def new_syn(tracing_mag=None):
syn = Synapse(n_axons=1)
syn.set_full_weights(np.array([[1]]))
if tracing_mag is not None:
syn.set_learning(tracing_mag=tracing_mag)
core.add_synapse(syn)
return syn
def build_connection(model, conn):
if nengo_transforms is not None:
if isinstance(conn.transform, nengo_transforms.Convolution):
# TODO: integrate these into the same function
conv.build_conv2d_connection(model, conn)
return
elif not isinstance(conn.transform, nengo_transforms.Dense):
raise NotImplementedError(
"nengo-loihi does not yet support %s transforms"
% conn.transform)
# Create random number generator
rng = np.random.RandomState(model.seeds[conn])
pre_cx = model.objs[conn.pre_obj]['out']
post_cx = model.objs[conn.post_obj]['in']
assert isinstance(pre_cx, (LoihiBlock, LoihiInput))
assert isinstance(post_cx, (LoihiBlock, Probe))
weights = None
eval_points = None
solver_info = None
neuron_type = None
post_slice = conn.post_slice
# sample transform (if using a distribution)
transform = sample_transform(conn, rng=rng)
tau_s = 0.0 # `synapse is None` gets mapped to `tau_s = 0.0`
if isinstance(conn.synapse, nengo.synapses.Lowpass):
tau_s = conn.synapse.tau
elif conn.synapse is not None:
raise NotImplementedError("Cannot handle non-Lowpass synapses")
needs_decode_neurons = False
target_encoders = None
if isinstance(conn.pre_obj, Node):
assert conn.pre_slice == slice(None)
if np.array_equal(transform, np.array(1.)):
# TODO: this identity transform may be avoidable
transform = np.eye(conn.pre.size_out)
else:
assert transform.ndim == 2, "transform shape not handled yet"
assert transform.shape[1] == conn.pre.size_out
assert transform.shape[1] == conn.pre.size_out
if isinstance(conn.pre_obj, ChipReceiveNeurons):
weights = transform / model.dt
neuron_type = conn.pre_obj.neuron_type
else:
# input is on-off neuron encoded, so double/flip transform
weights = np.column_stack([transform, -transform])
target_encoders = 'node_encoders'
elif (isinstance(conn.pre_obj, Ensemble)
and isinstance(conn.pre_obj.neuron_type, nengo.Direct)):
raise NotImplementedError()
elif isinstance(conn.pre_obj, Ensemble): # Normal decoded connection
eval_points, decoders, solver_info = model.build(
conn.solver, conn, rng, transform)
if conn.solver.weights and not conn.solver.compositional:
weights = decoders
else:
weights = multiply(transform, decoders)
# the decoder solver assumes a spike height of 1/dt; that isn't the
# case on loihi, so we need to undo that scaling
weights = weights / model.dt
neuron_type = conn.pre_obj.neuron_type
if conn.solver.weights:
# weight solvers only allowed on ensemble->ensemble connections
assert isinstance(conn.post_obj, Ensemble)
if conn.solver.compositional:
encoders = model.params[conn.post_obj].scaled_encoders.T
encoders = encoders[post_slice]
weights = multiply(encoders.T, weights)
# post slice already applied to encoders (either here or in
# `build_decoders`), so don't apply later
post_slice = None
else:
needs_decode_neurons = True
elif isinstance(conn.pre_obj, Neurons):
assert conn.pre_slice == slice(None)
assert transform.ndim == 2, "transform shape not handled yet"
weights = transform / model.dt
neuron_type = conn.pre_obj.ensemble.neuron_type
else:
raise NotImplementedError("Connection from type %r" % (
type(conn.pre_obj),))
if neuron_type is not None and hasattr(neuron_type, 'amplitude'):
weights = weights * neuron_type.amplitude
mid_cx = pre_cx
mid_axon_inds = None
post_tau = tau_s
if needs_decode_neurons and not isinstance(conn.post_obj, Neurons):
# --- add decode neurons
assert weights.ndim == 2
d, n = weights.shape
if isinstance(post_cx, Probe):
# use non-spiking decode neurons for voltage probing
assert post_cx.target is None
assert post_slice == slice(None)
