Numba Cholesky: Allow inplace on C_contiguous inputs

Author: ricardoV94

pytensor/link/numba/dispatch/linalg/decomposition/cholesky.py

@@ -29,21 +29,27 @@ def cholesky_impl(A, lower=0, overwrite_a=False, check_finite=True):
     w_type = _get_underlying_float(dtype)
     numba_potrf = _LAPACK().numba_xpotrf(dtype)
 
-    def impl(A, lower=0, overwrite_a=False, check_finite=True):
+    def impl(A, lower=False, overwrite_a=False, check_finite=True):
         _N = np.int32(A.shape[-1])
         if A.shape[-2] != _N:
             raise linalg.LinAlgError("Last 2 dimensions of A must be square")
 
-        UPLO = val_to_int_ptr(ord("L") if lower else ord("U"))
-        N = val_to_int_ptr(_N)
-        LDA = val_to_int_ptr(_N)
-        INFO = val_to_int_ptr(0)
-
+        transposed = False
         if overwrite_a and A.flags.f_contiguous:
             A_copy = A
+        elif overwrite_a and A.flags.c_contiguous:
+            # We can work on the transpose of A directly
+            A_copy = A.T
+            transposed = True
+            lower = not lower
         else:
             A_copy = _copy_to_fortran_order(A)
 
+        UPLO = val_to_int_ptr(ord("L") if lower else ord("U"))
+        N = val_to_int_ptr(_N)
+        LDA = val_to_int_ptr(_N)
+        INFO = val_to_int_ptr(0)
+
         numba_potrf(
             UPLO,
             N,
@@ -61,6 +67,10 @@ def impl(A, lower=0, overwrite_a=False, check_finite=True):
                 for i in range(j + 1, _N):
                     A_copy[i, j] = 0.0
 
-        return A_copy, int_ptr_to_val(INFO)
+        info_int = int_ptr_to_val(INFO)
+
+        if transposed:
+            return A_copy.T, info_int
+        return A_copy, info_int
 
     return impl

tests/link/numba/test_slinalg.py

@@ -449,8 +449,8 @@ def test_cholesky(lower: bool, overwrite_a: bool):
     val_c_contig = np.copy(val, order="C")
     res_c_contig = fn(val_c_contig)
     np.testing.assert_allclose(res_c_contig, res)
-    # Cannot destroy C-contiguous input
-    np.testing.assert_allclose(val_c_contig, val)
+    # Should always be destroyable
+    assert (val == val_c_contig).all() == (not overwrite_a)
 
     # Test non-contiguous input
     val_not_contig = np.repeat(val, 2, axis=0)[::2]