Fix bugs in fixed burnin

bilby/core/sampler/ptemcee.py

@@ -648,8 +648,8 @@ def check_iteration(
     nwalkers, nsteps, ndim = samples.shape
 
     # Compute ACT tau for 0-temperature chains
+    tau_array = np.zeros((nwalkers, ndim))
     if nsteps > ci.burn_in_fixed_discard:
-        tau_array = np.zeros((nwalkers, ndim))
         for ii in range(nwalkers):
             for jj, key in enumerate(search_parameter_keys):
                 if ci.ignore_keys_for_tau and ci.ignore_keys_for_tau in key:
@@ -662,7 +662,7 @@ def check_iteration(
                 except emcee.autocorr.AutocorrError:
                     tau_array[ii, jj] = np.inf
     else:
-        tau_array = np.ones((nwalkers, ndim)) * np.inf
+        tau_array += np.inf
 
     # Maximum over parameters, mean over walkers
     tau = np.max(np.mean(tau_array, axis=0))
@@ -678,16 +678,16 @@ def check_iteration(
     Q = get_Q_convergence(samples)
     Q_list.append(Q)
 
-    # Convert to an integer
-    tau_int = int(np.ceil(tau)) if not np.isnan(tau) else tau
-
-    if np.isnan(tau_int) or np.isinf(tau_int):
+    if np.isnan(tau) or np.isinf(tau):
         print_progress(
             iteration, sampler, time_per_check, np.nan, np.nan,
-            np.nan, np.nan, False, convergence_inputs,
+            np.nan, np.nan, False, convergence_inputs, np.nan,
         )
         return False, np.nan, np.nan, np.nan, np.nan
 
+    # Convert to an integer
+    tau_int = int(np.ceil(tau))
+
     # Calculate the effective number of samples available
     nburn = ci.burn_in_fixed_discard + int(ci.burn_in_nact * tau_int)
     thin = int(np.max([1, ci.thin_by_nact * tau_int]))
@@ -890,8 +890,8 @@ def plot_walkers(walkers, nburn, thin, parameter_labels, outdir, label,
         for i, (ax, axh) in enumerate(axes):
             ax.plot(
                 idxs[: nburn_fixed],
-                walkers[:, : nburn, i].T,
-                color="k",
+                walkers[:, : nburn_fixed, i].T,
+                color="gray",
                 **scatter_kwargs
             )