# use the same scaling as the ensemble does, to get good
# decodes. Note that this assumes that the decoded value
# is in the range -radius to radius, which is usually true.
weights = weights / conn.pre_obj.radius
gain = 1
dec_cx = LoihiBlock(2 * d, label='%s' % conn)
dec_cx.compartment.configure_nonspiking(
dt=model.dt, vth=model.vth_nonspiking)
dec_cx.compartment.bias[:] = 0
model.add_block(dec_cx)
model.objs[conn]['decoded'] = dec_cx
dec_syn = Synapse(n, label="probe_decoders")
weights2 = gain * np.vstack([weights, -weights]).T
dec_syn.set_full_weights(weights2)
dec_cx.add_synapse(dec_syn)
model.objs[conn]['decoders'] = dec_syn
else:
# use spiking decode neurons for on-chip connection
if isinstance(conn.post_obj, Ensemble):
# loihi encoders don't include radius, so handle scaling here
weights = weights / conn.post_obj.radius
post_d = conn.post_obj.size_in
post_inds = np.arange(post_d, dtype=np.int32)[post_slice]
assert weights.shape[0] == len(post_inds) == conn.size_out == d
mid_axon_inds = model.decode_neurons.get_post_inds(
post_inds, post_d)
target_encoders = 'decode_neuron_encoders'
dec_cx, dec_syn = model.decode_neurons.get_block(
weights, block_label="%s" % conn, syn_label="decoders")
model.add_block(dec_cx)
model.objs[conn]['decoded'] = dec_cx
model.objs[conn]['decoders'] = dec_syn
# use tau_s for filter into decode neurons, decode_tau for filter out
dec_cx.compartment.configure_filter(tau_s, dt=model.dt)
post_tau = model.decode_tau
dec_ax0 = Axon(n, label="decoders")
dec_ax0.target = dec_syn
pre_cx.add_axon(dec_ax0)
model.objs[conn]['decode_axon'] = dec_ax0
if conn.learning_rule_type is not None:
rule_type = conn.learning_rule_type
if isinstance(rule_type, nengo.PES):
if not isinstance(rule_type.pre_synapse,
nengo.synapses.Lowpass):
raise ValidationError(
"Loihi only supports `Lowpass` pre-synapses for "
"learning rules", attr='pre_synapse', obj=rule_type)
tracing_tau = rule_type.pre_synapse.tau / model.dt
# Nengo builder scales PES learning rate by `dt / n_neurons`
n_neurons = (conn.pre_obj.n_neurons
if isinstance(conn.pre_obj, Ensemble)
else conn.pre_obj.size_in)
learning_rate = rule_type.learning_rate * model.dt / n_neurons
# Account for scaling to put integer error in range [-127, 127]
learning_rate /= model.pes_error_scale
# Tracing mag set so that the magnitude of the pre trace
# is independent of the pre tau. `dt` factor accounts for
# Nengo's `dt` spike scaling. Where is the second `dt` from?
# Maybe the fact that post decode neurons have `vth = 1/dt`?
tracing_mag = -np.expm1(-1. / tracing_tau) / model.dt**2
# learning weight exponent controls the maximum weight
# magnitude/weight resolution
wgt_exp = model.pes_wgt_exp
dec_syn.set_learning(
learning_rate=learning_rate,
tracing_mag=tracing_mag,
tracing_tau=tracing_tau,
wgt_exp=wgt_exp,
)
else:
raise NotImplementedError()
mid_cx = dec_cx
if isinstance(post_cx, Probe):
assert post_cx.target is None
assert post_slice == slice(None)
post_cx.target = mid_cx
mid_cx.add_probe(post_cx)
elif isinstance(conn.post_obj, Neurons):
assert isinstance(post_cx, LoihiBlock)
assert post_slice == slice(None)
if weights is None:
raise NotImplementedError("Need weights for connection to neurons")
else:
assert weights.ndim == 2
n2, n1 = weights.shape
assert post_cx.n_neurons == n2
syn = Synapse(n1, label="neuron_weights")
gain = model.params[conn.post_obj.ensemble].gain
syn.set_full_weights(weights.T * gain)
post_cx.add_synapse(syn)
model.objs[conn]['weights'] = syn
ax = Axon(mid_cx.n_neurons, label="neuron_weights")
ax.target = syn
mid_cx.add_axon(ax)
post_cx.compartment.configure_filter(post_tau, dt=model.dt)
if conn.learning_rule_type is not None:
raise NotImplementedError()
elif isinstance(conn.post_obj, Ensemble) and conn.solver.weights:
assert isinstance(post_cx, LoihiBlock)
assert weights.ndim == 2
n2, n1 = weights.shape
