Merge pull request #688 from evalf/niter

Niter

CHANGELOG.rst

@@ -9,6 +9,14 @@ features in inverse chronological order.
 New in v8.0 (in development)
 ----------------------------
 
+- New: iteration count via info.niter
+
+  The info struct returned by ``solve_withinfo`` newly contains the amount of
+  iterations as the ``niter`` attribute:
+
+  >>> res, info = solver.newton('u:v', res).solve_withinfo(1e-10, maxiter=10)
+  >>> assert info.niter <= 10
+
 - New: test fields and residual functionals
 
   The :mod:`nutils.solver` methods have been generalized to accept scalar

nutils/solver.py

@@ -153,14 +153,13 @@ def solve_withinfo(self, tol, maxiter=float('inf'), miniter=0):
         if miniter > maxiter:
             raise ValueError('The minimum number of iterations cannot be larger than the maximum.')
         with log.iter.wrap(_progress(self._wrapped.__class__.__name__, tol), self) as items:
-            i = 0
-            for lhs, info in items:
+            for i, (lhs, info) in enumerate(items):
                 if info.resnorm <= tol and i >= miniter:
                     break
                 if i > maxiter:
                     raise SolverError('failed to reach target tolerance')
-                i += 1
-            log.info('converged in {} steps to residual {:.1e}'.format(i, info.resnorm))
+            log.info(f'converged in {i} steps to residual {info.resnorm:.1e}')
+        info.niter = i
         return lhs, info