Add FlatTensorDataMap to low-level pybindings

Summary:
Create pybindings around the FlatTensorDataMap::load function

This allows us to use the low-level program data separation APIs in pybindings, through program/method as well as Module.

Use `py::capsule` to capture the type `const NamedDataMap*` that is passed into method_load.

Example usage:
```
 >>> inputs = (torch.randn(3),)
 >>> program = _load_program_from_buffer(program_buffer)
 >>> data_map = _load_flat_tensor_data_map("model.ptd")
 >>> method = program.load_method("forward", data_map.get_named_data_map())
 >>> outputs = method(inputs)[0]
```

Differential Revision: D87461455

Author: lucylq

extension/pybindings/portable_lib.py

@@ -59,6 +59,8 @@
     _get_registered_backend_names,  # noqa: F401
     _is_available,  # noqa: F401
     _load_bundled_program_from_buffer,  # noqa: F401
+    _load_flat_tensor_data_map,  # noqa: F401
+    _load_flat_tensor_data_map_from_buffer,  # noqa: F401
     _load_for_executorch,  # noqa: F401
     _load_for_executorch_from_buffer,  # noqa: F401
     _load_for_executorch_from_bundled_program,  # noqa: F401
@@ -70,6 +72,7 @@
     ExecuTorchMethod,  # noqa: F401
     ExecuTorchModule,  # noqa: F401
     ExecuTorchProgram,  # noqa: F401
+    FlatTensorDataMap,  # noqa: F401
     MethodMeta,  # noqa: F401
     Verification,  # noqa: F401
 )

extension/pybindings/pybindings.cpp

@@ -21,6 +21,7 @@
 #include <executorch/devtools/etdump/etdump_flatcc.h>
 #include <executorch/extension/data_loader/buffer_data_loader.h>
 #include <executorch/extension/data_loader/mmap_data_loader.h>
+#include <executorch/extension/flat_tensor/flat_tensor_data_map.h>
 #include <executorch/extension/memory_allocator/malloc_memory_allocator.h>
 #include <executorch/extension/module/bundled_module.h>
 #include <executorch/extension/module/module.h>
@@ -82,6 +83,7 @@ using ::executorch::ET_RUNTIME_NAMESPACE::Kernel;
 using ::executorch::ET_RUNTIME_NAMESPACE::Method;
 using ::executorch::ET_RUNTIME_NAMESPACE::Program;
 using ::executorch::extension::BufferDataLoader;
+using ::executorch::extension::FlatTensorDataMap;
 using ::executorch::extension::MallocMemoryAllocator;
 using ::executorch::extension::MmapDataLoader;
 using ::executorch::extension::ET_BUNDLED_MODULE_NAMESPACE::BundledModule;
@@ -294,15 +296,17 @@ struct PyBundledModule : public BundledModule {
       uint32_t bundled_input_pool_size)
       : BundledModule(buffer.cast<std::string_view>().data()),
         bundled_program_ptr_(buffer),
-        program_ptr_(static_cast<const void*>(
+        program_ptr_(
+            static_cast<const void*>(
+                bundled_program_flatbuffer::GetBundledProgram(
+                    get_bundled_program_ptr())
+                    ->program()
+                    ->data())),
+        program_len_(
             bundled_program_flatbuffer::GetBundledProgram(
                 get_bundled_program_ptr())
                 ->program()
-                ->data())),
-        program_len_(bundled_program_flatbuffer::GetBundledProgram(
-                         get_bundled_program_ptr())
-                         ->program()
-                         ->size()) {}
+                ->size()) {}
 
   static std::unique_ptr<PyBundledModule> load_from_buffer(
       const py::bytes& buffer,
@@ -1367,9 +1371,21 @@ struct PyProgram final {
     return std::string(res.get());
   }
 
-  std::unique_ptr<PyMethod> load_method(const std::string& method_name) {
+  std::unique_ptr<PyMethod> load_method(
+      const std::string& method_name,
+      py::object named_data_map_obj = py::none()) {
+    const NamedDataMap* named_data_map = nullptr;
+    if (!named_data_map_obj.is_none()) {
+      // Extract pointer from py::capsule.
+      py::capsule named_data_map_capsule =
+          named_data_map_obj.cast<py::capsule>();
+      named_data_map = named_data_map_capsule.get_pointer<const NamedDataMap>();
+    }
     Result<Method> res = state_->program_->load_method(
-        method_name.c_str(), memory_->mem_manager(), event_tracer_.get());
+        method_name.c_str(),
+        memory_->mem_manager(),
+        event_tracer_.get(),
+        named_data_map);
     THROW_IF_ERROR(
         res.error(),
         "Failed to load method %s, error: 0x:%" PRIx32,
@@ -1470,6 +1486,40 @@ py::bool_ is_available(const std::string& backend_name) {
   return backend->is_available();
 }
 
