doc: add doc to use GPU for indexing (#611)

docs/src/ann_indexes.md

@@ -71,9 +71,41 @@ a single PQ code.
 ### Use GPU to build vector index
 
 Lance Python SDK has experimental GPU support for creating IVF index.
+Using GPU for index creation requires [PyTorch>2.0](https://pytorch.org/) being installed.
+
 You can specify the GPU device to train IVF partitions via
 
-- **accelerator**: Specify to `"cuda"`` to enable GPU training.
+- **accelerator**: Specify to ``cuda`` or ``mps`` (on Apple Silicon) to enable GPU training.
+
+=== "Linux"
+
+     <!-- skip-test -->
+     ``` { .python .copy }
+     # Create index using CUDA on Nvidia GPUs.
+     tbl.create_index(
+          num_partitions=256,
+          num_sub_vectors=96,
+          accelerator="cuda"
+     )
+     ```
+
+=== "Macos"
+
+     <!-- skip-test -->
+     ```python
+     # Create index using MPS on Apple Silicon.
+     tbl.create_index(
+          num_partitions=256,
+          num_sub_vectors=96,
+          accelerator="mps"
+     )
+     ```
+
+Trouble shootings:
+
+If you see ``AssertionError: Torch not compiled with CUDA enabled``, you need to [install
+PyTorch with CUDA support](https://pytorch.org/get-started/locally/).
+
 
 ## Querying an ANN Index
 

docs/test/md_testing.py

@@ -18,29 +18,45 @@ python_file = ".py"
 python_folder = "python"
 
 files = glob.glob(glob_string, recursive=True)
-excluded_files = [f for excluded_glob in excluded_globs for f in glob.glob(excluded_glob, recursive=True)]
+excluded_files = [
+    f
+    for excluded_glob in excluded_globs
+    for f in glob.glob(excluded_glob, recursive=True)
+]
+
 
 def yield_lines(lines: Iterator[str], prefix: str, suffix: str):
     in_code_block = False
     # Python code has strict indentation
     strip_length = 0
+    skip_test = False
     for line in lines:
+        if "skip-test" in line:
+            skip_test = True
         if line.strip().startswith(prefix + python_prefix):
             in_code_block = True
             strip_length = len(line) - len(line.lstrip())
         elif in_code_block and line.strip().startswith(suffix):
             in_code_block = False
-            yield "\n"
+            if not skip_test:
+                yield "\n"
+            skip_test = False
         elif in_code_block:
-            yield line[strip_length:]
+            if not skip_test:
+                yield line[strip_length:]
 
 for file in filter(lambda file: file not in excluded_files, files):
     with open(file, "r") as f:
         lines = list(yield_lines(iter(f), "```", "```"))
 
     if len(lines) > 0:
-        out_path = Path(python_folder) / Path(file).name.strip(".md") / (Path(file).name.strip(".md") + python_file)
+        print(lines)
+        out_path = (
+            Path(python_folder)
+            / Path(file).name.strip(".md")
+            / (Path(file).name.strip(".md") + python_file)
+        )
         print(out_path)
         out_path.parent.mkdir(exist_ok=True, parents=True)
         with open(out_path, "w") as out:
-            out.writelines(lines)
+            out.writelines(lines)