1. A method of image tagging on a mobile device comprising: accessing, by one or more processors of the mobile device, image data for a first image; initiating, by the mobile device, processing of the image data using a deep convolutional neural network (DCNN) executed by the one or more processors, the DCNN comprising at least a first subgraph and a second subgraph, the first subgraph comprising at least a first layer and a second layer; processing, by the mobile device, the image data using at least the first layer of the first subgraph to generate first intermediate output data; processing, by the mobile device, the first intermediate output data using at least the second layer of the first subgraph to generate first subgraph output data; in response to a determination that each layer reliant on the first intermediate output data have completed processing, deleting the first intermediate output data from the mobile device; processing, by the mobile device, the first subgraph output data using a first layer of the second subgraph to generate second intermediate data; processing, by the mobile device, the second intermediate data using a second layer of the second subgraph to generate second subgraph output data; and in response to a second determination that each layer reliant on the second intermediate data has completed processing, deleting the second intermediate data from the mobile device.