Building and Using Libraries CISC/QCSE 810

Libraries libraries exist for many common scientific tasks linear algebra – BLAS/ATLAS, LAPACK optimization – OPT++, TAO Fourier transforms – FFTW, FFTPACK image processing - Imagemagick data management – MySQL programming aids – Boost GUIs – Microsoft, Xwindows Tons more in C, or C++, or Java…

How you would use a library

Example: Imagemagick combination of library and executables contains routines for image processing

Obtaining the Source Libraries are binary files Not transferable from OS to OS Not necessarily optimized for a particular system Typical to need to recompile on most Unix-based Look for "source" or "tarball" ".tar.gz"

TAR files TAR (Tape ARchive) files are most common Unix-based way to pass around directories of source code Think "zip", but for unix Unix utility with staggering number of options

Common TAR scenarios Unpacking a gzipped tar file (.tar.gz) tar xvzf x – extract, v – verbose, z – gzipped, f – file to act on List files in a gzipped tar file tar tvf Create a tar file tar cvf mfile.tar

Imagemagick Located at Find the file ImageMagick.tar.gz Download it to your local drive move to a directory without spaces in Cygwin e.g. /cygdrive/c Untar tar xvzf ImageMagick.tar.gz

Read the Readme! There are standard steps many libraries use for building./configure make make test make install but that may not be the case for yours always look for installation instructions

This will take awhile… Configuring and compiling libraries can be a process of minutes to hours to overnight (hopefully not longer!) Have something else to do…

Assuming it worked If you successfully compiled and installed the library, you should now have header file(s) (.h) somewhere accessible a library file (.a) somewhere accessible Those extensions are for C, C++ libraries in Unix

Next Step: building a program You now want to try to link your own source files to the library Start with a worked example from the library writers! If that doesn't work, you know it's a configuration/linking problem

Imagemagick Comes with a thumbnail-generating program as a model Save as wand.c

Compiling against a library Look for –I flags in gcc command these add a search directory for "include" files your source will have to "#include " before you can use a library function ImageMagick 'make install' puts header files in /usr/include and subdirectories

Linking against a library Next step to is link the objects into an executable Look for flags -L: add a search directory for library files -l: adds a library to the executable  -lpng links code to libpng.a library file Most libraries found in /usr/lib or /usr/local/lib

Library Realities Building a library can be one of the most frustrating computer experiences you didn't write it whoever did may not have had your system at hand (or in mind) problems will tend to be at most esoteric level (compiler, OS, make, etc. behaving slightly differently than expected) Library writers are experienced C coders, while you may not be

Hope is not lost Google is your best friend search for the exact error message  someone else has probably had it search for your OS in the library's web site  most problems are often due to OS-specific issues Be patient a library could save you weeks to months of coding and testing; a few days to install isn't too much to ask

Your next task Find a library that might be of use to you (FFT, image processing, genetic algorithms, optimization), and build their example code OR Build some source code and link it into MATLAB (or Java)