diff --git a/pyscf_ipu/nanoDFT/compute_eri_utils.py b/pyscf_ipu/nanoDFT/compute_eri_utils.py
index 921d111..e63717c 100644
--- a/pyscf_ipu/nanoDFT/compute_eri_utils.py
+++ b/pyscf_ipu/nanoDFT/compute_eri_utils.py
@@ -147,11 +147,20 @@ def prepare_integrals_2_inputs(mol):
 
     
     screened_indices_s8_4d = []
+    tolerance = 1e-7
     
-    # sample complete column as pattern seed
+    # sample symmetry pattern and do safety check
     ERI = mol.intor('int2e_sph')
-    nonzero_seed = ERI[N-1, N-1, :, 0] != 0
-    tolerance = 1e-7
+    if N % 2 == 0:
+        nonzero_seed = ERI[N-1, N-1, :N//2, 0] != 0
+        nonzero_seed = np.concatenate([nonzero_seed, np.flip(nonzero_seed)])
+    else:
+        nonzero_seed = ERI[N-1, N-1, :(N+1)//2, 0] != 0
+        nonzero_seed = np.concatenate([nonzero_seed, np.flip(nonzero_seed[:-1])])
+    if not np.equal(nonzero_seed, ERI[N-1, N-1, :, 0]).all():
+        print('# -------------------------------------------------------------- #')
+        print('# WARNING: Experimental symmetry pattern sample is inconsistent. #')
+        print('# -------------------------------------------------------------- #')
 
     # print('test:')
     # for k in range(N):
@@ -191,6 +200,9 @@ def prepare_integrals_2_inputs(mol):
             if ok:
                 screened_indices_s8_4d.append((d, c, b, a))
 
+    print('n_bas', n_bas)
+    print('ao_loc', ao_loc)
+
     # Fill input_ijkl and output_sizes with the necessary indices.
     c = 0
     for i in range(n_bas):