Fix macOS gfortran installation (pyccel#1857)

Determine the location of the gfortran executable programatically.
This fixes a CI failure on macOS caused by a change in HomeBrew's
default installation directory. This solution should prevent a similar
problem arising again in the future. Fixes pyccel#1856.

**Additional changes**

- Increase tolerance on symbolic tests to avoid failures.
- Use isclose to compare floats instead of ==, which was causing
failures in a single unit test.

---------

Co-authored-by: Yaman Güçlü <[email protected]>

Author: EmilyBourne

.github/actions/macos_install/action.yml

@@ -7,9 +7,14 @@ runs:
       run: |
         brew install open-mpi
         brew install libomp
-        if [[ ! -f "/usr/local/bin/gfortran" ]]; then
-          gfort=$(ls /usr/local/bin/gfortran-* | tail -n 1)
-          ln -s ${gfort} /usr/local/bin/gfortran
+        GFORTRAN_HOME=$(which gfortran || true)
+        echo "GFORTRAN_HOME : $GFORTRAN_HOME"
+        if [[ ! -f "$GFORTRAN_HOME" ]]; then
+          gfort=$(find ${PATH//:/\/ } -name 'gfortran-*' -exec basename {} \; | sort | tail -n 1 || true)
+          echo "Found $gfort"
+          gfort_path=$(which ${gfort})
+          folder=$(dirname ${gfort_path})
+          ln -s ${gfort_path} ${folder}/gfortran
         fi
         echo "MPI_OPTS=--oversubscribe" >> $GITHUB_ENV
       shell: bash

tests/epyccel/test_epyccel_generators.py

@@ -120,7 +120,7 @@ def f(b : 'float[:]'):
 
     f_epyc = epyccel(f, language = language)
 
-    assert f(x) == f_epyc(x)
+    assert np.isclose(f(x), f_epyc(x), rtol=1e-14, atol=1e-14)
 
 @pytest.mark.parametrize( 'language', (
         pytest.param("fortran", marks = pytest.mark.fortran),

tests/symbolic/test_symbolic.py

@@ -14,8 +14,8 @@
 from pyccel.codegen.codegen import Codegen
 from pyccel.errors.errors   import Errors
 
-RTOL = 1e-12
-ATOL = 1e-16
+RTOL = 1e-13
+ATOL = 1e-14
 
 base_dir = os.path.dirname(os.path.realpath(__file__))
 path_dir = os.path.join(base_dir, 'scripts')