X10 Language Specification Version 2.5 Vijay Saraswat, Bard Bloom, Igor Peshansky, Olivier Tardieu, and David Grove Please send comments to
[email protected] December 3, 2014 This report provides a description of the programming language X10. X10 is a class- based object-oriented programming language designed for high-performance, high- productivity computing on high-end computers supporting ≈ 105 hardware threads and ≈ 1015 operations per second. X10 is based on state-of-the-art object-oriented programming languages and deviates from them only as necessary to support its design goals. The language is intended to have a simple and clear semantics and be readily accessible to mainstream OO pro- grammers. It is intended to support a wide variety of concurrent programming idioms. The X10 design team consists of David Cunningham, David Grove, Ben Herta, Vijay Saraswat, Avraham Shinnar, Mikio Takeuchi, Olivier Tardieu. Past members include Shivali Agarwal, Bowen Alpern, David Bacon, Raj Barik, Ganesh Bikshandi, Bob Blainey, Bard Bloom, Philippe Charles, Perry Cheng, Christopher Donawa, Julian Dolby, Kemal Ebcioglu,˘ Stephen Fink, Robert Fuhrer, Patrick Gallop, Christian Grothoff, Hiroshi Horii, Kiyokuni Kawachiya, Allan Kielstra, Sreedhar Ko- dali, Sriram Krishnamoorthy, Yan Li, Bruce Lucas, Yuki Makino, Nathaniel Nystrom, Igor Peshansky, Vivek Sarkar, Armando Solar-Lezama, S. Alexander Spoon, Toshio Suganuma, Sayantan Sur, Toyotaro Suzumura, Christoph von Praun, Leena Unnikrish- nan, Pradeep Varma, Krishna Nandivada Venkata, Jan Vitek, Hai Chuan Wang, Tong Wen, Salikh Zakirov, and Yoav Zibin. For extended discussions and support we would like to thank: Gheorghe Almasi, Robert Blackmore, Rob O’Callahan, Calin Cascaval, Norman Cohen, Elmootaz El- nozahy, John Field, Kevin Gildea, Chulho Kim, Orren Krieger, Doug Lea, John Mc- Calpin, Paul McKenney, Josh Milthorpe, Andrew Myers, Filip Pizlo, Ram Rajamony, R.