastest ?
In the GSL manual, section 8.3.6, it says
However, it is useful to have a small number of utility functions
which do not require the full blas code. The following functions fall
into this category.
int gsl_vector_memcpy
So both are basically the same. If you already need BLAS functionality, use gsl_blas_dcopy.
Rumors say a BLAS implementation for you specific CPU might be the fastest.
I have a simple question.
How can I make a program that can operate on huge float numbers without external libraries?
I got the idea to actually throw a whole library into my source code.
I found this: https://github.com/panks/BigInteger/blob/master/BigIntegerSingleFile.cpp
However when I'm dividing simple numbers like 20/12 it's always giving me "0".
So I decided to use GMP instead of BigInt but I have no idea how to include it in my code without using #include statement. My code needs to use only standard libraries.
I am a solo developer on a large C++ library that I use for research (I'm a PhD student). Let's say the library has a bunch of classes that implement cool algorithms: Algorithm1, Algorithm2, etc. I then write a bunch of C-style functions that are stand-alone "scripts" that use the library to either test the recently added functionality or to run simulations that produce plots that I then include in wonderfully-brilliant (I'm in denial) journal publications. The design of the library follows good software engineering principles (to the best of my knowledge and ability), but the "scripts" that link the library from main.cpp do not follow any principle except: "get the job done".
I now have over 300 such "scripts" in a single file (20,000+ lines of code). I have no problem with it, I remain very productive, and that's really the ultimate goal. But I wonder if this approach has major weaknesses that I just have learned to live with.
// File: main.cpp
#include <cool_library/algorithm1.h>
#include <cool_library/algorithm2.h>
...
#include <cool_library/algorithmn.h>
void script1() {
// do stuff that uses some of the cool library's algorithms and data structures
// but none of the other scriptX() functions
}
void script2() {
// do stuff that uses some of the included algorithms and data structures
}
...
// Main function where I comment in the *one* script I want to run.
int main() {
// script1();
// script2();
// script3();
...
script271();
return 0;
}
Edit 1: There are several goals that I have in this process:
Minimize the time it takes to start a new script function.
Make all old script functions available at my finger tips for search. So I can then copy and paste bits of those scripts into a new one. Remember this is NOT supposed to be good design for use by others.
I don't care about the compilation time of the script file because it compiles in under a second as it is now with the 20,000 lines of code.
I use Emacs as my "IDE" by the way, in Linux, using the Autoconf/Automake/Libtool process for building the library and the scripts.
Edit 2: Based on the suggestions, I'm starting to wonder if part of the way to increase productivity in this scenario is not to restructure the code, but to customize/extend the functionality of the IDE (Emacs in my case).
If I were you, I would split that huge file into 300 smaller ones: each would have just one scriptNN() and main() calling just it.
Now, when you have it compiled, you will have 300 small scriptNN executables (you may need to create appropriate Makefile for this though).
What's nice about this - now you can use these script executables as building blocks to be put or called by other scripts, like bash, python, perl, etc.
EDIT Explanation how this design allows to address your goals.
Time to start new script function - simply copy one of existing files and tweak it a little.
Make all old script functions available at my finger tips for search - emacs can do multi-file search across all other script files you have.
I don't care about the compilation time of the script file - it does not matter then. But you will have all of them available to you at once, without editing one big main() and recompiling.
Your example may be a good use case of scripting language. To be more specific, you could all your script* C++ functions glued to some interpreter, like Lua, Python, Ocaml, Guile etc... and have your test cases be written in the scripting language.
All scripting languages enable you to glue your C (hence also C++) functions.
For Lua, see its Lua API chapter. For Python, see its Extending & Embedding Python section. For Ocaml, see Interfacing C with OCaml section. For Guile, see Programming in C chapter.
You may wish to embed the interpreter inside your main function, or you could extend the existing interpreter with your new C++ functions (hence using some main provided by the interpreter).
Notice that using some scripting language may have a profound impact on the design and architecture of your library and software
If you are comfortable with it, and it works for you, just stick with it. You said you are the only developer, then just do whatever you want. I always spend too much time thinking about things like this for my projects :P. I've learned to just focus on the important and productive things. Theoretical things only work in theory...
All the suggested answers are good and you can even combine them. Just to add my 5 cents: your execution flow fits exactly into Strategy and Command design patterns. You may want to look at their benefits, but it's a question of benefit vs. investment.
I'm trying to adjust some mathematical code I've written to allow for arbitrary functions, but I only seem to be able to do so by pre-defining them at compile time, which seems clunky. I'm currently using function pointers, but as far as I can see the same problem would arise with functors. To provide a simplistic example, for forward-difference differentiation the code used is:
double xsquared(double x) {
return x*x;
}
double expx(double x) {
return exp(x);
}
double forward(double x, double h, double (*af)(double)) {
double answer = (af(x+h)-af(x))/h;
return answer;
}
Where either of the first two functions can be passed as the third argument. What I would like to do, however, is pass user input (in valid C++) rather than having to set up the functions beforehand. Any help would be greatly appreciated!
Historically the kind of functionality you're asking for has not been available in C++. The usual workaround is to embed an interpreter for a language other than C++ (Lua and Python for example are specifically designed for being integrated into C/C++ apps to allow scripting of them), or to create a new language specific to your application with your own parser, compiler, etc. However, that's changing.
Clang is a new open source compiler that's having its development by Apple that leverages LLVM. Clang is designed from the ground up to be usable not only as a compiler but also as a C++ library that you can embed into your applications. I haven't tried it myself, but you should be able to do what you want with Clang -- you'd link it as a library and ask it to compile code your users input into the application.
