Ubuntu 16.04下编译Armadillo C++库报错求助

Hey there! Let's work through this Armadillo compilation error together. Since your command cuts off at -lbl..., I'll assume you meant -lblas — let's dive into common fixes for this scenario:

1. Fix Your Compilation Command #

First, make sure you're using the complete, correctly ordered linker flags. Linkers process libraries in the order they're listed, so Armadillo should come after LAPACK/BLAS (or test both orders if one fails). Try this full command:

g++ example1.cpp -o example1 -O2 -llapack -lblas -larmadillo

Or the more standard order (sometimes works depending on your system):

g++ example1.cpp -o example1 -O2 -larmadillo -llapack -lblas

2. Verify Armadillo Detected LAPACK/BLAS During Installation #

Armadillo needs to find LAPACK and BLAS when you build it. To check:

• Go back to the directory where you ran cmake . for Armadillo.
• Open the CMakeCache.txt file and look for these lines:

  ARMA_USE_LAPACK:BOOL=ON
  ARMA_USE_BLAS:BOOL=ON
  

If either is set to OFF, Armadillo didn't detect the libraries. Reinstall LAPACK/BLAS first, then re-run Armadillo's setup:

sudo apt-get install --reinstall liblapack-dev libblas-dev
cd /path/to/armadillo-source
rm CMakeCache.txt
cmake .
make
sudo make install

3. Confirm Library Paths Exist #

Sometimes the linker can't find installed libraries. Run these checks:

# Check if LAPACK is in standard paths
ls /usr/lib/liblapack.so
# Check if BLAS is in standard paths
ls /usr/lib/libblas.so

If these return "No such file or directory", the libraries might be in /usr/local/lib — add that path to your compilation command with the -L flag:

g++ example1.cpp -o example1 -O2 -L/usr/local/lib -larmadillo -llapack -lblas

4. Test a Minimal Program to Rule Out Code Issues #

Create a tiny test file test_arma.cpp to confirm the library itself works:

#include <armadillo>
using namespace arma;

int main() {
  mat A = randu<mat>(4,4);
  mat B = inv(A);
  mat C = A * B;
  C.print("A*inv(A) =");
  return 0;
}

Compile it with the corrected command. If this runs without errors, the problem is in your original example1.cpp code, not the library setup.

5. Use CMake (Easier Alternative for Beginners) #

Since you already have CMake installed, let it handle linker flags automatically. Create a CMakeLists.txt in your project folder:

cmake_minimum_required(VERSION 3.10)
project(arma_example)

find_package(Armadillo REQUIRED)
include_directories(${ARMADILLO_INCLUDE_DIRS})

add_executable(example1 example1.cpp)
target_link_libraries(example1 ${ARMADILLO_LIBRARIES})

Then build with these commands:

mkdir build && cd build
cmake ..
make

This avoids manual flag hunting and ensures all dependencies are correctly linked.

内容的提问来源于stack exchange，提问作者Sai Chaithanya Adapa