Add print_stats method to ode and implement for CVODE integrator

`CVODE` solver has function `CVodePrintAllStats` that prints statistics about
integrator such as number of right-hand-side function evaluations and number
of nonlinear solves.

packages/scikits-odes-sundials/src/scikits_odes_sundials/c_cvode.pxd

@@ -120,6 +120,7 @@ cdef extern from "cvode/cvode.h":
     int CVodeGetNumNonlinSolvConvFails(void *cvode_mem, long int *nncfails)
     int CVodeGetNonlinSolvStats(void *cvode_mem, long int *nniters,
                                             long int *nncfails)
+    int CVodePrintAllStats(void* cvode_mem, FILE* outfile, SUNOutputFormat fmt)
     char *CVodeGetReturnFlagName(long int flag)
     void CVodeFree(void **cvode_mem)
 

packages/scikits-odes-sundials/src/scikits_odes_sundials/c_sundials.pxd

@@ -4,6 +4,10 @@ cdef extern from "sundials/sundials_types.h":
     ctypedef float sunrealtype
     ctypedef unsigned int sunbooleantype
     ctypedef long sunindextype
+
+    cdef enum SUNOutputFormat:
+        SUN_OUTPUTFORMAT_TABLE,
+        SUN_OUTPUTFORMAT_CSV
 
 cdef extern from "sundials/sundials_context.h":
     struct _SUNContext:

packages/scikits-odes-sundials/src/scikits_odes_sundials/cvode.pyx

@@ -10,13 +10,15 @@ include "sundials_config.pxi"
 import numpy as np
 cimport numpy as np
 
+from libc cimport stdio
+
 from . import (
     CVODESolveFailed, CVODESolveFoundRoot, CVODESolveReachedTSTOP,
     _get_num_args,
 )
 
 from .c_sundials cimport (
-    sunrealtype, N_Vector, SUNContext_Create, SUNContext_Free,
+    sunrealtype, N_Vector, SUNContext_Create, SUNContext_Free, SUN_OUTPUTFORMAT_TABLE
 )
 from .c_nvector_serial cimport *
 from .c_sunmatrix cimport *
@@ -2048,6 +2050,9 @@ cdef class CVODE:
                          'NumRhsEvalsJtimesFD': nfevalsLS})
 
         return info
+
+    def print_stats(self):
+        CVodePrintAllStats(self._cv_mem, stdio.stdout, SUN_OUTPUTFORMAT_TABLE)
 
     def __dealloc__(self):
         if self._cv_mem is not NULL: CVodeFree(&self._cv_mem)

packages/scikits-odes/src/scikits_odes/ode.py

@@ -306,6 +306,12 @@ def get_info(self):
         else:
             return {}
 
+    def print_stats(self):
+        if hasattr(self._integrator, "print_stats"):
+            self._integrator.print_stats()
+        else:
+            print(f"Method `print_stats` is not implemented for integrator {self._integrator}")
+
 #------------------------------------------------------------------------------
 # ODE integrators
 #------------------------------------------------------------------------------