Abf149/fix semi structured sparse (#16)

SUMMARY:
- Fix bug whereby 2:4 is not being invoked
- Eschew SparseTensor based implementation

TESTING:
- examples/offline_inference_semi_structured_sparse.py

---------

Co-authored-by: Lucas Wilkinson <[email protected]>

vllm/model_executor/layers/sparsity/sparse_w16a16_linear_method.py

@@ -6,7 +6,10 @@
 from vllm.model_executor.layers.linear import LinearMethodBase, set_weight_attrs
 from vllm.model_executor.layers.sparsity.base_config import SparsityConfig
 from vllm.model_executor.layers.parameters import LazyCompressedParameter
-from magic_wand import (CompressedStorageFormat, SparseBEGemmStorageFormat)
+from magic_wand.semi_structured import (pad_tensor_to_multiple,
+                                        extract_valid_rows)
+from magic_wand import (CompressedStorageFormat, SparseBEGemmStorageFormat,
+                        SparseSemiStructuredStorageFormat)
 from magic_wand.ops import be_ds_gemm
 
 
@@ -54,11 +57,18 @@ def apply_weights(
         if w.has_uncompressed_data:
             assert not w.has_compressed_data
             output = F.linear(x, w.uncompressed_data, bias)
-        # The current 2:4 implementation was running dense so ignore it
-        #  for now and instead just explicitly decompress as usual
-        # elif self.storage_format_cls == SparseSemiStructuredStorageFormat:
-        #     assert bias is None
-        #     raise NotImplementedError
+        elif self.storage_format_cls == SparseSemiStructuredStorageFormat:
+            assert bias is None
+            w_encap = w.compressed_data.encapsulated_torch_sparse_tensor
+            out_shape = (x.shape[:-1] + (w_encap.shape[0], ))
+            reshaped_x, valid_rows_range = pad_tensor_to_multiple(
+                x.reshape(-1, x.shape[-1]), 8)
+            output = F.linear(
+                reshaped_x, w_encap,
+                torch.nn.Parameter(torch.zeros((w_encap.shape[0], ))).to(
+                    reshaped_x.dtype).to(reshaped_x.device)).contiguous()
+            output = extract_valid_rows(output, valid_rows_range)
+            return output.reshape(out_shape)
         elif self.storage_format_cls == SparseBEGemmStorageFormat:
             assert bias is None
             assert w.compress_transposed