Make covariance fields in display easier to understand

src/functionminimum.cpp

@@ -25,6 +25,18 @@ FunctionMinimum init2(const MnUserTransformation& tr, py::sequence par,
 py::tuple fmin_getstate(const FunctionMinimum&);
 FunctionMinimum fmin_setstate(py::tuple);
 
+bool hesse_failed_workaround(const FunctionMinimum& self) {
+  // Calling FunctionMinimum::HesseFailed is not reliable.
+  // It calls MinimumError::HesseFailed, but this is false if
+  // there were the failures MinimumError::MnReachedCallLimit
+  // or MinimumError::MnInvertFailed, which cannot be queried
+  // from FunctionMinimum.
+  //
+  // As a workaround, we return true if covariance exists, but
+  // is not accurate or made positive definite.
+  return self.HasCovariance() && !(self.HasPosDefCovar() || self.HasMadePosDefCovar());
+}
+
 void bind_functionminimum(py::module m) {
   py::class_<FunctionMinimum>(m, "FunctionMinimum")
 
@@ -42,7 +54,7 @@ void bind_functionminimum(py::module m) {
       .def_property_readonly("has_posdef_covar", &FunctionMinimum::HasPosDefCovar)
       .def_property_readonly("has_made_posdef_covar",
                              &FunctionMinimum::HasMadePosDefCovar)
-      .def_property_readonly("hesse_failed", &FunctionMinimum::HesseFailed)
+      .def_property_readonly("hesse_failed", hesse_failed_workaround)
       .def_property_readonly("has_covariance", &FunctionMinimum::HasCovariance)
       .def_property_readonly("is_above_max_edm", &FunctionMinimum::IsAboveMaxEdm)
       .def_property_readonly("has_reached_call_limit",

src/iminuit/_repr_html.py

@@ -93,26 +93,30 @@ def good(x, should_be, alt_style=bad_style):
 
 def fmin(fm):
     ff = fmin_fields(fm)
+    if fm.hesse_failed:
+        cov_style = bad_style
+    elif fm.has_accurate_covar:
+        cov_style = good_style
+    else:
+        cov_style = warn_style
     return to_str(
         table(
             tr(
                 th(
                     ff[0],
-                    colspan=5,
+                    colspan=2,
                     style="text-align:center",
                     title="Minimizer",
                 ),
             ),
             tr(
                 td(
                     ff[1],
-                    colspan=2,
                     style="text-align:left",
                     title="Minimum value of function",
                 ),
                 td(
                     ff[2],
-                    colspan=3,
                     style="text-align:center",
                     title=(
                         "Total number of function and (optional) gradient evaluations"
@@ -122,68 +126,39 @@ def fmin(fm):
             tr(
                 td(
                     ff[3],
-                    colspan=2,
                     style="text-align:left",
                     title="Estimated distance to minimum and goal",
                 ),
                 td(
                     ff[4],
-                    colspan=3,
                     style="text-align:center",
                     title="Total run time of algorithms",
                 ),
             ),
             tr(
                 td(
                     ff[5],
-                    colspan=2,
                     style="text-align:center;" + good(fm.is_valid, True),
                 ),
                 td(
                     ff[6],
-                    colspan=3,
-                    style="text-align:center;"
-                    + good(fm.has_parameters_at_limit, False, warn_style),
+                    style="text-align:center;" + good(fm.is_above_max_edm, False),
                 ),
             ),
             tr(
                 td(
                     ff[7],
-                    colspan="2",
-                    style="text-align:center;" + good(fm.is_above_max_edm, False),
+                    style="text-align:center;"
+                    + good(fm.has_parameters_at_limit, False, warn_style),
                 ),
                 td(
                     ff[8],
-                    colspan=3,
                     style="text-align:center;" + good(fm.has_reached_call_limit, False),
                 ),
             ),
             tr(
-                td(
-                    ff[9],
-                    style="text-align:center;"
-                    + good(fm.has_covariance, True, warn_style),
-                ),
-                td(
-                    ff[10],
-                    style="text-align:center;" + good(fm.hesse_failed, False),
-                ),
-                td(
-                    ff[11],
-                    title="Is covariance matrix accurate?",
-                    style="text-align:center;"
-                    + good(fm.has_accurate_covar, True, warn_style),
-                ),
-                td(
-                    ff[12],
-                    style="text-align:center;" + good(fm.has_posdef_covar, True),
-                    title="Is covariance matrix positive definite?",
-                ),
-                td(
-                    ff[13],
-                    style="text-align:center;" + good(fm.has_made_posdef_covar, False),
-                    title="Was positive definiteness enforced by Minuit?",
-                ),
+                td(ff[9], style="text-align:center;" + cov_style),
+                td(ff[10], style="text-align:center;" + cov_style),
             ),
         )
     )