+struct PyFlatTensorDataMap final {
+  explicit PyFlatTensorDataMap(
+      std::unique_ptr<DataLoader> loader,
+      FlatTensorDataMap data_map)
+      : loader_(std::move(loader)), data_map_(std::move(data_map)) {}
+  static std::unique_ptr<PyFlatTensorDataMap> load_from_file(
+      const std::string& path) {
+    auto loader = loader_from_file(path);
+    auto result = FlatTensorDataMap::load(loader.get());
+    THROW_IF_ERROR(result.error(), "Failed to load FlatTensorDataMap");
+    return std::make_unique<PyFlatTensorDataMap>(
+        std::move(loader), std::move(result.get()));
+  }
+  static std::unique_ptr<PyFlatTensorDataMap> load_from_buffer(
+      const py::bytes& buffer) {
+    auto loader = loader_from_buffer(
+        buffer.cast<std::string_view>().data(), py::len(buffer));
+    auto result = FlatTensorDataMap::load(loader.get());
+    THROW_IF_ERROR(result.error(), "Failed to load FlatTensorDataMap");
+    return std::make_unique<PyFlatTensorDataMap>(
+        std::move(loader), std::move(result.get()));
+  }
+
+  // Get a pointer to the underlying NamedDataMap as a py::capsule.
+  // The PyFlatTensorDataMap must outlive this pointer.
+  py::capsule get_named_data_map() {
+    return py::capsule(&data_map_, "NamedDataMap");
+  }
+
+ private:
+  std::unique_ptr<DataLoader> loader_; // Keep DataLoader alive.
+  FlatTensorDataMap data_map_;
+};
+
 } // namespace
 
 PYBIND11_MODULE(EXECUTORCH_PYTHON_MODULE_NAME, m) {
@@ -1670,6 +1720,7 @@ PYBIND11_MODULE(EXECUTORCH_PYTHON_MODULE_NAME, m) {
           "load_method",
           &PyProgram::load_method,
           py::arg("method_name"),
+          py::arg("named_data_map") = py::none(),
           call_guard)
       .def(
           "method_meta",
@@ -1721,6 +1772,22 @@ PYBIND11_MODULE(EXECUTORCH_PYTHON_MODULE_NAME, m) {
           py::arg("name"),
           call_guard)
       .def("method_meta", &PyMethod::method_meta, call_guard);
+
+  m.def(
+      "_load_flat_tensor_data_map",
+      &PyFlatTensorDataMap::load_from_file,
+      py::arg("data_path"),
+      call_guard);
+  m.def(
+      "_load_flat_tensor_data_map_from_buffer",
+      &PyFlatTensorDataMap::load_from_buffer,
+      py::arg("data_buffer"),
+      call_guard);
+  py::class_<PyFlatTensorDataMap>(m, "FlatTensorDataMap")
+      .def(
+          "get_named_data_map",
+          &PyFlatTensorDataMap::get_named_data_map,
+          call_guard);
 }
 
 namespace {

extension/pybindings/pybindings.pyi

@@ -288,3 +288,60 @@ def _unsafe_reset_threadpool(num_threads: int) -> None:
         This API is experimental and subject to change without notice.
     """
     ...
+
+@experimental("This API is experimental and subject to change without notice.")
+class FlatTensorDataMap:
+    """FlatTensorDataMap loads external data from a .ptd file.
+
+    .. warning::
+
+        This API is experimental and subject to change without notice.
+    """
+
+    def get_named_data_map(self) -> Any:
+        """Get a pointer to the underlying NamedDataMap.
+
+        Returns:
+            A capsule containing a pointer to the internal NamedDataMap
+            that can be passed to ExecuTorchProgram.load_method().
+
+        Warning:
+            The FlatTensorDataMap instance must outlive the returned capsule.
+        """
+        ...
+
+@experimental("This API is experimental and subject to change without notice.")
+def _load_flat_tensor_data_map(
+    data_path: str,
+) -> FlatTensorDataMap:
+    """Load a flat tensor data map from a file.
+
+    .. warning::
+
+        This API is experimental and subject to change without notice.
+
+    Args:
+        data_path: Path to the .ptd file with external data.
+
+    Returns:
+        A FlatTensorDataMap instance that can be used with ExecuTorchProgram.load_method().
+    """
+    ...
+
+@experimental("This API is experimental and subject to change without notice.")
+def _load_flat_tensor_data_map_from_buffer(
+    data_buffer: bytes,
+) -> FlatTensorDataMap:
+    """Load a flat tensor data map from a buffer.
+
+    .. warning::
+
+        This API is experimental and subject to change without notice.
+
+    Args:
+        data_buffer: Buffer holding a .ptd file with external data.
+
+    Returns:
+        A FlatTensorDataMap instance that can be used with ExecuTorchProgram.load_method().
+    """
+    ...

