perf(frontend/compiler): support deser keyset using path

reduce memory usage by avoiding unecessary copy

compilers/concrete-compiler/compiler/lib/Bindings/Python/CompilerAPIModule.cpp

@@ -1433,6 +1433,26 @@ void mlir::concretelang::python::populateCompilerAPISubmodule(
             return std::make_unique<Keyset>(std::move(keyset));
           },
           "Deserialize a Keyset from bytes.", arg("bytes"))
+      .def_static(
+          "deserialize_from_file",
+          [](const std::string path) {
+            std::ifstream ifs;
+            ifs.open(path);
+            if (!ifs.good()) {
+              throw std::runtime_error("Failed to open keyset file " + path);
+            }
+
+            auto keysetProto = Message<concreteprotocol::Keyset>();
+            auto maybeError = keysetProto.readBinaryFromIstream(
+                ifs, mlir::concretelang::python::DESER_OPTIONS);
+            if (maybeError.has_failure()) {
+              throw std::runtime_error("Failed to deserialize keyset." +
+                                       maybeError.as_failure().error().mesg);
+            }
+            auto keyset = Keyset::fromProto(keysetProto);
+            return std::make_unique<Keyset>(std::move(keyset));
+          },
+          "Deserialize a Keyset from a file.", arg("path"))
       .def(
           "serialize",
           [](Keyset &keySet) {

frontends/concrete-python/concrete/fhe/compilation/keys.py

@@ -133,7 +133,7 @@ def load(self, location: Union[str, Path]):
             message = f"Unable to load keys from {location} because it doesn't exist"
             raise ValueError(message)
 
-        keys = Keys.deserialize(bytes(location.read_bytes()))
+        keys = Keys.deserialize(location)
 
         # pylint: disable=protected-access
         self._specs = None
@@ -185,20 +185,27 @@ def serialize(self) -> bytes:
         return serialized_keyset
 
     @staticmethod
-    def deserialize(serialized_keys: bytes) -> "Keys":
+    def deserialize(serialized_keys: Union[Path, bytes]) -> "Keys":
         """
-        Deserialize keys from bytes.
+        Deserialize keys from file or buffer.
+
+        Prefer using a Path instead of bytes in case of big Keys. It reduces memory usage.
 
         Args:
-            serialized_keys (bytes):
-                previously serialized keys
+            serialized_keys (Union[Path, bytes]):
+                previously serialized keys (either Path or buffer)
 
         Returns:
             Keys:
                 deserialized keys
         """
 
-        keyset = Keyset.deserialize(serialized_keys)
+        keyset = None
+        if isinstance(serialized_keys, Path):
+            keyset = Keyset.deserialize_from_file(str(serialized_keys))
+        elif isinstance(serialized_keys, bytes):
+            keyset = Keyset.deserialize(serialized_keys)
+        assert keyset is not None, "serialized_keys should be either Path or bytes"
 
         # pylint: disable=protected-access
         result = Keys(None)