feat: made encoding and decodings hashable

src/qiboml/models/decoding.py

@@ -4,7 +4,7 @@
 from qibo import Circuit, gates
 from qibo.backends import Backend, _check_backend
 from qibo.config import raise_error
-from qibo.hamiltonians import Hamiltonian
+from qibo.hamiltonians import Hamiltonian, Z
 
 from qiboml import ndarray
 
@@ -13,14 +13,15 @@
 class QuantumDecoding:
 
     nqubits: int
-    qubits: list[int] = None
+    qubits: tuple[int] = None
     nshots: int = None
     backend: Backend = None
     _circuit: Circuit = None
 
     def __post_init__(self):
-        if self.qubits is None:
-            self.qubits = list(range(self.nqubits))
+        self.qubits = (
+            tuple(range(self.nqubits)) if self.qubits is None else tuple(self.qubits)
+        )
         self._circuit = Circuit(self.nqubits)
         self.backend = _check_backend(self.backend)
         self._circuit.add(gates.M(*self.qubits))
@@ -47,8 +48,10 @@ def analytic(self):
             return True
         return False
 
+    def __hash__(self) -> int:
+        return hash((self.qubits, self.nshots, self.backend))
+
 
-@dataclass
 class Probabilities(QuantumDecoding):
     # TODO: collapse on ExpectationDecoding if not analytic
 
@@ -71,10 +74,7 @@ class Expectation(QuantumDecoding):
 
     def __post_init__(self):
         if self.observable is None:
-            raise_error(
-                RuntimeError,
-                "Please provide an observable for expectation value calculation.",
-            )
+            self.observable = Z(self.nqubits, dense=True, backend=self.backend)
         super().__post_init__()
 
     def __call__(self, x: Circuit) -> ndarray:
@@ -96,8 +96,10 @@ def set_backend(self, backend):
         super().set_backend(backend)
         self.observable.backend = backend
 
+    def __hash__(self) -> int:
+        return hash((self.qubits, self.nshots, self.backend, self.observable))
+
 
-@dataclass
 class State(QuantumDecoding):
 
     def __call__(self, x: Circuit) -> ndarray:
@@ -115,7 +117,6 @@ def analytic(self):
         return True
 
 
-@dataclass
 class Samples(QuantumDecoding):
 
     def __post_init__(self):

src/qiboml/models/encoding.py

@@ -1,5 +1,6 @@
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
+from typing import Optional
 
 import numpy as np
 from qibo import Circuit, gates
@@ -12,14 +13,16 @@
 class QuantumEncoding(ABC):
 
     nqubits: int
-    qubits: list[int] = None
+    qubits: Optional[tuple[int]] = None
     _circuit: Circuit = None
 
     def __post_init__(
         self,
     ):
-        if self.qubits is None:
-            self.qubits = list(range(self.nqubits))
+        self.qubits = (
+            tuple(range(self.nqubits)) if self.qubits is None else tuple(self.qubits)
+        )
+
         self._circuit = Circuit(self.nqubits)
 
     @abstractmethod
@@ -36,8 +39,10 @@ def circuit(
     def differentiable(self):
         return True
 
+    def __hash__(self) -> int:
+        return hash(self.qubits)
+
 
-@dataclass
 class PhaseEncoding(QuantumEncoding):
 
     def __post_init__(
@@ -56,7 +61,6 @@ def __call__(self, x: ndarray) -> Circuit:
         return self._circuit
 
 
-@dataclass
 class BinaryEncoding(QuantumEncoding):
 
     def __call__(self, x: ndarray) -> Circuit:

src/qiboml/operations/differentiation.py

@@ -164,25 +164,27 @@ def evaluate(
                 self,
                 "_jacobian",
                 partial(jax.jit, static_argnums=(1, 2, 3))(
-                    jax.jacfwd(self._run, (0,) + self._argnums)
+                    jax.jacfwd(self._run, (0,) + self._argnums),
                 ),
             )
             setattr(
                 self,
                 "_jacobian_without_inputs",
                 partial(jax.jit, static_argnums=(1, 2, 3))(
-                    jax.jacfwd(self._run, self._argnums)
+                    jax.jacfwd(self._run, self._argnums),
                 ),
             )
         parameters = backend.to_numpy(list(parameters))
         parameters = self._jax.cast(parameters, parameters.dtype)
         decoding.set_backend(self._jax)
         if wrt_inputs:
-            gradients = self._jacobian(x, encoding, circuit, decoding, *parameters)
+            gradients = self._jacobian(
+                x, encoding, circuit, decoding, *parameters
+            )  # pylint: disable=no-member
         else:
             gradients = (
                 self._jax.numpy.zeros((decoding.output_shape[-1], x.shape[-1])),
-                self._jacobian_without_inputs(
+                self._jacobian_without_inputs(  # pylint: disable=no-member
                     x, encoding, circuit, decoding, *parameters
                 ),
             )

tests/test_models_decoding.py

@@ -32,9 +32,6 @@ def test_expectation_layer(backend, nshots):
     backend.set_seed(42)
     rng = np.random.default_rng(42)
     nqubits = 5
-    # test observable error
-    with pytest.raises(RuntimeError):
-        layer = dec.Expectation(nqubits, backend=backend)
 
     c = random_clifford(nqubits, seed=rng, backend=backend)
     observable = hamiltonians.SymbolicHamiltonian(