def canonical(kernel):
'''Sorts a kernel tree into a canonical form.'''
if isinstance(kernel, fk.BaseKernel):
return kernel.copy()
elif isinstance(kernel, fk.MaskKernel):
return fk.MaskKernel(kernel.ndim, kernel.active_dimension,
canonical(kernel.base_kernel))
elif isinstance(kernel, fk.SumKernel):
new_ops = []
for op in kernel.operands:
op_canon = canonical(op)
if isinstance(op, fk.SumKernel):
new_ops += op_canon.operands
else:
new_ops.append(op_canon)
return fk.SumKernel(sorted(new_ops))
elif isinstance(kernel, fk.ProductKernel):
new_ops = []
for op in kernel.operands:
op_canon = canonical(op)
if isinstance(op, fk.ProductKernel):
new_ops += op_canon.operands
else:
new_ops.append(op_canon)
return fk.ProductKernel(sorted(new_ops))
else:
raise RuntimeError('Unknown kernel class:', kernel.__class__)
def polish_to_kernel(polish_expr):
if type(polish_expr) == tuple:
if polish_expr[0] == '+':
operands = [polish_to_kernel(e) for e in polish_expr[1:]]
return fk.SumKernel(operands)
elif polish_expr[0] == '*':
operands = [polish_to_kernel(e) for e in polish_expr[1:]]
return fk.ProductKernel(operands)
else:
raise RuntimeError('Unknown operator: %s' % polish_expr[0])
else:
assert isinstance(polish_expr, fk.Kernel)
return polish_expr
def expand(kernel, grammar):
result = expand_single_tree(kernel, grammar)
if isinstance(kernel, fk.BaseKernel):
pass
elif isinstance(kernel, fk.MaskKernel):
result += [
fk.MaskKernel(kernel.ndim, kernel.active_dimension, e)
for e in expand(kernel.base_kernel, grammar)
]
elif isinstance(kernel, fk.SumKernel):
for i, op in enumerate(kernel.operands):
for e in expand(op, grammar):
new_ops = kernel.operands[:i] + [e] + kernel.operands[i + 1:]
new_ops = [op.copy() for op in new_ops]
result.append(fk.SumKernel(new_ops))
elif isinstance(kernel, fk.ProductKernel):
for i, op in enumerate(kernel.operands):
for e in expand(op, grammar):
new_ops = kernel.operands[:i] + [e] + kernel.operands[i + 1:]
new_ops = [op.copy() for op in new_ops]
result.append(fk.ProductKernel(new_ops))
else:
raise RuntimeError('Unknown kernel class:', kernel.__class__)
return result