View source for Cross compile with LAPACK library on Nokia N9

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[toc align_right="yes" depth="3"]
[[Category:Developing_with_Qt::Harmattan]]
[[Category:Developing_with_Qt::Workarounds]]

= Cross compile a Qt program for Harmattan using the LAPACK library =

== Summary ==

[http://www.netlib.org/lapack/#_presentation LAPACK] provides routines for solving systems of simultaneous linear equations, least-squares solutions of linear systems of equations, eigenvalue problems, and singular value problems. It is written in Fortran 90.

It is not obvious how to link against LAPACK when cross-compiling a program for use on a Harmattan device as the 'official' method doesn't seem to work as expected.

Workarounds seem to be required both for obtaining the libraries and for cross-compiling the program. An interpretation of the 'official' method, and a workaround method, are included below. This method is based on the method by avieli [http://talk.maemo.org/showpost.php?p=1103831&amp;amp;postcount=9 here].

== Method 1: The 'Official' Method ==

Ideally the Nokia Qt Creator Harmattan SDK would come with LAPACK, BLAS and GFORTRAN libararies as standard. However, this does not appear to be the case. If it were you should then be able to add the following lines of code to your project file:

<code> CONFIG+=link_pkgconfig
 PKGCONFIG+=libblas
 PKGCONFIG+=liblapack
 PKGCONFIG+=libgfortran
</code>

QMake would then create a makefile and the libraries would be automatically linked when compilation took place.

At the moment the problems seem to be:

# These libraries are not in the standard Nokia Qt Creator SDK install (with Harmattan options selected) - they have to be downloaded and pkg-config files constructed manually;
# QMake does not seem to correctly construct the makefile with references to these libraries - it only references the directories where these libraries reside (i.e. my makefile did not include the '-l' statements which referenced the specific libraries.)

h2. Method 2: The 'Workaround' Method

This method is based on the method by avieli [http://talk.maemo.org/showpost.php?p=1103831&amp;amp;postcount=9 here].

h3. Step 1- Find the libraries and download them to your desktop

* Open the xterm on your Nokia N9 
* Type "devel-su" and password "rootme"
* Type "apt-get install libblas3gf", "apt-get install liblapack" and "apt-get install libgfortran"

Note: you can also download the LAPACK and BLAS (but not GFORTRAN?) libraries onto your desktop
http://harmattan-dev.nokia.com/pool/harmattan/free/l/lapack/
http://harmattan-dev.nokia.com/pool/harmattan/free/b/blas/

* Copy these files from /usr/lib on N9 to your "MyDocs" directory then onto your desktop

* Move the libraries to your Harmattan libraries area on your desktop (e.g. /opt/QtSDK/Madde/sysroots/harmattan_sysroot_10.2011.34-1_slim/lib)

=== Step 2: Create pkg-config files for each library ===

For each library create a ".pc" file to describe its location:

<code># Package Information for pkg-config

prefix=/opt/QtSDK/Madde/sysroots/harmattan_sysroot_10.2011.34-1_slim/
exec_prefix=${prefix}
libdir=${exec_prefix}/lib/
includedir=${prefix}/include/
Name: lapack
Description: LAPACK library
Version: Unknown
Libs: -L${libdir}
Cflags: -I${includedir}</code>

Save these files to the /usr/lib/pkgconfig directory in your Harmattan area (e.g. <code>/opt/QtSDK/Madde/sysroots/harmattan_sysroot_10.2011.34-1_slim/usr/lib/pkgconfig@)

h3. Step 3- Open your project file in Qt Creator

Add the links to the libraries to your ".pro" project file:

</code> CONFIG+=link_pkgconfig
 PKGCONFIG+=libblas
 PKGCONFIG+=liblapack
 PKGCONFIG+=libgfortran
<code>

=== Step 4 - Select 'Build'-'Run qmake' from within Qt Creator

h3. Step 5- Manually edit the Makefile it creates to include references to the LAPACK, BLAS and gfortran libraries ===

i.e. convert this:
</code>@LIBS = $(SUBLIBS) -L/opt/QtSDK/Madde/sysroots/harmattan_sysroot_10.2011.34-1_slim/usr/lib -L/usr/X11R6/lib -L/opt/QtSDK/Madde/sysroots/harmattan_sysroot_10.2011.34-1_slim/lib/lapack/ -L/usr/lib -lQtOpenGL -lQtGui -lQtCore -lGLESv2 -lpthread </code>
<code> to this:
</code>LIBS = $(SUBLIBS) -L/opt/QtSDK/Madde/sysroots/harmattan_sysroot_10.2011.34-1_slim/usr/lib -L/usr/X11R6/lib -L/opt/QtSDK/Madde/sysroots/harmattan_sysroot_10.2011.34-1_slim/lib/lapack/ -l:libblas.so -l:liblapack.so -l:libgfortran.so.3 -L/usr/lib -lQtOpenGL -lQtGui -lQtCore -lGLESv2 -lpthread
<code>

Click the 'Build' button to compile the program as you would usually. 

h3. Step 6- Run the program on your remote device

The BLAS, LAPACK and gfrotran libraries are already installed from the earlier step.