more strict condition for fall back on delta function convolution

changelog.md

@@ -4,6 +4,7 @@
  * move most function related to IO of the command line wrappers into a separate file.
  * make TreeTime own its random number generator and add `--rgn-seed` to control state in CLI. See [PR #234](https://github.com/neherlab/treetime/pull/234)
  * add flag `--greedy-resolve` as inverse to `--stochastic-resolve` with the aim of switching the two.
+ * tighten conditions that trigger approximation of narrow distribution as a delta function in convolution using FFT [PR #235](https://github.com/neherlab/treetime/pull/235).
 
 # 0.9.6: bug fixes and new mode of polytomy resolution
  * in cases when very large polytomies are resolved, the multiplication of the discretized message results in messages/distributions of length 1. This resulted in an error, since interpolation objects require at least two points. This is now caught and a small discrete grid created.

treetime/clock_tree.py

@@ -704,8 +704,13 @@ def _cleanup():
                     if hasattr(self, 'merger_model') and self.merger_model:
                         time_points = parent.marginal_pos_LH.x
                         if len(time_points)<5:
-                            time_points = np.linspace(np.min([x.xmin for x in complementary_msgs]),
-                                                      np.max([x.xmax for x in complementary_msgs]), 50)
+                            time_points = np.unique(np.concatenate([
+                                                        time_points,
+                                                        np.linspace(np.min([x.xmin for x in complementary_msgs]),
+                                                                    np.max([x.xmax for x in complementary_msgs]), 50),
+                                                        np.linspace(np.min([x.effective_support[0] for x in complementary_msgs]),
+                                                                    np.max([x.effective_support[1] for x in complementary_msgs]), 50),
+                                                        ]))
                         # As Lx (the product of child messages) does not include the node contribution this must
                         # be added to recover the full distribution of the parent node w/o contribution of the focal node.
                         complementary_msgs.append(self.merger_model.node_contribution(parent, time_points))

treetime/distribution.py

@@ -272,6 +272,7 @@ def x(self):
     def y(self):
         if self.is_delta:
             print("Warning: evaluating log probability of a delta distribution.")
+            import ipdb; ipdb.set_trace()
             return [self.weight]
         else:
             return self._peak_val + self._func.y
@@ -344,7 +345,7 @@ def calc_effective_support(self, cutoff=1e-15):
 
     def _adjust_grid(self, rel_tol=0.01, yc=10):
         n_iter=0
-        while len(self.y)>200 and n_iter<5:
+        while len(self.x)>200 and n_iter<5:
             interp_err = 2*self.y[1:-1] - self.y[2:] - self.y[:-2]
             ind = np.ones_like(self.y, dtype=bool)
             dy = self.y-self.peak_val

treetime/node_interpolator.py

@@ -168,18 +168,21 @@ def convolve_fft(cls, node_interp, branch_interp, fft_grid_size=FFT_FWHM_GRID_SI
         b_support_range = b_effsupport[1]-b_effsupport[0]
         n_support_range = n_effsupport[1]-n_effsupport[0]
         #ratio = n_support_range/b_support_range
-        ratio = node_interp.fwhm/branch_interp.fwhm
+        ratio = n_support_range/branch_interp.fwhm
 
-        if ratio < 1/fft_grid_size and 4*dt > node_interp.fwhm:
-            ## node distribution is much narrower than the branch distribution, proceed as if node distribution is
-            ## a delta distribution
+        if ratio < 1/fft_grid_size and 4.0*dt > node_interp.fwhm:
+            ## node distribution is much narrower than the branch distribution, proceed as if
+            # node distribution is a delta distribution with the peak 4 full-width-half-maxima
+            # away from the nominal peak to avoid slicing the relevant range to zero
             log_scale_node_interp = node_interp.integrate(return_log=True, a=node_interp.xmin,b=node_interp.xmax,n=max(100, len(node_interp.x))) #probability of node distribution
             if inverse_time:
-                x = branch_interp.x + node_interp._peak_pos
-                dist = Distribution(x, branch_interp(x - node_interp._peak_pos) - log_scale_node_interp, min_width=max(node_interp.min_width, branch_interp.min_width), is_log=True)
+                x = branch_interp.x + max(n_effsupport[0], node_interp._peak_pos - 4.0*node_interp.fwhm)
+                dist = Distribution(x, branch_interp(x - node_interp._peak_pos) - log_scale_node_interp,
+                                    min_width=max(node_interp.min_width, branch_interp.min_width), is_log=True)
             else:
-                x = - branch_interp.x + node_interp._peak_pos
-                dist = Distribution(x, branch_interp(branch_interp.x) - log_scale_node_interp, min_width=max(node_interp.min_width, branch_interp.min_width), is_log=True)
+                x = - branch_interp.x + min(n_effsupport[1], node_interp._peak_pos + 4.0*node_interp.fwhm)
+                dist = Distribution(x, branch_interp(branch_interp.x) - log_scale_node_interp,
+                                    min_width=max(node_interp.min_width, branch_interp.min_width), is_log=True)
             return dist
         elif ratio > fft_grid_size and 4*dt > branch_interp.fwhm:
             raise ValueError("ERROR: Unexpected behavior: branch distribution is much narrower than the node distribution.")

treetime/wrappers.py

@@ -325,7 +325,7 @@ def timetree(params):
     if params.aln is None and params.sequence_length is None:
         print("one of arguments '--aln' and '--sequence-length' is required.", file=sys.stderr)
         return 1
-    print(f"rng_seed: {params.rng_seed}")
+
     myTree = TreeTime(dates=dates, tree=params.tree, ref=ref,
                       aln=aln, gtr=gtr, seq_len=params.sequence_length,
                       verbose=params.verbose, fill_overhangs=not params.keep_overhangs,
@@ -379,7 +379,6 @@ def run_timetree(myTree, params, outdir, tree_suffix='', prune_short=True, metho
     if hasattr(params, 'stochastic_resolve'):
         stochastic_resolve = params.stochastic_resolve
     else: stochastic_resolve = False
-    print(f"stochastic_resolve: {stochastic_resolve}")
 
     # determine whether confidence intervals are to be computed and how the
     # uncertainty in the rate estimate should be treated