Copy testInstallation.py to the simtk package and make it an import-safe module.

Also copy the test PDB file to the data/ directory, since we rather need it...

wrappers/python/simtk/testInstallation.py

+from __future__ import print_function
+import os
+import sys
+# First make sure OpenMM is installed.
+
+class TestingError(Exception):
+    """
+    An error is encountered when 
+    """
+
+def run_tests():
+    try:
+        from simtk.openmm.app import *
+        from simtk.openmm import *
+        from simtk.unit import *
+    except ImportError as err:
+        raise TestingError('Failed to import OpenMM packages; Make sure OpenMM\n'
+                           'is installed and the library path is set correctly.\n'
+                           'Error message: %s' % err.message)
+    
+    # Create a System for the tests.
+    data_dir = os.path.join(os.path.abspath(os.path.split(__file__)[0]), 'openmm', 'app', 'data')
+    pdb = PDBFile(os.path.join(data_dir, 'test.pdb'))
+    forcefield = ForceField('amber99sb.xml', 'tip3p.xml')
+    system = forcefield.createSystem(pdb.topology, nonbondedMethod=PME, nonbondedCutoff=1*nanometer, constraints=HBonds)
+    
+    # List all installed platforms and compute forces with each one.
+    
+    numPlatforms = Platform.getNumPlatforms()
+    print("There are", numPlatforms, "Platforms available:")
+    print()
+    forces = [None]*numPlatforms
+    platformErrors = {}
+    for i in range(numPlatforms):
+        platform = Platform.getPlatform(i)
+        print(i+1, platform.getName(), end=" ")
+        integrator = LangevinIntegrator(300*kelvin, 1/picosecond, 0.002*picoseconds)
+        try:
+            simulation = Simulation(pdb.topology, system, integrator, platform)
+            simulation.context.setPositions(pdb.positions)
+            forces[i] = simulation.context.getState(getForces=True).getForces()
+            del simulation
+            print("- Successfully computed forces")
+        except:
+            print("- Error computing forces with", platform.getName(), "platform")
+            platformErrors[platform.getName()] = sys.exc_info()[1]
+    
+    # Give details of any errors.
+    
+    for platform in platformErrors:
+        print()
+        print("%s platform error: %s" % (platform, platformErrors[platform]))
+    
+    # See how well the platforms agree.
+    
+    if numPlatforms > 1:
+        print()
+        print("Median difference in forces between platforms:")
+        print()
+        for i in range(numPlatforms):
+            for j in range(i):
+                if forces[i] is not None and forces[j] is not None:
+                    errors = []
+                    for f1, f2 in zip(forces[i], forces[j]):
+                        d = f1-f2
+                        error = sqrt((d[0]*d[0]+d[1]*d[1]+d[2]*d[2])/(f1[0]*f1[0]+f1[1]*f1[1]+f1[2]*f1[2]))
+                        errors.append(error)
+                    print("{} vs. {}: {:g}".format(Platform.getPlatform(j).getName(),
+                                                  Platform.getPlatform(i).getName(),
+                                                  sorted(errors)[len(errors)//2]))
+
+if __name__ == '__main__':
+
+    try:
+        run_tests()
+    except TestingError as err:
+        print('An error was encountered during testing:')
+        print(err)
+        sys.exit(1)
+    except BaseException as err:
+        print('An unexpected error was encountered during testing:')
+        print(err)
+        sys.exit(1)