src/iminuit/_repr_text.py

@@ -51,21 +51,39 @@ def fmin_fields(fm):
     s_ncall = f"Nfcn = {fm.nfcn}"
     if fm.ngrad > 0:
         s_ncall += f", Ngrad = {fm.ngrad}"
+
+    if fm.hesse_failed:
+        covariance_msg1 = "Hesse FAILED"
+        if fm.has_reached_call_limit:
+            covariance_msg2 = "ABOVE call limit"
+        else:
+            assert not fm.has_posdef_covar
+            covariance_msg2 = "Covariance NOT pos. def."
+    else:
+        if fm.has_covariance:
+            covariance_msg1 = "Hesse ok"
+            if fm.has_accurate_covar:
+                covariance_msg2 = "Covariance accurate"
+            elif fm.has_made_posdef_covar:
+                covariance_msg2 = "Covariance FORCED pos. def."
+            else:
+                covariance_msg2 = "Covariance APPROXIMATE"
+        else:
+            covariance_msg1 = "Hesse not run"
+            covariance_msg2 = "NO covariance"
+
     return [
         f"{fm.algorithm}",
         f"FCN = {fm.fval:.4g}" + (f" (χ²/ndof = {rc:.1f})" if not np.isnan(rc) else ""),
         s_ncall,
         f"EDM = {fm.edm:.3g} (Goal: {fm.edm_goal:.3g})",
         f"time = {fm.time:.1f} sec" if fm.time >= 0.1 else "",
         f"{'Valid' if fm.is_valid else 'INVALID'} Minimum",
-        f"{'SOME' if fm.has_parameters_at_limit else 'No'} Parameters at limit",
         f"{'ABOVE' if fm.is_above_max_edm else 'Below'} EDM threshold (goal x 10)",
+        f"{'SOME' if fm.has_parameters_at_limit else 'No'} parameters at limit",
         f"{'ABOVE' if fm.has_reached_call_limit else 'Below'} call limit",
-        f"{'' if fm.has_covariance else 'NO '}Covariance",
-        f"Hesse {'FAILED' if fm.hesse_failed else 'ok'}",
-        "Accurate" if fm.has_accurate_covar else "APPROXIMATE",
-        "Pos. def." if fm.has_posdef_covar else "NOT pos. def.",
-        "FORCED" if fm.has_made_posdef_covar else "Not forced",
+        covariance_msg1,
+        covariance_msg2,
     ]
 
 
@@ -82,11 +100,10 @@ def fmin(fm):
     l3 = format_line(w, "├┼┤")
     v1 = format_row(w, *ff[5:7])
     l4 = format_line(w, "├┼┤")
-    v2 = format_row((34, 38), *ff[7:9])
-    w = (15, 18, 11, 13, 12)
-    l5 = format_line(w, "├┬┼┬┬┤")
-    v3 = format_row(w, *ff[9:14])
-    l6 = format_line(w, "└┴┴┴┴┘")
+    v2 = format_row(w, *ff[7:9])
+    l5 = format_line(w, "├┼┤")
+    v3 = format_row(w, *ff[9:])
+    l6 = format_line(w, "└┴┘")
     return "\n".join((l1, i1, l2, i2, i3, l3, v1, l4, v2, l5, v3, l6))
 
