reduce shared library file size

setup.py

@@ -19,14 +19,15 @@ BUILD_DOCS = os.getenv('BUILD_DOCS', '0') == '1'
 def get_extensions():
     Extension = CppExtension
     define_macros = []
-    extra_compile_args = {'cxx': []}
+    extra_compile_args = {'cxx': ['-O2']}
+    extra_link_args = ['-s']
 
     if WITH_CUDA:
         Extension = CUDAExtension
         define_macros += [('WITH_CUDA', None)]
         nvcc_flags = os.getenv('NVCC_FLAGS', '')
         nvcc_flags = [] if nvcc_flags == '' else nvcc_flags.split(' ')
-        nvcc_flags += ['-arch=sm_35', '--expt-relaxed-constexpr']
+        nvcc_flags += ['-arch=sm_35', '--expt-relaxed-constexpr', '-O2']
         extra_compile_args['nvcc'] = nvcc_flags
 
     extensions_dir = osp.join(osp.dirname(osp.abspath(__file__)), 'csrc')
@@ -51,6 +52,7 @@ def get_extensions():
             include_dirs=[extensions_dir],
             define_macros=define_macros,
             extra_compile_args=extra_compile_args,
+            extra_link_args=extra_link_args,
         )
         extensions += [extension]