move cuda_setup code into subpackage

bitsandbytes/__init__.py

@@ -12,6 +12,7 @@ from .autograd._functions import (
 )
 from .cextension import COMPILED_WITH_CUDA
 from .nn import modules
+from . import cuda_setup
 
 if COMPILED_WITH_CUDA:
     from .optim import adam

bitsandbytes/cextension.py

@@ -2,7 +2,7 @@ import ctypes as ct
 import os
 from warnings import warn
 
-from bitsandbytes.cuda_setup import evaluate_cuda_setup
+from bitsandbytes.cuda_setup.main import evaluate_cuda_setup
 
 
 class CUDALibrary_Singleton(object):

bitsandbytes/cuda_setup/compute_capability.py

@@ -0,0 +1,65 @@
+import ctypes
+from dataclasses import dataclass, field
+
+
+CUDA_SUCCESS = 0
+
+@dataclass
+class CudaLibVals:
+    # code bits taken from 
+    # https://gist.github.com/f0k/63a664160d016a491b2cbea15913d549
+
+    nGpus = ctypes.c_int()
+    cc_major = ctypes.c_int()
+    cc_minor = ctypes.c_int()
+    device = ctypes.c_int()
+    error_str = ctypes.c_char_p()
+    cuda: ctypes.CDLL = field(init=False, repr=False)
+    ccs: List[str, ...] = field(init=False)
+
+    def load_cuda_lib(self):
+        """
+        1. find libcuda.so library (GPU driver) (/usr/lib)
+           init_device -> init variables -> call function by reference
+        """
+        libnames = ("libcuda.so")
+        for libname in libnames:
+            try:
+                self.cuda = ctypes.CDLL(libname)
+            except OSError:
+                continue
+            else:
+                break
+        else:
+            raise OSError("could not load any of: " + " ".join(libnames))
+
+    def check_cuda_result(self, result_val):
+        """
+        2. call extern C function to determine CC 
+           (see https://docs.nvidia.com/cuda/cuda-driver-api/group__CUDA__DEVICE__DEPRECATED.html)
+        """
+        cls_fields: Tuple[Field, ...] = fields(self.__class__)
+
+        if result_val != 0:
+            self.cuda.cuGetErrorString(result_val, ctypes.byref(self.error_str))
+            print("Count not initialize CUDA - failure!")
+            raise Exception("CUDA exception!")
+        return result_val
+
+    def __post_init__(self):
+        self.load_cuda_lib()
+        self.check_cuda_result(self.cuda.cuInit(0))
+        self.check_cuda_result(self.cuda, self.cuda.cuDeviceGetCount(ctypes.byref(self.nGpus)))
+        tmp_ccs = []
+        for gpu_index in range(self.nGpus.value):
+            check_cuda_result(
+                self.cuda, self.cuda.cuDeviceGet(ctypes.byref(self.device), gpu_index)
+            )
+            check_cuda_result(
+                self.cuda,
+                self.cuda.cuDeviceComputeCapability(
+                    ctypes.byref(self.cc_major), ctypes.byref(self.cc_minor), self.device
+                ),
+            )
+            tmp_ccs.append(f"{self.cc_major.value}.{self.cc_minor.value}")
+        self.ccs = sorted(tmp_ccs, reverse=True)

bitsandbytes/cuda_setup/main.py

@@ -1,6 +1,6 @@
 """
 extract factors the build is dependent on:
-[X] compute capability  
+[X] compute capability
     [ ] TODO: Q - What if we have multiple GPUs of different makes?
 - CUDA version
 - Software:
@@ -23,7 +23,7 @@ import os
 from pathlib import Path
 from typing import Set, Union
 
-from .utils import print_err, warn_of_missing_prerequisite, execute_and_return
+from ..utils import print_err, warn_of_missing_prerequisite, execute_and_return
 
 
 def check_cuda_result(cuda, result_val):