You might try checking out how the ClamAV team already did this, so that new virus definitions can be written in C.
As for other compilers, I know that GCC recently added support for plugins. It maybe possible to leverage that to bridge GCC and your app, but because GCC wasn't designed for being used as a library from the beginning it might be more difficult. I'm not aware of any other compilers that have a similar ability.
As C++ is a fully compiled language, you cannot really transform user input into code unless you write your own compiler or interpreter. But in this example, it can be possible to build a simple interpreter for a Domain Specific Language which would be mathematical formulae. All depends on what you want to do.
You could always take the user's input and run it through your compiler, then executing the resulting binary. This of course would have security risks as they could execute any arbitrary code.
Probably easier is to devise a minimalist language that lets users define simple functions, parsing them in C++ to execute the proper code.
The best solution is to use an embedded language like lua or python for this type of task. See e.g. Selecting An Embedded Language for suggestions.
You may use tiny C compiler as library (libtcc).
It allows you to compile arbitrary code in run-time and load it, but it is only works for C not C++.
Generally the only way is following:
Pass the code to compiler and create shared object or DLL
Load this Shared object or DLL
Use function from this shared object.
C++, unlike some other languages like Perl, isn't capable of doing runtime interpretation of itself.
Your only option here would be to allow the user to compile small shared libraries that could be dynamically-loaded by your application at runtime.
Well, there are two things you can do:
Take full advantage of boost/C++0x lambda's and to define functions at runtime.
If only mathematical formula's are needed, libraries like muParser are designed to turn a string into bytecode, which can be seen as defining a function at runtime.
While it seems like a blow off, there are a lot of people out there who have written equation parsers and interpreters for c++ and c, many commercial, many flawed, and all as different as faces in a crowd. One place to start is the college guys writing infix to postfix translators. Some of these systems use paranthetical grouping followed by putting the items on a stack like you would find in the old HP STL library. I spent 30 seconds and found this one:
http://www.speqmath.com/tutorials/expression_parser_cpp/index.html
possible search string:"gcc 'equation parser' infix to postfix"
I am working on an image processing project using Matlab. We should run our program (intended to be an application) on a cell phone.We were then asked to convert our code into C or C++ language so we get a feel of how long it would take for execution and then choose a platform. So far we didn't figure out how to do this conversion.. Any ideas of what to do to convert Matlab to C or C++??
The first thing you need to realise is that porting code from one language to another (especially languages as different as Matlab and C++) is generally non-trivial and time-consuming. You need to know both languages well, and you need to have similar facilities available in both. In the case of Matlab and C++, Matlab gives you a lot of stuff that you just won't have available in C++ without using libraries. So the first thing to do is identify which libraries you're going to need to use in C++. (You can write some of the stuff yourself, but you'll be there a long time if you write all of it yourself.)
If you're doing image processing, I highly recommend looking into something like ITK at http://www.itk.org -- I've written my image processing software twice in C++, once without ITK (coding everything myself) and once with, and the version that used ITK was finished faster, performed better and was ten times more fun to work on. FWIW.
Matlab can gererate C code for you.
See:
http://www.mathworks.com/products/featured/embeddedmatlab/
The generated code does however depend on matlab libraries. So you probably can't use it for a cell phone. But it might save you some time anyways.
I also used the MATLAB Coder to convert some functions consisting of a few hundred lines of MATLAB into C. This included using MATLAB's eigenvalue solver and matrix inversion functions.
Although Coder was able to produce C code (which theoretically was identical), it was very convoluted, bloated, impossible to decipher, and appeared to be extremely inefficient. It literally created about 10x as many lines of code as it should have needed. I ended up converting it all by hand so that I would actually be able to comprehend the C code later and make further changes/updates. This task however, can be very tedious/dangerous, as the array indexing in Matlab is 1-based and in C it's 0-based. You're likely to add bugs into the code, as I experienced. you'll also have to convert any vector/matrix arithmetic into loops that handle scalars (or use some type of C matrix algebra package)
The MathWorks provides a product called MATLAB Coder that claims to generate "readable and portable C and C++ code from MATLAB® code". I haven't tried it myself, so I can't comment on how well it accomplishes these goals.
With regard to the Image Processing Toolbox, this list (presumably for R2016b) shows which functions have been enabled for code generation and any limitations they may have.
Matlab has a tool called "Matlab Coder" which can convert your matlab file to C code or mex file. My code is relatively simple so it works fine. Speed up gain is about 10 times faster. This saves me time coding a few hundreds lines. Hope it's helpful for you too
Quick Start Guide for MATLAB Coder Confirmation
The links describe the process of converting your code in 3 major steps:
First you need to make a few simplifications in your present code so that it would be simple enough for the Coder to translate.
Second, you will use the tool to generate a mex file and test if everything is actually working.
Finally you would change some setting and generate the C code. In my case, the C code has about 700 lines including all the original matlab code (about 150 lines) as comments. I think it's quite readable and could be improve upon. However, I already get a 10 times speed up gain from the mex file anyway. So this is definitely a good thing.
We can't not be sure that this will work in all case but it's definitely worth trying.
I remember there is a tool to export m-files as c(++)-files. But I could never get that running. You need to add some obscure MATLAB-headers in the c/c++code, ... And I think it is also not recommended.
If you have running MATLAB-code, it shouldn't take too much effort to do the conversion "by hand". I have been working on several project where MATLAB was used and it was never consider to use any tools to convert the code to C/C++. It was always done "by hand".
I believe to have been the only one who ever investigate into using a tool.
Well there is not straight conversion from matlab to c/c++ You will need to understand the language and the differences between matlab and c/c++ and then start coding it in c/c++. Code a little test a little until it works.