feat: Reset to zero for Leaky

Context

The goal of this MR is to add an option to select a soft reset (subtraction, eq.1 ) or a hard reset (reset to zero, eq. 2) when creating a Leaky Operator.

U[t+1] = βU[t] + I_{in}[t+1] - RU_{thr} \tag{1}

U[t+1] = βU[t] + I_{in}[t+1] - R(βU[t] + I_{in}[t+1]) \tag{2}

Note that for the implementation of hard reset, the potential is reset to zero in the next step, so if we have a spike at step s=0, then we start s=1 by setting the memory to zero, and proceed with computing the potential by taking the input.

Modified files

• MetaOperatorDefs.hpp: Add a LeakyReset enum and change Leaky constructor;
• Leaky.cpp : Use the additional LeakyReset constructor parameter to create the Leaky node;
• pybind_MetaOperator.cpp: reflect the changes made to the constructor;
• Test_MetaOperator.cpp: Test the instanciation of a Leaky node with reset to zero;

Note: More tests have alaredy been written in aidge_backend_cpu to assert that the behaviour is correct.

Related issue

Fix #219

python_binding/operator/pybind_MetaOperatorDefs.cpp

@@ -400,6 +400,18 @@ void declare_LSTMOp(py::module &m) {
     )mydelimiter");
 }
 
+void declare_LeakyResetEnum(py::module &m) {
+    py::enum_<LeakyReset>(m, "leaky_reset", R"doc(
+        Enumeration for the Leaky neuron reset mode.
+
+        Subtraction: Membrane potential is subtracted by threshold upon spiking.
+        ToZero     : Membrane potential is forced to 0 upon spiking.
+    )doc")
+        .value("subtraction", LeakyReset::Subtraction)
+        .value("to_zero", LeakyReset::ToZero)
+        .export_values();
+}
+
 
 void declare_LeakyOp(py::module &m) {
     m.def("Leaky", &Leaky,
@@ -441,6 +453,7 @@ void init_MetaOperatorDefs(py::module &m) {
   declare_PaddedMaxPoolingOp<2>(m);
 //   declare_PaddedMaxPoolingOp<3>(m);
   declare_LSTMOp(m);
+  declare_LeakyResetEnum(m);
   declare_LeakyOp(m);
 
   py::class_<MetaOperator_Op, std::shared_ptr<MetaOperator_Op>, OperatorTensor>(m, "MetaOperatorOp", py::multiple_inheritance())