assert post_cx.n_neurons == n2
# loihi encoders don't include radius, so handle scaling here
weights = weights / conn.post_obj.radius
syn = Synapse(n1, label="%s::decoder_weights" % conn)
syn.set_full_weights(weights.T)
post_cx.add_synapse(syn)
model.objs[conn]['weights'] = syn
ax = Axon(n1, label="decoder_weights")
ax.target = syn
mid_cx.add_axon(ax)
post_cx.compartment.configure_filter(post_tau, dt=model.dt)
if conn.learning_rule_type is not None:
raise NotImplementedError()
elif isinstance(conn.post_obj, Ensemble):
assert target_encoders is not None
if target_encoders not in post_cx.named_synapses:
build_decode_neuron_encoders(
model, conn.post_obj, kind=target_encoders)
mid_ax = Axon(mid_cx.n_neurons, label="encoders")
mid_ax.target = post_cx.named_synapses[target_encoders]
mid_ax.set_axon_map(mid_axon_inds)
mid_cx.add_axon(mid_ax)
model.objs[conn]['mid_axon'] = mid_ax
post_cx.compartment.configure_filter(post_tau, dt=model.dt)
else:
# This includes Node, since nodes can't be targets on-chip
raise NotImplementedError()
model.params[conn] = BuiltConnection(
eval_points=eval_points,
solver_info=solver_info,
transform=transform,
weights=weights)
def build_full_chip_connection(model, conn): # noqa: C901
"""Build dense or sparse connections on-chip"""
# Create random number generator
rng = np.random.RandomState(model.seeds[conn])
pre_obj = model.objs[conn.pre_obj]["out"]
post_obj = model.objs[conn.post_obj]["in"]
assert isinstance(pre_obj, (LoihiBlock, LoihiInput))
assert isinstance(post_obj, (LoihiBlock, LoihiProbe))
weights = None
eval_points = None
solver_info = None
neuron_type = None
pre_slice = conn.pre_slice
post_slice = conn.post_slice
# sample transform (if using a distribution), transform shape (out, in)
transform = sample_transform(conn, rng=rng)
tau_s = 0.0 # `synapse is None` gets mapped to `tau_s = 0.0`
if isinstance(conn.synapse, nengo.synapses.Lowpass):
tau_s = conn.synapse.tau
elif conn.synapse is not None:
raise NotImplementedError("Cannot handle non-Lowpass synapses")
needs_decode_neurons = False
target_encoders = None
is_chip_process = isinstance(conn.pre_obj, Node) and isinstance(
conn.pre_obj.output, ChipProcess
)
if isinstance(conn.pre_obj, Node) and not (
isinstance(conn.pre_obj, ChipReceiveNeurons) or is_chip_process
):
assert conn.pre_slice == slice(None)
weights = expand_matrix(transform, shape=(conn.post.size_in, conn.pre.size_out))
# input is on-off neuron encoded, so double/flip transform
weights = stack_matrices([weights, scale_matrix(weights, -1)], order="h")
target_encoders = "node_encoders"
elif isinstance(conn.pre_obj, Ensemble) and isinstance(
conn.pre_obj.neuron_type, nengo.Direct
):
raise NotImplementedError()
elif isinstance(conn.pre_obj, Ensemble): # Normal decoded connection
if isinstance(transform, scipy.sparse.spmatrix):
raise BuildError(
"Applying a sparse transform to a decoded connection is not supported"
)
eval_points, decoders, solver_info = model.build(
conn.solver, conn, rng, transform
)
pre_slice = slice(None) # taken care of in decoders
if conn.solver.weights and not conn.solver.compositional:
weights = decoders
else:
weights = multiply(transform, decoders)
# the decoder solver assumes a spike height of 1/dt; that isn't the
# case on loihi, so we need to undo that scaling
weights = scale_matrix(weights, 1.0 / model.dt)
neuron_type = conn.pre_obj.neuron_type
if conn.solver.weights:
# weight solvers only allowed on ensemble->ensemble connections
assert isinstance(conn.post_obj, Ensemble)
if conn.solver.compositional:
encoders = model.params[conn.post_obj].scaled_encoders
weights = multiply(encoders[:, post_slice], weights)
# post slice already applied to encoders (either here or in
# `build_decoders`), so don't apply later
post_slice = slice(None)
else:
needs_decode_neurons = True
