Fix arch option in setup.py to work properly + not trigger on MSVC

.travis.yml

@@ -14,7 +14,7 @@ matrix:
       name: "Power PC"
       os: linux
       arch: ppc64le
-      if: type = cron
+      #if: type = cron
       before_install:
         - wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-ppc64le.sh -O miniconda.sh
         - mkdir $HOME/.conda
@@ -42,7 +42,7 @@ matrix:
       dist: focal
       virt: vm
       group: edge
-      if: type = cron
+      #if: type = cron
       before_install:
         - python -m pip install cython "numpy>=1.19.2" scipy
         - python -m pip install --no-build-isolation hypothesis matplotlib pytest pytest-cov pytest-xdist tqdm threadpoolctl

package/setup.cfg

@@ -7,7 +7,7 @@
 #use_cython=False
 #keep_cythonized=True
 ## enable cpu specific optimizations
-#march="native"
+march=native
 [wheel]
 universal = 1
 

package/setup.py

@@ -268,6 +268,13 @@ def using_clang():
     return is_clang
 
 
+def using_msvc():
+    """Will we be using an MSVC compiler?"""
+    # from numpy.random setup.py
+    is_msvc = (platform.platform().startswith('Windows') and
+               platform.python_compiler().startswith('MS'))
+    return is_msvc
+
 def extensions(config):
     # usually (except coming from release tarball) cython files must be generated
     use_cython = config.get('use_cython', default=cython_found)
@@ -280,12 +287,6 @@ def extensions(config):
         extra_compile_args.extend(['-Wall', '-pedantic'])
         define_macros.extend([('DEBUG', '1')])
 
-    # allow using architecture specific instructions. This allows people to
-    # build optimized versions of MDAnalysis.
-    arch = config.get('march', default=False)
-    if arch:
-        extra_compile_args.append('-march={}'.format(arch))
-
     # encore is sensitive to floating point accuracy, especially on non-x86
     # to avoid reducing optimisations on everything, we make a set of compile
     # args specific to encore see #2997 for an example of this.
@@ -295,6 +296,27 @@ def extensions(config):
     else:
         encore_compile_args.append('-O3')
 
+    # allow using architecture specific instructions. This allows people to
+    # build optimized versions of MDAnalysis. Do here so not included in encore
+    arch = config.get('march', default=False)
+    if arch:
+        if using_msvc():
+            # MSVC doesn't have a good equivalent for the march flag
+            pass
+        else:
+            if platform.machine() == 'x86_64':
+                extra_compile_args.append('-march={}'.format(arch))
+            elif platform.machine() == 'arm':
+                # arm prefers the use of  mcpu only
+                extra_compile_args.append('-mcpu={}'.format(arch))
+            elif platform.machine() == 'ppc64le':
+                # PowerPC prefers the use of mcpu and mtune
+                extra_compile_args.append('-mcpu={}'.format(arch))
+                extra_compile_args.append('-mtune={}'.format(arch))
+            else:
+                # platform specific optimizations skipped
+                pass
+
     cpp_extra_compile_args = [a for a in extra_compile_args if 'std' not in a]
     cpp_extra_compile_args.append('-std=c++11')
     cpp_extra_link_args=[]