simple incremental sim using dirty flags

src/kyupy/__init__.py

@@ -111,7 +111,7 @@ class Timer:
 
 
 class Timers:
-    def __init__(self, t={}): self.timers = defaultdict(Timer) | t
+    def __init__(self, t={}): self.timers: dict[str, Timer] = defaultdict(Timer) | t
     def __getitem__(self, name): return self.timers[name]
     def __repr__(self): return '{' + ', '.join([f'{k}: {v}' for k, v in self.timers.items()]) + '}'
     def __add__(self, t):

src/kyupy/logic_sim.py

@@ -356,6 +356,19 @@ class LogicSim2V(sim.SimOps):
         Storage locations are indirectly addressed.
         Data for line `l` is in `self.c[self.c_locs[l]]`.
         """
+        self.c_dirty = np.full(self.c_len, 1, dtype=np.uint8)
+        """Marker for logic values that have changed recently for use in incremental simulation.
+
+        A node n will be evaluated by `c_prop()` if and only if at least one of its inputs is marked dirty (`c_dirty[c_locs[n.ins[i]]] == 1`).
+        If a node is evaluated, its output is marked dirty.
+        By default, this array is all-1, therefore every node is evaluated every time by `c_prop()`.
+        Enable incremental simulation by setting this array to all-0, change signal values in `c` and set `c_dirty` to 1 for all changed signals.
+        Next call to `c_prop()` will only evaluate nodes that read from the changed signals.
+        To restore the original simulation state, revert the signal value changes in `c`, and call `c_prop()` again.
+        Caveats:
+        - Injected changes that are located downstream of other changes will have no effect.
+        - Only works with `c_reuse=False` (default).
+        """
         self.s_assign = np.zeros((self.s_len, self.sims), dtype=np.uint8)
         """Logic values assigned to the ports and flip-flops of the circuit.
 
@@ -390,7 +403,7 @@ class LogicSim2V(sim.SimOps):
                 fault_mask2 = np.full(self.c.shape[-1], 0, dtype=np.uint8)
                 fault_mask2[:len(fault_mask)] = fault_mask
                 fault_mask = fault_mask2
-        c_prop_2v_cpu(self.ops, self.c_locs, self.c, int(fault_line), fault_mask, int(fault_model))
+        c_prop_2v_cpu(self.ops, self.c_locs, self.c, self.c_dirty, int(fault_line), fault_mask, int(fault_model))
 
     def c_to_s(self):
         """Captures the results of the combinational portion into ``self.s_result``.
@@ -424,9 +437,11 @@ class LogicSim2V(sim.SimOps):
 
 
 @numba.njit
-def c_prop_2v_cpu(ops, c_locs, c, fault_line, fault_mask, fault_model):
+def c_prop_2v_cpu(ops, c_locs, c, c_dirty, fault_line, fault_mask, fault_model):
     for op, o0l, i0l, i1l, i2l, i3l in ops[:,:6]:
         o0, i0, i1, i2, i3 = [c_locs[x] for x in (o0l, i0l, i1l, i2l, i3l)]
+        if fault_line < 0 or o0l != fault_line:  # fault injection forces node evaluation
+            if not (c_dirty[i0] | c_dirty[i1] | c_dirty[i2] | c_dirty[i3]): continue
         if op == sim.BUF1: c[o0]=c[i0]
         elif op == sim.INV1: c[o0] = ~c[i0]
         elif op == sim.AND2: c[o0] = c[i0] & c[i1]
@@ -466,8 +481,9 @@ def c_prop_2v_cpu(ops, c_locs, c, fault_line, fault_mask, fault_model):
                 c[o0] = c[o0] & ~fault_mask
             elif fault_model == 1:
                 c[o0] = c[o0] | fault_mask
-            else:
+            elif fault_model == 2:
                 c[o0] = c[o0] ^ fault_mask
+        c_dirty[o0] = 1
 
 
 class LogicSim4V(sim.SimOps):