diff --git a/qtensor/contraction_backends/torch.py b/qtensor/contraction_backends/torch.py
index c90c3165..0074c1e9 100644
--- a/qtensor/contraction_backends/torch.py
+++ b/qtensor/contraction_backends/torch.py
@@ -228,18 +228,20 @@ def get_result_data(self, result):
 
 class TorchBackendMatm(TorchBackend):
 
-    def _get_index_sizes(self, *ixs):
+    def _get_index_sizes(self, *ixs, size_dict = None):
+        if size_dict is not None:
+            return [size_dict[i] for i in ixs]
         try:
             sizes = [ i.size for i in ixs ]
         except AttributeError:
             sizes = [2] * len(ixs)
         return sizes
 
-    def _get_index_space_size(self, *ixs):
-        sizes = self._get_index_sizes(*ixs)
+    def _get_index_space_size(self, *ixs, size_dict = None):
+        sizes = self._get_index_sizes(*ixs, size_dict = size_dict)
         return reduce(np.multiply, sizes, 1)
 
-    def pairwise_sum_contract(self, ixa, a, ixb, b, ixout):
+    def pairwise_sum_contract(self, ixa, a, ixb, b, ixout, size_dict = None):
         out = ixout
         common = set(ixa).intersection(set(ixb))
         # -- sum indices that are in one tensor only
@@ -267,16 +269,18 @@ def pairwise_sum_contract(self, ixa, a, ixb, b, ixout):
         kix = common - set(out)
         fix = common - kix
         common = list(kix) + list(fix)
-        #print(f'{ixa=} {ixb=} {ixout=}; {common=} {mix=} {nix=}')
-        a = tensors[0].permute(*[
-            list(ixs[0]).index(x) for x in common + list(mix)
-        ])
-
-        b = tensors[1].permute(*[
-            list(ixs[1]).index(x) for x in common + list(nix)
-        ])
-
-        k, f, m, n = [self._get_index_space_size(*ix)
+        #print(f'{ixa=} {ixb=} {ixout=}; {common=} {mix=} {nix=}, {size_dict=}')
+        if tensors[0].numel() > 1:
+            a = tensors[0].permute(*[
+                list(ixs[0]).index(x) for x in common + list(mix)
+            ])
+
+        if tensors[1].numel() > 1:
+            b = tensors[1].permute(*[
+                list(ixs[1]).index(x) for x in common + list(nix)
+            ])
+
+        k, f, m, n = [self._get_index_space_size(*ix, size_dict=size_dict)
                       for ix in (kix, fix, mix, nix)
                      ]
         a = a.reshape(k, f, m)
@@ -284,12 +288,15 @@ def pairwise_sum_contract(self, ixa, a, ixb, b, ixout):
         c = torch.einsum('kfm, kfn -> fmn', a, b)
         if len(out):
             #print('out ix', out, 'kfmnix', kix, fix, mix, nix)
-            c = c.reshape(*self._get_index_sizes(*out))
+            c = c.reshape(*self._get_index_sizes(*out, size_dict=size_dict))
         #print('outix', out, 'res', c.shape, 'kfmn',kix, fix, mix, nix)
 
         current_ord_ = list(fix) + list(mix) + list(nix)
         if len(out):
             c = c.permute(*[current_ord_.index(i) for i in out])
+        else:
+            c = c.flatten()
+        #print(f'c shape {c.shape}')
         return c
 
     def process_bucket(self, bucket, no_sum=False):
@@ -303,17 +310,24 @@ def process_bucket(self, bucket, no_sum=False):
 
             ixr = list(map(int, result_indices))
             ixt = list(map(int, tensor.indices))
-            result_indices = tuple(sorted(
+            out_indices = tuple(sorted(
                 set(result_indices + tensor.indices),
                 key=int, reverse=True
             )
             )
-            ixout = list(map(int, result_indices))
-
-            logger.trace('Before contract. expr: {}, {} ->', ixr, ixt, ixout)
-            result_data_new = self.pairwise_sum_contract(ixr, result_data, ixt, tensor.data, ixout)
+            ixout = list(map(int, out_indices))
+
+            logger.trace('Before contract. expr: {}, {} -> {}', ixr, ixt, ixout)
+            size_dict = {}
+            for i in result_indices:
+                size_dict[int(i)] = i.size
+            for i in tensor.indices:
+                size_dict[int(i)] = i.size
+            logger.debug("result_indices: {}", result_indices)
+            result_data_new = self.pairwise_sum_contract(ixr, result_data, ixt, tensor.data, ixout, size_dict = size_dict)
+            result_indices = out_indices
             #result_data = torch.einsum(expr, result_data, tensor.data)
-            logger.trace("Data: {}, -> {}", result_data, tensor.data, result_data_new)
+            logger.trace("Data: {}, {} -> {}", result_data.shape, tensor.data.shape, result_data_new.shape)
             result_data = result_data_new
 
             # Merge and sort indices and shapes
@@ -334,10 +348,24 @@ def process_bucket(self, bucket, no_sum=False):
             ))[:-1]
             ixout = list(map(int, result_indices))
 
-            logger.trace('Before contract. expr: {}, {} ->', ixr, ixt, ixout)
-            result_data_new = self.pairwise_sum_contract(ixr, result_data, ixt, tensor.data, ixout)
+            logger.trace('Before contract. expr: {}, {} -> {}', ixr, ixt, ixout)
+            size_dict = {}
+            for i in result_indices:
+                size_dict[int(i)] = i.size
+            for i in tensor.indices:
+                size_dict[int(i)] = i.size
+            #logger.debug("result_indices: {}", result_indices)
+            result_data_new = self.pairwise_sum_contract(ixr, result_data, ixt, tensor.data, ixout, size_dict = size_dict)
             #result_data = torch.einsum(expr, result_data, tensor.data)
-            logger.trace("Data: {}, -> {}", result_data, tensor.data, result_data_new)
+            logger.trace("Data: {}, {} -> {}", result_data.mean(), tensor.data.mean(), result_data_new.mean())
+            #if result_data_new.mean() == 0:
+            #    logger.warning("Result is zero")
+            #    logger.debug("result_indices: {}", result_indices)
+            #    logger.debug("result_data: {}", result_data)
+            #    logger.debug("tensor: {}", tensor)
+            #    logger.debug("tensor_data: {}", tensor.data)
+            #    logger.debug("result_data_new: {}", result_data_new)
+            #    raise ValueError("Result is zero")
             result_data = result_data_new
         else:
             result_data = result_data.sum(axis=-1)