Ch.1 IndexError when using learn.fine_tune in examples

[MaxThone]

Hi,

When running the examples in Chapter 1, I get the stack trace below when doing learn.fine_tune(1). specifically the error seems to be happening in the combine_scheds method.

Note: I'm running the code on a Databricks notebook, not on Jupyter, but for this particular error I don't think this should matter.

Stacktrace

<command-13768> in <module>
----> 1 learn.fine_tune(1)

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/utils.py in _f(*args, **kwargs)
    452         init_args.update(log)
    453         setattr(inst, 'init_args', init_args)
--> 454         return inst if to_return else f(*args, **kwargs)
    455     return _f
    456 

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/callback/schedule.py in fine_tune(self, epochs, base_lr, freeze_epochs, lr_mult, pct_start, div, **kwargs)
    159     "Fine tune with `freeze` for `freeze_epochs` then with `unfreeze` from `epochs` using discriminative LR"
    160     self.freeze()
--> 161     self.fit_one_cycle(freeze_epochs, slice(base_lr), pct_start=0.99, **kwargs)
    162     base_lr /= 2
    163     self.unfreeze()

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/utils.py in _f(*args, **kwargs)
    452         init_args.update(log)
    453         setattr(inst, 'init_args', init_args)
--> 454         return inst if to_return else f(*args, **kwargs)
    455     return _f
    456 

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/callback/schedule.py in fit_one_cycle(self, n_epoch, lr_max, div, div_final, pct_start, wd, moms, cbs, reset_opt)
    111     scheds = {'lr': combined_cos(pct_start, lr_max/div, lr_max, lr_max/div_final),
    112               'mom': combined_cos(pct_start, *(self.moms if moms is None else moms))}
--> 113     self.fit(n_epoch, cbs=ParamScheduler(scheds)+L(cbs), reset_opt=reset_opt, wd=wd)
    114 
    115 # Cell

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/utils.py in _f(*args, **kwargs)
    452         init_args.update(log)
    453         setattr(inst, 'init_args', init_args)
--> 454         return inst if to_return else f(*args, **kwargs)
    455     return _f
    456 

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in fit(self, n_epoch, lr, wd, cbs, reset_opt)
    202             self.opt.set_hypers(lr=self.lr if lr is None else lr)
    203             self.n_epoch,self.loss = n_epoch,tensor(0.)
--> 204             self._with_events(self._do_fit, 'fit', CancelFitException, self._end_cleanup)
    205 
    206     def _end_cleanup(self): self.dl,self.xb,self.yb,self.pred,self.loss = None,(None,),(None,),None,None

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _with_events(self, f, event_type, ex, final)
    153 
    154     def _with_events(self, f, event_type, ex, final=noop):
--> 155         try:       self(f'before_{event_type}')       ;f()
    156         except ex: self(f'after_cancel_{event_type}')
    157         finally:   self(f'after_{event_type}')        ;final()

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _do_fit(self)
    192         for epoch in range(self.n_epoch):
    193             self.epoch=epoch
--> 194             self._with_events(self._do_epoch, 'epoch', CancelEpochException)
    195 
    196     @log_args(but='cbs')

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _with_events(self, f, event_type, ex, final)
    153 
    154     def _with_events(self, f, event_type, ex, final=noop):
--> 155         try:       self(f'before_{event_type}')       ;f()
    156         except ex: self(f'after_cancel_{event_type}')
    157         finally:   self(f'after_{event_type}')        ;final()

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _do_epoch(self)
    186 
    187     def _do_epoch(self):
--> 188         self._do_epoch_train()
    189         self._do_epoch_validate()
    190 

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _do_epoch_train(self)
    178     def _do_epoch_train(self):
    179         self.dl = self.dls.train
--> 180         self._with_events(self.all_batches, 'train', CancelTrainException)
    181 
    182     def _do_epoch_validate(self, ds_idx=1, dl=None):

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _with_events(self, f, event_type, ex, final)
    153 
    154     def _with_events(self, f, event_type, ex, final=noop):
--> 155         try:       self(f'before_{event_type}')       ;f()
    156         except ex: self(f'after_cancel_{event_type}')
    157         finally:   self(f'after_{event_type}')        ;final()

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in all_batches(self)
    159     def all_batches(self):
    160         self.n_iter = len(self.dl)
--> 161         for o in enumerate(self.dl): self.one_batch(*o)
    162 
    163     def _do_one_batch(self):

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in one_batch(self, i, b)
    174         self.iter = i
    175         self._split(b)
--> 176         self._with_events(self._do_one_batch, 'batch', CancelBatchException)
    177 
    178     def _do_epoch_train(self):

