problems in linking lapack to g77

[gradenig]

Hi,
it's nearly a weak i'm trying different commands to link my lapack libraries when i compile my fortran77 codes with g77.
Blas and Lapack libraries hava been installed and compiled automatically on my ubuntu linux release by a programm called 'Synaptic Package Manager'.
Searching on web i foud the command
g77 -o example.o example.f -L/usr/local/lib/ -llapack -lblas
Reading this i argued /usr/local/lib is the directory where lapack and blas shared library or symbolic links to shared libraries have been located; so i changed the path and i filled with /usr/lib/atlas, where i found files like liblapack.so.3. But nothing works!
When i try to compile a message appears saying:
/usr/bin/ld: cannot find -llapack
collect2: ld returned 1 exit status
So...can anyone help me?
Thank you very much, Giacomo

[Julie]

Giacomo,

First, you have to find out where exactly is your lapack library, and what is its name?

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locate liblapack

Usually, it is in /usr/local/lib and its name is liblapack.a or liblapack.so

Atlas is a blas optimised library. It provides the blas library optimised for your machine and a part of the lapack library (this is the one you have found),
But as you have installed Lapack, you should have the complete Lapack library somewhere else on your computer.

once you know the exact path to your Atlas and Lapack libraries :
- compile your program

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g77 -c example.f

- link your program to the lapack library and the atlas library with the correct path

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g77 -o example example.o $PATH_LAPACK/liblapack.a $PATH_ATLAS/libf77blas.a $PATH_ATLAS/libatlas.a

or for dynamic linking

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g77 -o example example.o $PATH_LAPACK/liblapack.so3 $PATH_ATLAS/libf77blas.a $PATH_ATLAS/libatlas.a

In fact the -L in the linking process scan the directory and search for libXXX.a if you put -lXXX. Another way to do it, is to directly put the complete path of the library in the linking command. (What I did).

If you really having trouble, you can download lapack from http://www.netlib.org/lapack and install it manually.
You can get documentation here: http://www.netlib.org/lapack/lawn81/node10.html


Julie

[gradenig]

Hi julie,
finally I could overcome the situation!
Your mail has been helpful to me to understand what was the exact object looked for by the command -l !
The path i gave to -L was right but no file was found by -l because all were named like liblapack.so.3 libblas.so.3 and none only liblapack.so or libblas.so.
In the end i had only to rename the binary files containig the shared libraries taking away the suffix .3 and everything worked!
thank you, giacomo.