[GitHub] taliesinb commented on issue #12760: Extremely weird shape inference bug in foreach

[GitBox <gi...@apache.org>]

taliesinb commented on issue #12760: Extremely weird shape inference bug in foreach
URL: https://github.com/apache/incubator-mxnet/issues/12760#issuecomment-427974399
 
 
   Here's a simpler problem that I believe is the same issue:
   
   ```
   import mxnet as mx
   
   json = """{
   	"nodes":[
   		{
   			"op":"null",
   			"name":"a",
   			"attrs":{},
   			"inputs":[]
   		},
   		{
   			"op":"null",
   			"name":"b",
   			"attrs":{},
   			"inputs":[]
   		},
   		{
   			"op":"_foreach",
   			"name":"foreach",
   			"attrs":{
   				"in_data_locs":"[0,1]",
   				"in_state_locs":"[]",
   				"num_args":"3",
   				"num_out_data":"2",
   				"num_outputs":"2",
   				"remain_locs":"[]"
   			},
   			"inputs":[[0,0,0],[1,0,0]],
   			"subgraphs":[
   				{
   					"nodes":[
   						{
   							"op":"null",
   							"name":"inner_a",
   							"inputs":[]
   						},
   						{
   							"op":"null",
   							"name":"inner_b",
   							"inputs":[]
   						},
   						{
   							"op":"identity",
   							"name":"id_a",
   							"inputs":[[0,0,0]]
   						},
   						{
   							"op":"identity",
   							"name":"id_b",
   							"inputs":[[1,0,0]]
   						}						
   					],
   					"arg_nodes":[0,1],
   					"heads":[[3,0,0],[2,0,0]]
   				}
   			]
   		}
   	],
   	"arg_nodes":[0,1],
   	"heads":[[2,0,0], [2,1,0]],
   	"attrs":{
   		"mxnet_version":[
   			"int",
   			10300
   		]
   	}
   }"""
   
   sym = mx.sym.load_json(json)
   print(sym.infer_shape(a=(3,2), b=(3,5)))
   ```
   
   This prints:
   
   ```
   ([(3, 2), (3, 5)], [(3, 2), (3, 5)], [])
   ```
   
   But it should print:
   
   ```
   ([(3, 2), (3, 5)], [(3, 5), (3, 2)], [])
   ```
   
   Changing the value of `"heads":[[3,0,0],[2,0,0]]` to `"heads":[[2,0,0],[3,0,0]]` does nothing! It should determine the order of outputs of the inner foreach op.

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