elif isinstance(conn.pre_obj, (Neurons, ChipReceiveNeurons)) or is_chip_process:
weights = expand_matrix(transform, shape=(conn.post.size_in, conn.pre.size_out))
weights = scale_matrix(weights, 1.0 / model.dt)
neuron_type = (
None
if is_chip_process
else conn.pre_obj.neuron_type
if isinstance(conn.pre_obj, ChipReceiveNeurons)
else conn.pre_obj.ensemble.neuron_type
)
if isinstance(conn.post_obj, Ensemble):
needs_decode_neurons = True
else:
raise NotImplementedError("Connection from type %r" % (type(conn.pre_obj),))
if neuron_type is not None and hasattr(neuron_type, "amplitude"):
weights = scale_matrix(weights, neuron_type.amplitude)
# to proper dtype
transform = transform.astype(nengo.rc.float_dtype)
weights = weights.astype(nengo.rc.float_dtype)
# loihi_weights has shape (in, out), to match the shape by block.Synapses
loihi_weights = weights.T
mid_obj = pre_obj
mid_axon_inds = None
post_tau = tau_s
if needs_decode_neurons and not isinstance(conn.post_obj, Neurons):
# --- add decode neurons
assert weights.ndim == 2
n, d = loihi_weights.shape
if isinstance(post_obj, LoihiProbe):
# use non-spiking decode neurons for voltage probing
assert len(post_obj.target) == 0 or post_obj.target == [None]
assert post_slice == slice(None)
# use the same scaling as the ensemble does, to get good
# decodes. Note that this assumes that the decoded value
# is in the range -radius to radius, which is usually true.
gain = np.array(1.0 / conn.pre_obj.radius, dtype=nengo.rc.float_dtype)
decoder_block = LoihiBlock(2 * d, label="%s" % conn)
decoder_block.compartment.configure_nonspiking(
dt=model.dt, vth=model.vth_nonspiking
)
decoder_block.compartment.bias[:] = 0
dec_syn = Synapse(n, label="probe_decoders")
weights2 = stack_matrices(
[scale_matrix(loihi_weights, gain), scale_matrix(loihi_weights, -gain)],
order="h",
)
dec_syn.set_weights(weights2)
decoder_block.add_synapse(dec_syn)
else:
# use spiking decode neurons for on-chip connection
if isinstance(conn.post_obj, Ensemble):
# loihi encoders don't include radius, so handle scaling here
gain = np.array(1.0 / conn.post_obj.radius, dtype=nengo.rc.float_dtype)
loihi_weights = scale_matrix(loihi_weights, gain)
post_d = conn.post_obj.size_in
post_inds = np.arange(post_d, dtype=np.int32)[post_slice]
assert loihi_weights.shape[1] == len(post_inds) == conn.size_out
mid_axon_inds = model.decode_neurons.get_post_inds(post_inds, post_d)
target_encoders = "decode_neuron_encoders"
decoder_block, dec_syn = model.decode_neurons.get_block(
loihi_weights, block_label="%s" % conn, syn_label="decoders"
)
model.add_block(decoder_block)
model.objs[conn]["decoded"] = decoder_block
model.objs[conn]["decoders"] = dec_syn
model.connection_decode_neurons[conn] = decoder_block
# use tau_s for filter into decode neurons, decode_tau for filter out
decoder_block.compartment.configure_filter(tau_s, dt=model.dt)
post_tau = model.decode_tau
target_axons = -np.ones(pre_obj.n_neurons, dtype=np.int32)
target_axons[pre_slice] = np.arange(target_axons[pre_slice].size)
pre_slice = slice(None)
dec_ax0 = Axon(n, label="decoders")
dec_ax0.target = dec_syn
dec_ax0.set_compartment_axon_map(target_axons)
pre_obj.add_axon(dec_ax0)
model.objs[conn]["decode_axon"] = dec_ax0
loihi_weights = None # weights have now been handled
if conn.learning_rule_type is not None:
rule_type = conn.learning_rule_type
if isinstance(rule_type, nengo.PES):
if not isinstance(rule_type.pre_synapse, nengo.synapses.Lowpass):
raise ValidationError(
"Loihi only supports `Lowpass` pre-synapses for learning rules",
attr="pre_synapse",
obj=rule_type,
)
pre_tau = rule_type.pre_synapse.tau
float_tracing_tau = pre_tau / model.dt
tracing_tau = int(round(float_tracing_tau))
if not np.allclose(float_tracing_tau, tracing_tau):
warnings.warn(
f"PES learning rule `pre_synapse.tau` ({pre_tau}) is not an "
f"integer multiple of `dt` ({model.dt}). Rounding."
