Coding tasks for PFN internship
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PFN Internship Coding Tasks

This repository contains coding problems used for the screening process in PFN (Preferred Networks) summer internship.

English and Japanese statements are available. The overview of the problems is as follows.


The problem set in 2018 consists of five themes. Applicants needed to choose one of them according to the theme they have chosen.

  • Machine Learning/Mathematics: You are asked to implement an algorithm of adversarial examples for some neural network model. You need to write a simple report on the performance of the algorithm as well.
  • Back-end: You are asked to create a tool that analyzes log files.
  • Front-end: You are asked to develop a prototype of an annotation tool for speech videos.
  • Processor/Compiler: You are asked to optimize the code of matrix multiplication. Further, you need to design a hardware circuit of matrix multiplication.
  • Chainer: You are asked to implement a training code for some model, using Chainer.


The problem set in 2017 consists of four themes.

  • Machine Learning/Mathematics: Reinforcement learning, Cartpole, Cross Entropy Method.
  • Back-end: Implementation of 'ls' command.
  • Front-end: Creation of search UI.
  • Chip: Hardware circuit design.

Old Problems (2011-2016)

old directory contains older problem sets, which were use also in the summer internship screening of PFI (Preferred Infrastructure, Inc.). Only Japanese statements are available.

  • 2016(PFN, PFI): Unsupervised learning. Auto-encoder and its extension.
  • 2015(PFN, PFI): Supervised learning. Data preprocessing, perceptron, ZCA Whitening, and its extension.
  • 2014(PFI): Template matching.
  • 2013(PFI): Search algorithm on random graphs.
  • 2012(PFI): String processing. Generalized word chain game.
  • 2011(PFI): String processing. Palindrome.

We Are Hiring!

If you got interested in PFN, we are looking forward to receiving your applications in the following internship programs.

We are also hiring full-time employees in Tokyo, Japan and San Mateo, California. Please refer to the job page below.

Reference for PFN internship