def __onep__(self):
""" called on new epoch. """
# history records
h = self.__hist__
# update the learning rate and suprimum of gradient
if h[-1]['terr'] < self.__einf__: # accelerate
self.lrt.set_value(self.lrt.get_value() * self.lrt_inc.get_value())
paint(self.nnt, self.__nnt0__)
self.__einf__ = h[-1]['terr']
else: # slow down
self.lrt.set_value(self.lrt.get_value() * self.lrt_dec.get_value())
paint(self.__nnt0__, self.nnt)
def __rest__(self, key=None):
""" restore a snap shot. """
key = -1 if key is None else key
ret, skp = self.__snap__[key], Snap.__skip__
for k, v in vars(self).iteritems():
if k in skp or callable(v) or k not in ret:
continue
if isinstance(v, TSV):
v.set_value(ret[k])
else:
v = ret[k]
paint(ret['nnt'], self.nnt)
# remove history after the snap shot
if '__hist__' in vars(self):
ep = ret['ep'].item()
del self.__hist__[ep + 1:]
return ret
def __shot__(self, key=None):
""" take a snap shot. """
key = -1 if key is None else key
if '__hist__' in vars(self) and len(self.__hist__) > 0:
ret = deepcopy(self.__hist__[-1])
else:
ret = dict()
skp = Snap.__skip__
for k, v in vars(self).iteritems():
if k in skp or callable(v) or k.startswith('__'):
continue
if isinstance(v, TSV):
ret[k] = v.get_value()
else:
ret[k] = deepcopy(v)
# ret.update(self.__hist__[-1])
ret['nnt'] = paint(self.nnt)
self.__snap__[key] = ret
return ret
def __init__(self, nnt, x=None, z=None, u=None, v=None, **kwd):
"""
Constructor.
: -------- parameters -------- :
nnt: an expression builder for the neural network to be trained,
could be a Nnt object.
x: the inputs, with the first dimension standing for sample units.
If unspecified, the trainer will try to evaluate the entry point and
cache the result as source data.
z: the labels, with the first dimension standing for sample units.
if unspecified, a simi-unsupervied training is assumed as the labels
will be identical to the inputs.
u: the valication data inputs
v: the validation data labels
: -------- kwd: keywords -------- :
-- bsz: size of a training batch
-- lrt: basic learning rate
-- lmb: weight decay factor, the lambda
-- err: expression builder for the computation of training error
between the network output {y} and the label {z}. the expression
must evaluate to a scalar.
-- reg: expression builder for the computation of weight panalize
the vector of parameters {w}, the expression must evaluate to a
scalar.
-- mmt: momentom of the trainer
-- vdr: validation disruption rate
"""
# numpy random number generator
seed = kwd.pop('seed', None)
nrng = kwd.pop('nrng', np.random.RandomState(seed))
from theano.tensor.shared_randomstreams import RandomStreams
trng = kwd.pop('trng', RandomStreams(nrng.randint(0x7FFFFFFF)))
# private members
self.__seed__ = seed
self.__nrng__ = nrng
self.__trng__ = trng
# expression of error and regulator terms
err = getattr(exb, kwd.get('err', 'CE'))
reg = getattr(exb, kwd.get('reg', 'L1'))
# the validation disruption
self.vdr = S(kwd.get('vdr'), 'VDR')
# current epoch index, use int64
self.ep = S(0, 'EP')
# training batch ppsize, use int64
bsz = kwd.get('bsz', 20)
self.bsz = S(bsz, 'BSZ')
# current batch index, use int64
self.bt = S(0, 'BT')
# momentumn, make sure momentum is a sane value
mmt = kwd.get('mmt', .0)
self.mmt = S(mmt, 'MMT')
# learning rate
lrt = kwd.get('lrt', .01)
lrt_inc = kwd.get('inc', 1.04)
lrt_dec = kwd.get('dec', 0.85)
self.lrt = S(lrt, 'LRT')
self.lrt_inc = S(lrt_inc, 'LRT_INC')
self.lrt_dec = S(lrt_dec, 'LRT_DEC')
# the raio of weight decay, lambda
lmd = kwd.get('lmd', .0)
self.lmd = S(lmd, 'LMD')
# the neural network
self.nnt = nnt
self.dim = (nnt.dim[0], nnt.dim[-1])
# supremum of gradient
self.gsup = S(.0)
# inputs and labels, for modeling and validation
x = S(np.zeros((bsz * 2, self.dim[0]), 'f') if x is None else x)
z = x if z is None else S(z)
u = x if u is None else S(u)
v = u if v is None else S(v)
self.x, self.z, self.u, self.v = x, z, u, v
# -------- construct trainer function -------- *
# 1) symbolic expressions
x = T.tensor(name='x', dtype=x.dtype, broadcastable=x.broadcastable)
z = T.tensor(name='z', dtype=z.dtype, broadcastable=z.broadcastable)
y = nnt(x) # expression of predicted output
# list of symbolic parameters to be tuned
pars = parms(y) # parameters
# list of symbolic weights to apply decay
vwgt = T.concatenate([p.flatten() for p in pars if p.name == 'w'])