)
# Nengo builder scales PES learning rate by `dt / n_neurons`
n_neurons = (
conn.pre_obj.n_neurons
if isinstance(conn.pre_obj, Ensemble)
else conn.pre_obj.size_in
)
learning_rate = rule_type.learning_rate * model.dt / n_neurons
# Account for scaling to put integer error in range [-127, 127]
learning_rate /= model.pes_error_scale
# Tracing mag set so that the magnitude of the pre trace
# is independent of the pre tau. `dt` factor accounts for
# Nengo's `dt` spike scaling. Where is the second `dt` from?
# Maybe the fact that post decode neurons have `vth = 1/dt`?
tracing_mag = -np.expm1(-1.0 / tracing_tau) / model.dt**2
# learning weight exponent controls the maximum weight
# magnitude/weight resolution
wgt_exp = model.pes_wgt_exp
dec_syn.set_learning(
learning_rate=learning_rate,
tracing_mag=tracing_mag,
tracing_tau=tracing_tau,
wgt_exp=wgt_exp,
)
else:
raise NotImplementedError()
mid_obj = decoder_block
if isinstance(post_obj, LoihiProbe):
assert post_obj.target == [None]
assert post_slice == slice(None)
post_obj.target[0] = mid_obj
model.add_probe(post_obj)
elif isinstance(conn.post_obj, Neurons):
assert isinstance(post_obj, LoihiBlock)
assert post_slice == slice(None)
if loihi_weights is None:
raise NotImplementedError("Need weights for connection to neurons")
assert loihi_weights.ndim == 2
n1, n2 = loihi_weights.shape
assert post_obj.n_neurons == n2
syn = Synapse(n1, label="neuron_weights")
gain = model.params[conn.post_obj.ensemble].gain
loihi_weights = scale_matrix(loihi_weights, gain)
syn.set_weights(loihi_weights)
post_obj.add_synapse(syn)
model.objs[conn]["weights"] = syn
target_axons = -np.ones(mid_obj.n_neurons, dtype=np.int32)
target_axons[pre_slice] = np.arange(target_axons[pre_slice].size)
assert target_axons[pre_slice].size == n1
ax = Axon(mid_obj.n_neurons, label="neuron_weights")
ax.target = syn
ax.set_compartment_axon_map(target_axons)
mid_obj.add_axon(ax)
post_obj.compartment.configure_filter(post_tau, dt=model.dt)
if conn.learning_rule_type is not None:
raise NotImplementedError()
elif isinstance(conn.post_obj, Ensemble) and conn.solver.weights:
assert isinstance(post_obj, LoihiBlock)
assert pre_slice == slice(None), "Not implemented"
assert post_slice == slice(None)
assert loihi_weights.ndim == 2
n1, n2 = loihi_weights.shape
assert post_obj.n_neurons == n2
# loihi encoders don't include radius, so handle scaling here
scale = np.array(1.0 / conn.post_obj.radius, dtype=nengo.rc.float_dtype)
loihi_weights = scale_matrix(loihi_weights, scale)
syn = Synapse(n1, label="%s::decoder_weights" % conn)
syn.set_weights(loihi_weights)
post_obj.add_synapse(syn)
model.objs[conn]["weights"] = syn
ax = Axon(n1, label="decoder_weights")
ax.target = syn
mid_obj.add_axon(ax)
post_obj.compartment.configure_filter(post_tau, dt=model.dt)
if conn.learning_rule_type is not None:
raise NotImplementedError()
elif isinstance(conn.post_obj, Ensemble):
assert isinstance(post_obj, LoihiBlock)
assert pre_slice == slice(None), "Not implemented"
assert post_slice == slice(None)
assert target_encoders is not None
if target_encoders not in post_obj.named_synapses:
build_decode_neuron_encoders(model, conn.post_obj, kind=target_encoders)
mid_ax = Axon(mid_obj.n_neurons, label="encoders")
mid_ax.target = post_obj.named_synapses[target_encoders]
mid_ax.set_compartment_axon_map(mid_axon_inds)
mid_obj.add_axon(mid_ax)
model.objs[conn]["mid_axon"] = mid_ax
post_obj.compartment.configure_filter(post_tau, dt=model.dt)
else:
# This includes Node, since nodes can't be targets on-chip
raise NotImplementedError()
model.params[conn] = BuiltConnection(
eval_points=eval_points,
solver_info=solver_info,
transform=transform, # sampled transform
weights=weights, # scaled weights (including decoders)
)
