update NAS-Bench-201 API to support str2structure

lib/nas_201_api/api.py

@@ -251,6 +251,26 @@ class NASBench201API(object):
       else:
         print('This index ({:}) is out of range (0~{:}).'.format(index, len(self.meta_archs)))
 
+  # This func shows how to read the string0based architecture encoding
+  #   the same as the `str2structure` func in `AutoDL-Projects/lib/models/cell_searchs/genotypes.py`
+  # Usage:
+  #   arch = api.str2structure( '|nor_conv_1x1~0|+|none~0|none~1|+|none~0|none~1|skip_connect~2|' )
+  #   print ('there are {:} nodes in this arch'.format(len(arch)+1)) # arch is a list
+  #   for i, node in enumerate(arch):
+  #     print('the {:}-th node is the sum of these {:} nodes with op: {:}'.format(i+1, len(node), node))
+  @staticmethod
+  def str2structure(xstr):
+    assert isinstance(xstr, str), 'must take string (not {:}) as input'.format(type(xstr))
+    nodestrs = xstr.split('+')
+    genotypes = []
+    for i, node_str in enumerate(nodestrs):
+      inputs = list(filter(lambda x: x != '', node_str.split('|')))
+      for xinput in inputs: assert len(xinput.split('~')) == 2, 'invalid input length : {:}'.format(xinput)
+      inputs = ( xi.split('~') for xi in inputs )
+      input_infos = tuple( (op, int(IDX)) for (op, IDX) in inputs)
+      genotypes.append( input_infos )
+    return genotypes
+
 
 
 class ArchResults(object):