Originally posted by **AndreaBraschi** September 13, 2023
Hi all,
I've written a function to concatenate 2 square `LinearOperator` objects with different shapes:
```
from linear_operator.operators import ZeroLinearOperator, CatLinearOperator, KroneckerProductLinearOperator
def cat_LinearOperators(*linear_operators):
oper_A = linear_operators[0]
oper_B = linear_operators[1]
oper_A_size = oper_A.shape[0]
oper_B_size = oper_B.shape[0]
# mat_A
a = ZeroLinearOperator(oper_A_size, oper_B_size)
cat_1 =CatLinearOperator(a, oper_A, dim=1)
c = ZeroLinearOperator(oper_B_size, oper_B_size)
cat_2 = CatLinearOperator(a.transpose(-1, -2), c, dim=1)
tensor_A = CatLinearOperator(cat_2, cat_1, dim=0)
# mat_B
e = ZeroLinearOperator(oper_B_size, oper_A_size)
cat_3 = CatLinearOperator(oper_B, e, dim=1)
c = ZeroLinearOperator(oper_A_size, lazy_A_size)
cat_4 = CatLinearOperator(c, e, dim=0)
tensor_B = CatLinearOperator(cat_3, cat_4.transpose(-1, -2), dim=0)
cat_operator = SumLinearOperator(tensor_A, tensor_B)
return cat_operator
```
the function works, butI get the following `RuntimeError` when I evaluate the resulting `CatLinearOperator`:
`Representation of a LazyTensor should consist only of Tensors`.
You can evaluate the function yourself:
```
tensor_A = torch.randn(38, 38)
tensor_B = torch.randn(50, 50)
tensor_C = torch.randn(4, 4)
Kron_A = KroneckerProductLinearOperator(tensor_A, tensor_B)
Kron_B = KroneckerProductLinearOperator(tensor_C, tensor_B)
cat_operator =cat_LinearOperators(Kron_B, Kron_A)
cat_operator.to_dense()
```
I start to believe that the mistake is in how I use the `ZeroLinearOperator` object?
Any help or suggestion will be greatly appreciated.
Many thanks,
Andrea
Discussed in https://github.com/cornellius-gp/linear_operator/discussions/78