An update on the development status of post-K

Fujitsu Limited,RIKEN

Tokyo, June 21, 2018Fujitsu Limited and RIKEN today announced that the joint development of post-K, a supercomputer that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) has set forth as a successor to the K computer, is moving forward, with the goal of beginning full operations around 2021. Fujitsu has now completed the prototype CPU chip that will serve as the core of post-K, commencing functionality field trials.

Fujitsu Completes Post-K Supercomputer CPU PrototypeWith post-K, Fujitsu and RIKEN aim to create the world’s highest-performing supercomputer, capable of tackling a broad range of applications to solve problems not only in the area of science and technology, but to play a role in a wide variety of issues in society. To realize this goal, Fujitsu has adopted the widely used Arm® instruction set architecture (ISA) in the CPU, while implementing expanded instructions newly formulated for supercomputers. In addition to further enhancing the high memory bandwidth and double-precision arithmetic performance implemented in the K computer, Fujitsu has also added support for half-precision arithmetic, which remains critical to fields like AI. Now, by verifying the initial operation of prototype CPU chips meeting these design standards, Fujitsu and RIKEN have smoothly cleared an important milestone in system development.

Moving forward, Fujitsu and RIKEN will continue development with an eye toward completing post-K and commencing full operations.

The post-K prototype will be exhibited at ISC 2018, a significant international conference and exhibition for high performance computing, which will be held in Germany from June 24-28.


Fujitsu and RIKEN began joint development of the K computer in 2006, which was completed and commenced full operations in 2012. The K computer continues to deliver world-leading performance on major indicators of practical supercomputer performance, operating as an indispensable R&D platform for cutting-edge research.

As a successor to the K computer, post-K is also expected to simultaneously serve as a cutting-edge R&D platform for resolving a variety of scientific and society-wide issues, as well as an important platform supporting the attainment of “Society 5.0”(1), a new, human-centric society envisioned by the Japanese government.

Fujitsu began basic design work with RIKEN in October 2014, undertaking co-design work with application developers in a variety of fields while pushing forward with prototyping and detailed specifications.

Development Status of Post-K

Fujitsu and RIKEN have adopted the widely used Arm architecture, envisioning utilization by a broader user base. In addition to this, Fujitsu worked with Arm to contribute to the Scalable Vector Extension (SVE) in the Armv8-A architecture, which significantly extends the vector processing capabilities for HPC systems, and adopted the results. Post-K is also expected to see expanded use in the AI field, delivering support for half-precision arithmetic, important in workloads such as deep learning, as well as the double-precision arithmetic essential for use cases including computer simulations.

Now that Fujitsu has completed CPU chip prototypes and verified their initial operation, it will commence with functionality trials. Going forward, it will continue further development with RIKEN.

Overview of the Post-K System

Fujitsu and RIKEN continue to improve on the technology first introduced in the K computer, which has a proven record for availability and real-world performance, developing post-K as a supercomputer that offers top-class, real-world performance for a wide variety of application software.

The CPUs, which form the core of the system, utilize the Arm8-A SVE architecture, building on the microarchitecture hardware design experience Fujitsu has cultivated through previous supercomputer development projects, including the K computer. With the memory bandwidth delivered by high performance stacked memory computational performance, the post-K system is optimized to achieve high-level, real-world application performance.

Moreover, by utilizing cutting-edge semiconductor technology and by incorporating an energy-saving design and power control functionality, the CPUs deliver excellent energy savings for its performance.

Fujitsu will continue to provide compatibility with the K computer in the system software for post-K, including in the program development environment. By maintaining continuity in language specifications and microarchitecture, the program assets built up for the K computer can be reliably migrated by recompiling them, which can preserve performance standards. In addition, system software developed by RIKEN, including McKernel, XcalableMP, and FDPS (“Framework for Developing Particle Simulator”), can also be used. Fujitsu anticipates that these assets will prove useful in further improving the real-world performance and convenience of the system.

The Arm architecture used in post-K has been accepted by a wide range of developers and users. Joining this community will make it possible for post-K to utilize a wide range of software assets, including open source software. By simultaneously feeding back the results and technology attained through the development of post-K into the community, Fujitsu also hopes it will contribute to the creation of an ecosystem around the Arm architecture.

Fujitsu and RIKEN are continuing development with the goal of generating cutting-edge research results through the use of post-K. This includes resolving scientific and society-wide issues in areas such as health and longevity, disaster prevention and mitigation, energy, and manufacturing, to effectively contribute to enhanced industrial competitiveness.

