Don't require scipy for regular use

bitsandbytes/functional.py

@@ -233,8 +233,15 @@ def create_linear_map(signed=True, total_bits=8, add_zero=True):
         l = values.numel()//2
         return torch.Tensor(values[:l].tolist() + [0]*gap + values[l:].tolist())
 
+
 def create_normal_map(offset=0.9677083, use_extra_value=True):
-    from scipy.stats import norm
+    try:
+        from scipy.stats import norm
+    except ImportError as ie:
+        raise ImportError(
+            "Scipy is required for `create_normal_map`. "
+            "Install `bitsandbytes` with the `[test]` extra."
+        ) from ie
 
     if use_extra_value:
         # one more positive value, this is an asymmetric type

setup.py

@@ -26,7 +26,10 @@ def read(fname):
     license="MIT",
     keywords="gpu optimizers optimization 8-bit quantization compression",
     url="https://github.com/TimDettmers/bitsandbytes",
-    install_requires=['scipy'],
+    install_requires=[],
+    extras_require={
+        'test': ['scipy'],
+    },
     packages=find_packages(),
     package_data={"": libs},
     install_requires=['torch', 'numpy', 'scipy'],