[CMake] FORTRAN and BLAS Issue

[Tim Gallagher]

You're not using the results of the find_package. 

It should look like: 

cmake_minimum_required(VERSION 2.8) 
project(collision) 
enable_language(Fortran) 
FIND_PACKAGE(BLAS REQUIRED) 
add_definitions(-O3) 
add_executable(collision test.f90) 
target_link_libraries(collision ${BLAS_LIBRARIES}) 

Also, the add_definitions shouldn't really be used for things like -O3, it should be used for things like -DMY_FLAG or something. Flags like -O3 should be added to the CMAKE_Fortran_FLAGS. 

Tim 

----- Original Message -----

From: "Matthew Clay" <mpclay at gmail.com> 
To: cmake at cmake.org 
Sent: Thursday, May 3, 2012 11:25:23 PM 
Subject: [CMake] FORTRAN and BLAS Issue 

Fellow cmake users: 

I am experiencing a minor issue with cmake, and can't seem to find an answer browsing the web. I have a minimal working example that highlights the issue with my main code. The problem is this: compiling by myself with gfortran and the appropriate flags produces no errors, while attempting to build the code with cmake throws an error. 

The FORTRAN code--note that DDOT is the call to BLAS that I want to make: 

PROGRAM TEST 
IMPLICIT NONE 
DOUBLE PRECISION,DIMENSION(2) :: x,y ! The two vectors. 
REAL(KIND=8),EXTERNAL :: DDOT ! Their dot product. 
x(:) = (/ 1.,100. /) 
y(:) = (/ 1.,1. /) 
WRITE (*,*) DDOT(2,x,1,y,1) 
END PROGRAM TEST 

What works: 

gfortran test.f90 -O3 -lblas 
./a.out 

What doesn't work: 

cmake_minimum_required(VERSION 2.8) 
project(collision) 
enable_language(Fortran) 
FIND_PACKAGE(BLAS REQUIRED) 
add_definitions(-O3 -lblas) 
add_executable(collision test.f90) 

Upon attempting [ mkdir build && cd build && cmake .. && make ] as with any other code I get the following result: 

Scanning dependencies of target collision 
[100%] Building Fortran object CMakeFiles/collision.dir/test.f90.o 
Linking Fortran executable collision 
CMakeFiles/collision.dir/test.f90.o: In function `MAIN__': 
test.f90:(.text+0x7d): undefined reference to `ddot_' 
collect2: error: ld returned 1 exit status 
make[2]: *** [collision] Error 1 
make[1]: *** [CMakeFiles/collision.dir/all] Error 2 

It appears that BLAS is not being linked with the code...maybe? I am not a cmake expert, and would greatly appreciate any words of wisdom for troubleshooting this problem! 

Thanks, 
Matt 

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