 

tests/fmin_approximate.txt

@@ -0,0 +1,12 @@
+┌─────────────────────────────────────────────────────────────────────────┐
+│                                Migrad                                   │
+├──────────────────────────────────┬──────────────────────────────────────┤
+│ FCN = 11.46 (χ²/ndof = 1.1)      │         Nfcn = 10, Ngrad = 3         │
+│ EDM = 1.23e-10 (Goal: 0.0001)    │                                      │
+├──────────────────────────────────┼──────────────────────────────────────┤
+│          Valid Minimum           │   Below EDM threshold (goal x 10)    │
+├──────────────────────────────────┼──────────────────────────────────────┤
+│      No parameters at limit      │           Below call limit           │
+├──────────────────────────────────┼──────────────────────────────────────┤
+│             Hesse ok             │        Covariance APPROXIMATE        │
+└──────────────────────────────────┴──────────────────────────────────────┘

tests/fmin_bad.html

@@ -1,28 +1,25 @@
 <table>
     <tr>
-        <th colspan="5" style="text-align:center" title="Minimizer"> SciPy[L-BFGS-B] </th>
+        <th colspan="2" style="text-align:center" title="Minimizer"> SciPy[L-BFGS-B] </th>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:left" title="Minimum value of function"> FCN = nan </td>
-        <td colspan="3" style="text-align:center" title="Total number of function and (optional) gradient evaluations"> Nfcn = 100000, Ngrad = 200000 </td>
+        <td style="text-align:left" title="Minimum value of function"> FCN = nan </td>
+        <td style="text-align:center" title="Total number of function and (optional) gradient evaluations"> Nfcn = 100000, Ngrad = 200000 </td>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:left" title="Estimated distance to minimum and goal"> EDM = 1.23e-10 (Goal: 1e-05) </td>
-        <td colspan="3" style="text-align:center" title="Total run time of algorithms"> time = 1.2 sec </td>
+        <td style="text-align:left" title="Estimated distance to minimum and goal"> EDM = 1.23e-10 (Goal: 1e-05) </td>
+        <td style="text-align:center" title="Total run time of algorithms"> time = 1.2 sec </td>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:center;{bad}"> INVALID Minimum </td>
-        <td colspan="3" style="text-align:center;{warn}"> SOME Parameters at limit </td>
+        <td style="text-align:center;{bad}"> INVALID Minimum </td>
+        <td style="text-align:center;{bad}"> ABOVE EDM threshold (goal x 10) </td>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:center;{bad}"> ABOVE EDM threshold (goal x 10) </td>
-        <td colspan="3" style="text-align:center;{bad}"> ABOVE call limit </td>
+        <td style="text-align:center;{warn}"> SOME parameters at limit </td>
+        <td style="text-align:center;{bad}"> ABOVE call limit </td>
     </tr>
     <tr>
-        <td style="text-align:center;{warn}"> NO Covariance </td>
         <td style="text-align:center;{bad}"> Hesse FAILED </td>
-        <td style="text-align:center;{warn}" title="Is covariance matrix accurate?"> APPROXIMATE </td>
-        <td style="text-align:center;{bad}" title="Is covariance matrix positive definite?"> NOT pos. def. </td>
-        <td style="text-align:center;{bad}" title="Was positive definiteness enforced by Minuit?"> FORCED </td>
+        <td style="text-align:center;{bad}"> ABOVE call limit </td>
     </tr>
 </table>

tests/fmin_bad.txt

@@ -4,9 +4,9 @@
 │ FCN = nan                        │    Nfcn = 100000, Ngrad = 200000     │
 │ EDM = 1.23e-10 (Goal: 1e-05)     │            time = 1.2 sec            │
 ├──────────────────────────────────┼──────────────────────────────────────┤
-│         INVALID Minimum          │       SOME Parameters at limit       │
+│         INVALID Minimum          │   ABOVE EDM threshold (goal x 10)    │
 ├──────────────────────────────────┼──────────────────────────────────────┤
-│ ABOVE EDM threshold (goal x 10)  │           ABOVE call limit           │
-├───────────────┬──────────────────┼───────────┬─────────────┬────────────┤
-│ NO Covariance │   Hesse FAILED   │APPROXIMATE│NOT pos. def.│   FORCED   │
-└───────────────┴──────────────────┴───────────┴─────────────┴────────────┘
+│     SOME parameters at limit     │           ABOVE call limit           │
+├──────────────────────────────────┼──────────────────────────────────────┤
+│           Hesse FAILED           │           ABOVE call limit           │
+└──────────────────────────────────┴──────────────────────────────────────┘

