An arithmetic processing system includes an external memory and an arithmetic-logic unit. The arithmetic-logic unit performs at least operations of 1) acquiring a first partition map from each input feature map stored in the external memory, the first partition map being one of partition maps included in the input feature map; executing a convolution operation on the first partition maps acquired from the external memory; storing, in the external memory, first partition maps that have undergone the convolution operation, and 2) acquiring a second partition map from each input feature map stored in the external memory, the second partition map being one of the partition maps; executing a convolution operation on the second partition maps acquired from the external memory; and storing, in the external memory, second partition maps that have undergone the convolution operation.