catch possible exception in fit error calculation, maybe source of #39

src/nmreval/fit/minimizer.py

@@ -14,6 +14,8 @@ from .result import FitResultCreator
 
 __all__ = ['FitRoutine', 'FitAbortException']
 
+from ..lib.logger import logger
+
 
 class FitAbortException(Exception):
     pass
@@ -464,11 +466,18 @@ class FitRoutine(object):
     def _calc_error(jac, chi, nobs, nvars):
         # copy of scipy.curve_fit to calculate covariance
         # noinspection PyTupleAssignmentBalance
-        _, s, vt = la.svd(jac, full_matrices=False)
-        threshold = EPS * max(jac.shape) * s[0]
-        s = s[s > threshold]
-        vt = vt[:s.size]
-        pcov = np.dot(vt.T / s**2, vt) * chi / (nobs - nvars)
+        try:
+            _, s, vt = la.svd(jac, full_matrices=False)
+        except ValueError as e:
+            # this may be issue #39: On entry to DGESSD parameter had an illegal value
+            # catch this exception and ignore error calculation
+            logger.error(f'Error calculation failed with {e.args}')
+            pcov = None
+        else:
+            threshold = EPS * max(jac.shape) * s[0]
+            s = s[s > threshold]
+            vt = vt[:s.size]
+            pcov = np.dot(vt.T / s**2, vt) * chi / (nobs - nvars)
 
         if pcov is None:
             _err = np.zeros(nvars)