Make hnf_decomposition return the reduced HNF rather than the HNF.

Author: PierreQuinton

src/torchjd/sparse/_sparse_latticed_tensor.py

@@ -1,6 +1,6 @@
 import itertools
 import operator
-from collections.abc import Callable
+from collections.abc import Callable, Sequence
 from functools import wraps
 from itertools import accumulate
 from math import prod
@@ -14,7 +14,7 @@ class SparseLatticedTensor(Tensor):
     _HANDLED_FUNCTIONS = dict[Callable, Callable]()
 
     @staticmethod
-    def __new__(cls, physical: Tensor, basis: Tensor):
+    def __new__(cls, physical: Tensor, basis: Tensor, offset: Sequence[int], shape: Sequence[int]):
         assert basis.dtype == torch.int64
 
         # Note [Passing requires_grad=true tensors to subclasses]
@@ -27,13 +27,13 @@ def __new__(cls, physical: Tensor, basis: Tensor):
         # (which is bad!)
         assert not physical.requires_grad or not torch.is_grad_enabled()
 
-        pshape = tensor(physical.shape, dtype=torch.int64)
-        vshape = basis @ (pshape - 1) + 1
         return Tensor._make_wrapper_subclass(
-            cls, tuple(vshape.tolist()), dtype=physical.dtype, device=physical.device
+            cls, shape, dtype=physical.dtype, device=physical.device
         )
 
-    def __init__(self, physical: Tensor, basis: Tensor):
+    def __init__(
+        self, physical: Tensor, basis: Tensor, offset: Sequence[int], shape: Sequence[int]
+    ):
         """
         This constructor is made for specifying physical and basis exactly. It should not modify
         it.