# symbolic batch cost, which is the mean trainning erro over all
# observations and sub attributes.
# The observations are indexed by the first dimension of y and z, while
# the sub attributes are indexed by the rest but not last dimensions.
# The last dimension indices data points for each observation, examples
# are voxels in an MRI volume, and SNPs in a genome segment.
# Values of these data points are aggregated by the objective function,
# err, which can be L1, L2 norm and CE. the objective function return
# an scalar ratting of the training loss.
erro = err(y, z).mean()
# the sum of weights calculated for weight decay.
wsum = reg(vwgt)
cost = erro + wsum * self.lmd
l2er = exb.L2(y, z).mean()
# symbolic gradient of cost WRT parameters
grad = T.grad(cost, pars)
gabs = T.concatenate([T.abs_(g.flatten()) for g in grad])
gsup = T.max(gabs)
# trainer control
nwep = ((self.bt + 1) * self.bsz) // self.x.shape[-2] # new epoch?
# 2) define updates after each batch training
up = []
# update parameters using gradiant decent, and momentum
for p, g in zip(pars, grad):
# initialize accumulated gradient
# NOTE: p.eval() causes mehem!!
h = S(np.zeros_like(p.get_value()))
# accumulate gradient, partially historical (due to the momentum),
# partially noval
up.append((h, self.mmt * h + (1 - self.mmt) * g))
# update parameters by stepping down the accumulated gradient
up.append((p, p - self.lrt * h))
# update batch and eqoch index
up.append((self.bt, (self.bt + 1) * (1 - nwep)))
up.append((self.ep, self.ep + nwep))
# 3) the trainer functions
# expression of batch and whole data feed:
_ = T.arange((self.bt + 0) * self.bsz, (self.bt + 1) * self.bsz)
bts = {x: self.x.take(_, -2, 'wrap'), z: self.z.take(_, -2, 'wrap')}
dts = {x: self.x, z: self.z}
# each invocation sends one batch of training examples to the network,
# calculate total cost and tune the parameters by gradient decent.
self.step = F([], cost, name="step", givens=bts, updates=up)
# training error, training cost
self.terr = F([], erro, name="terr", givens=dts)
self.tcst = F([], cost, name="tcst", givens=dts)
# weights, and parameters
self.wsum = F([], wsum, name="wsum")
self.gsup = F([], gsup, name="gsup", givens=dts)
self.l2er = F([], l2er, name="l2er", givens=dts)
# * -------- done with trainer functions -------- *
# * -------- validation functions -------- *
# enable validation binary disruption (binary)?
if self.vdr:
_ = self.__trng__.binomial(self.v.shape, 1, self.vdr, dtype=FX)
vts = {x: self.u, z: (self.v + _) % C(2.0, FX)}
else:
vts = {x: self.u, z: self.v}
self.verr = F([], erro, name="verr", givens=vts)
# * ---------- logging and recording ---------- *
hd, rm = [], ['step', 'gavg', 'nwgt', 'berr', 'bcst']
for k, v in self.__dict__.items():
if k.startswith('__') or k in rm:
continue
if isinstance(v, type(self.lmd)) and v.ndim < 1:
hd.append((k, v.get_value))
if isinstance(v, type(self.bsz)) and v.ndim < 1:
hd.append((k, v.get_value))
if isinstance(v, type(self.step)):
hd.append((k, v))
self.__head__ = hd
self.__time__ = .0
# the first record
self.__hist__ = [self.__rpt__()]
self.__gsup__ = self.__hist__[0]['gsup']
self.__einf__ = self.__hist__[0]['terr']
self.__nnt0__ = paint(self.nnt)
# printing format
self.__pfmt__ = (
'{ep:04d}.{bt:03d}: {tcst:.2f} = {terr:.2f} + {lmd:.2e}*{wsum:.1f}'
'|{verr:.2f}, {l2er:.2f}|, {gsup:.2e}, {lrt:.2e}')