extension/pybindings/test/test_pybindings.py

@@ -733,3 +733,49 @@ def test_program_data_separation(self) -> None:
         )
         with self.assertRaises(RuntimeError):
             executorch_module_bundled_no_data.forward(inputs)
+
+    def test_flat_tensor_data_map(self) -> None:
+        eager_module = ModuleLinear()
+        inputs = eager_module.get_inputs()
+        expected = eager_module(inputs[0])
+        exported_program = export(eager_module, inputs, strict=True)
+        exec_program = to_edge(exported_program).to_executorch(
+            config=ExecutorchBackendConfig(
+                # Move all tensor data to '_default_external_constant' file.
+                external_constants=True,
+            )
+        )
+        program_buffer = exec_program.buffer
+        assert len(exec_program._tensor_data) == 1
+        data_buffer = bytes(exec_program._tensor_data.pop("_default_external_constant"))
+
+        # Test 1: Load FlatTensorDataMap from buffer.
+        program_from_buffer = self.load_prog_fn(program_buffer)
+        data_map_from_buffer = self.runtime._load_flat_tensor_data_map_from_buffer(
+            data_buffer
+        )
+        method = program_from_buffer.load_method(
+            "forward", data_map_from_buffer.get_named_data_map()
+        )
+        executorch_output = method(inputs)[0]
+        self.assertTrue(torch.allclose(expected, executorch_output))
+
+        # Test 2: Load FlatTensorDataMap from file.
+        import os
+        import tempfile
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pte_file = os.path.join(tmpdir, "linear.pte")
+            with open(pte_file, "wb") as f:
+                f.write(program_buffer)
+            ptd_file = os.path.join(tmpdir, "linear.ptd")
+            with open(ptd_file, "wb") as ptd:
+                ptd.write(data_buffer)
+
+            program_from_file = self.runtime._load_program(pte_file)
+            data_map_from_file = self.runtime._load_flat_tensor_data_map(ptd_file)
+            method_1 = program_from_file.load_method(
+                "forward", data_map_from_file.get_named_data_map()
+            )
+            executorch_output1 = method_1(inputs)[0]
+            self.assertTrue(torch.allclose(expected, executorch_output1))

shim_et/xplat/executorch/extension/pybindings/pybindings.bzl

@@ -8,35 +8,37 @@ MODELS_ATEN_OPS_LEAN_MODE_GENERATED_LIB = [
 ]
 
 PORTABLE_MODULE_DEPS = [
-    "//executorch/runtime/kernel:operator_registry",
-    "//executorch/runtime/executor:program",
     "//executorch/devtools/bundled_program/schema:bundled_program_schema_fbs",
-    "//executorch/extension/aten_util:aten_bridge",
     "//executorch/devtools/bundled_program:runtime",
+    "//executorch/devtools/etdump:etdump_flatcc",
+    "//executorch/extension/aten_util:aten_bridge",
     "//executorch/extension/data_loader:buffer_data_loader",
     "//executorch/extension/data_loader:mmap_data_loader",
+    "//executorch/extension/flat_tensor:flat_tensor_data_map",
     "//executorch/extension/memory_allocator:malloc_memory_allocator",
     "//executorch/extension/module:bundled_module",
     "//executorch/extension/module:module",
     "//executorch/extension/tensor:tensor",
+    "//executorch/runtime/executor:program",
     "//executorch/runtime/executor/test:test_backend_compiler_lib",
-    "//executorch/devtools/etdump:etdump_flatcc",
+    "//executorch/runtime/kernel:operator_registry",
 ] + get_all_cpu_backend_targets()
 
 ATEN_MODULE_DEPS = [
-    "//executorch/runtime/kernel:operator_registry_aten",
-    "//executorch/runtime/executor:program_aten",
     "//executorch/runtime/core/exec_aten:lib_aten",
     "//executorch/devtools/bundled_program/schema:bundled_program_schema_fbs",
+    "//executorch/devtools/bundled_program:runtime_aten",
+    "//executorch/devtools/etdump:etdump_flatcc",
     "//executorch/extension/data_loader:buffer_data_loader",
     "//executorch/extension/data_loader:mmap_data_loader",
+    "//executorch/extension/flat_tensor:flat_tensor_data_map_aten",
     "//executorch/extension/memory_allocator:malloc_memory_allocator",
     "//executorch/extension/module:bundled_module_aten",
     "//executorch/extension/module:module_aten",
     "//executorch/extension/tensor:tensor_aten",
-    "//executorch/devtools/bundled_program:runtime_aten",
     "//executorch/runtime/executor/test:test_backend_compiler_lib_aten",
-    "//executorch/devtools/etdump:etdump_flatcc",
+    "//executorch/runtime/executor:program_aten",
+    "//executorch/runtime/kernel:operator_registry_aten",
 ]
 
 # Generated lib for all ATen ops with aten kernel used by models in model inventory