System Characteristics

Post-K will be a system featuring world-leading capabilities in (1) energy consumption performance, (2) computational capability, (3) ease of use and convenience for users, and (4) generating groundbreaking results, surpassing other systems around the world in overall strength. Moreover, Fujitsu and RIKEN are collaboratively developing both the system and its applications, aiming for the world’s highest level of versatility, up to one hundred times the application execution performance of the K computer, and a power consumption of 30-40 MW (compared with 12.7 MW for the K computer).

Major Specifications for Post-K

Major Specifications for Post-K
Category Details
CPU Instruction set architecture Armv8-A SVE (512bit)
Number of cores Computational nodes: 48 cores + 2 assistant cores
I/O and computational nodes: 48 cores + 4 assistant cores
Built-in interconnect Tofu (6D Mesh/Torus)
System structure Nodes 1 CPU/node
Racks 384 nodes/rack
Software OS Linux (RHEL-based) + McKernel (Lightweight Kernel)
System software Successor to the Fujitsu Software Technical Computing Suite
Global file system FEFS (Lustre-based)
Language Successor to the Fujitsu Software Technical Computing Language (Fortran/C/C++, OpenMP, MPI), XcalableMP
Library framework FDPS (Framework for Developing Particle Simulator)

Research Topics Using Post-K

Post-K is expected to generate world-leading results, particularly in scientific and society-wide issues that should be the focus of efforts (priority issues and emerging issues), as shown below. For this reason, Fujitsu and RIKEN are undertaking co-design work with application developers for these issues in post-K system development, with the goal of delivering outstanding performance in a wide range of fields of use.

Priority Issues

  1. The creation of a revolutionary drug discovery platform through functional control of biomolecular systems
  2. Integrated computational life sciences supporting individualized and preventative medicine
  3. The creation of integrative prediction systems for compound disasters caused by earthquakes and tsunamis
  4. Improved predictions of the climate and global environment using observational big data
  5. The development of new foundational technologies for the efficient creation, conversion, storage and use of energy
  6. The development of practical implementations for revolutionary green energy systems
  7. The creation of high performance materials and devices offering new functionality supporting next-generation manufacturing
  8. The development of revolutionary design and manufacturing processes leading near future manufacturing
  9. The elucidation of evolution and the fundamental laws of the universe

Emerging Issues

  1. Taking on the challenges of the outermost frontiers of foundational science
  2. The building of models of the interactions of multiple socioeconomic phenomena, and research into their applications
  3. Clarifying the processes surrounding the formation of extra-solar planets (new earths), and of environmental change on planets in this solar system
  4. The elucidation of the mechanisms of the neural circuitry that produces thought, and its application to artificial intelligence

Comments from Fujitsu, RIKEN, and Arm

Comment from SEVP Akira Kabemoto, Head of the Service Platform Business at Fujitsu Limited

We are extremely pleased to announce genuine progress in the development of the post-K computer. Fujitsu has been developing and delivering the world’s top level supercomputers for over 40 years. The use of supercomputers has expanded beyond contributing to the development of science and technology through simulation to encompass areas like AI, emphasizing their importance as part of the infrastructure of society. With post-K, I believe we’ve combined all the various, cutting-edge technologies we have developed until now to create the world’s leading supercomputer. We hope this will ultimately contribute to the achievement of an abundant, human-centric future filled with dreams.

Comment from Satoshi Matsuoka, Director, RIKEN Center for Computational Science (R-CCS)

Because an architecture suited for high performance computing was co-designed by Fujitsu and R-CCS, the post-K processors are expected to (1) deliver performance far surpassing that of existing general-purpose server processers for many supercomputer applications, and (2) considerably raising the system’s usability by using a broad software ecosystem through the adoption of the Arm instruction set, while at the same time (3) delivering top-class performance not just in simulations, but also in a wide range of fields related to Society 5.0, including artificial intelligence and machine learning, security and blockchain technology, big data, and IoT. In this way, I am certain that post-K will not only contribute world-leading performance to meet the concerns of the people of Japan, it will also be a sign of the revitalization of Japan’s semiconductor technology. Having now verified the operation of the prototype CPU as planned, we have cleared a major step in the path to full operation of post-K around 2021, as well as toward subsequent developments. Going forward, R-CCS intends to even more vigorously pursue research and development, in collaboration with other related parties, in order to begin operations using post-K, the world’s top supercomputer, as soon as possible. Please look forward to it.

Comment from Drew Henry, senior vice president and general manager, Infrastructure Line of Business, Arm

Arm has been deeply engaged with both Fujitsu and RIKEN, working to build an HPC ecosystem for the Armv8-A SVE architecture, opening a new chapter for Arm technology to scale the levels of vector processing. Our collaboration with Fujitsu and RIKEN represents our ongoing commitment to maximizing the success of the post-K design and marks a significant step toward deploying Arm-based technologies for HPC and potentially for a broader set of emerging applications.