tests/fmin_good.html

@@ -1,28 +1,25 @@
 <table>
     <tr>
-        <th colspan="5" style="text-align:center" title="Minimizer"> Migrad </th>
+        <th colspan="2" style="text-align:center" title="Minimizer"> Migrad </th>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:left" title="Minimum value of function"> FCN = 11.46 (χ²/ndof = 1.1) </td>
-        <td colspan="3" style="text-align:center" title="Total number of function and (optional) gradient evaluations"> Nfcn = 10, Ngrad = 3 </td>
+        <td style="text-align:left" title="Minimum value of function"> FCN = 11.46 (χ²/ndof = 1.1) </td>
+        <td style="text-align:center" title="Total number of function and (optional) gradient evaluations"> Nfcn = 10, Ngrad = 3 </td>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:left" title="Estimated distance to minimum and goal"> EDM = 1.23e-10 (Goal: 0.0001) </td>
-        <td colspan="3" style="text-align:center" title="Total run time of algorithms">  </td>
+        <td style="text-align:left" title="Estimated distance to minimum and goal"> EDM = 1.23e-10 (Goal: 0.0001) </td>
+        <td style="text-align:center" title="Total run time of algorithms">  </td>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:center;{good}"> Valid Minimum </td>
-        <td colspan="3" style="text-align:center;{good}"> No Parameters at limit </td>
+        <td style="text-align:center;{good}"> Valid Minimum </td>
+        <td style="text-align:center;{good}"> Below EDM threshold (goal x 10) </td>
     </tr>
     <tr>
-        <td colspan="2" style="text-align:center;{good}"> Below EDM threshold (goal x 10) </td>
-        <td colspan="3" style="text-align:center;{good}"> Below call limit </td>
+        <td style="text-align:center;{good}"> No parameters at limit </td>
+        <td style="text-align:center;{good}"> Below call limit </td>
     </tr>
     <tr>
-        <td style="text-align:center;{good}"> Covariance </td>
         <td style="text-align:center;{good}"> Hesse ok </td>
-        <td style="text-align:center;{good}" title="Is covariance matrix accurate?"> Accurate </td>
-        <td style="text-align:center;{good}" title="Is covariance matrix positive definite?"> Pos. def. </td>
-        <td style="text-align:center;{good}" title="Was positive definiteness enforced by Minuit?"> Not forced </td>
+        <td style="text-align:center;{good}"> Covariance accurate </td>
     </tr>
 </table>

tests/fmin_good.txt

@@ -4,9 +4,9 @@
 │ FCN = 11.46 (χ²/ndof = 1.1)      │         Nfcn = 10, Ngrad = 3         │
 │ EDM = 1.23e-10 (Goal: 0.0001)    │                                      │
 ├──────────────────────────────────┼──────────────────────────────────────┤
-│          Valid Minimum           │        No Parameters at limit        │
+│          Valid Minimum           │   Below EDM threshold (goal x 10)    │
 ├──────────────────────────────────┼──────────────────────────────────────┤
-│ Below EDM threshold (goal x 10)  │           Below call limit           │
-├───────────────┬──────────────────┼───────────┬─────────────┬────────────┤
-│  Covariance   │     Hesse ok     │ Accurate  │  Pos. def.  │ Not forced │
-└───────────────┴──────────────────┴───────────┴─────────────┴────────────┘
+│      No parameters at limit      │           Below call limit           │
+├──────────────────────────────────┼──────────────────────────────────────┤
+│             Hesse ok             │         Covariance accurate          │
+└──────────────────────────────────┴──────────────────────────────────────┘