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _with_events(self, f, event_type, ex, final)
    153 
    154     def _with_events(self, f, event_type, ex, final=noop):
--> 155         try:       self(f'before_{event_type}')       ;f()
    156         except ex: self(f'after_cancel_{event_type}')
    157         finally:   self(f'after_{event_type}')        ;final()

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in __call__(self, event_name)
    131     def ordered_cbs(self, event): return [cb for cb in sort_by_run(self.cbs) if hasattr(cb, event)]
    132 
--> 133     def __call__(self, event_name): L(event_name).map(self._call_one)
    134 
    135     def _call_one(self, event_name):

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/foundation.py in map(self, f, *args, **kwargs)
    381              else f.format if isinstance(f,str)
    382              else f.__getitem__)
--> 383         return self._new(map(g, self))
    384 
    385     def filter(self, f, negate=False, **kwargs):

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/foundation.py in _new(self, items, *args, **kwargs)
    331     @property
    332     def _xtra(self): return None
--> 333     def _new(self, items, *args, **kwargs): return type(self)(items, *args, use_list=None, **kwargs)
    334     def __getitem__(self, idx): return self._get(idx) if is_indexer(idx) else L(self._get(idx), use_list=None)
    335     def copy(self): return self._new(self.items.copy())

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/foundation.py in __call__(cls, x, *args, **kwargs)
     45             return x
     46 
---> 47         res = super().__call__(*((x,) + args), **kwargs)
     48         res._newchk = 0
     49         return res

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/foundation.py in __init__(self, items, use_list, match, *rest)
    322         if items is None: items = []
    323         if (use_list is not None) or not _is_array(items):
--> 324             items = list(items) if use_list else _listify(items)
    325         if match is not None:
    326             if is_coll(match): match = len(match)

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/foundation.py in _listify(o)
    258     if isinstance(o, list): return o
    259     if isinstance(o, str) or _is_array(o): return [o]
--> 260     if is_iter(o): return list(o)
    261     return [o]
    262 

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastcore/foundation.py in __call__(self, *args, **kwargs)
    224             if isinstance(v,_Arg): kwargs[k] = args.pop(v.i)
    225         fargs = [args[x.i] if isinstance(x, _Arg) else x for x in self.pargs] + args[self.maxi+1:]
--> 226         return self.fn(*fargs, **kwargs)
    227 
    228 # Cell

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in _call_one(self, event_name)
    135     def _call_one(self, event_name):
    136         assert hasattr(event, event_name), event_name
--> 137         [cb(event_name) for cb in sort_by_run(self.cbs)]
    138 
    139     def _bn_bias_state(self, with_bias): return norm_bias_params(self.model, with_bias).map(self.opt.state)

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/learner.py in <listcomp>(.0)
    135     def _call_one(self, event_name):
    136         assert hasattr(event, event_name), event_name
--> 137         [cb(event_name) for cb in sort_by_run(self.cbs)]
    138 
    139     def _bn_bias_state(self, with_bias): return norm_bias_params(self.model, with_bias).map(self.opt.state)

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/callback/core.py in __call__(self, event_name)
     42                (self.run_valid and not getattr(self, 'training', False)))
     43         res = None
---> 44         if self.run and _run: res = getattr(self, event_name, noop)()
     45         if event_name=='after_fit': self.run=True #Reset self.run to True at each end of fit
     46         return res

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/callback/schedule.py in before_batch(self)
     84     def __init__(self, scheds): self.scheds = scheds
     85     def before_fit(self): self.hps = {p:[] for p in self.scheds.keys()}
---> 86     def before_batch(self): self._update_val(self.pct_train)
     87 
     88     def _update_val(self, pct):

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/callback/schedule.py in _update_val(self, pct)
     87 
     88     def _update_val(self, pct):
---> 89         for n,f in self.scheds.items(): self.opt.set_hyper(n, f(pct))
     90 
     91     def after_batch(self):

/local_disk0/.ephemeral_nfs/envs/pythonEnv-7d3b02f4-8c94-4299-8acc-1909d16e2085/lib/python3.7/site-packages/fastai/callback/schedule.py in _inner(pos)
     67         if pos == 1.: return scheds[-1](1.)
     68         idx = (pos >= pcts).nonzero().max()
---> 69         actual_pos = (pos-pcts[idx]) / (pcts[idx+1]-pcts[idx])
     70         return scheds[idx](actual_pos.item())
     71     return _inner

IndexError: index 3 is out of bounds for dimension 0 with size 3```

[MaxThone]

After reading the docs, perhaps it's better to report this in the FastAI forum