## David H. Bailey## "Computo ergo sum."## http://www.davidhbailey.com |

- Senior Scientist (retired), Computational Research Department, Lawrence Berkeley National Laboratory.
- Research Associate, Department of Computer Science, University of California, Davis.

*Computational and experimental mathematics*. Bailey is also a leading figure in the field of computational and experimental mathematics, applying high performance computing to problems in research mathematics. He is author or co-author of six books and over 100 papers in this field, many of them in conjunction with his long-time collaborator Jonathan M. Borwein of the University of Newcastle, Australia (deceased August 2, 2016). Bailey is also a co-author of two widely used high-precision computation software packages. His best-known paper in this area, "On the rapid computation of various polylogarithmic constants," co-authored with Peter Borwein (Jonathan Borwein's brother) and Simon Plouffe, describes a new formula for pi that permits one to directly calculate binary digits of pi beginning at an arbitrary starting position (this formula was discovered using Bailey's computer implementation of the PSLQ algorithm). In two more recent papers, Bailey and the late Richard Crandall demonstrated a connection between these formulas and a fundamental question about digit randomness. Bailey has received the Chauvenet Prize and the Merten Hesse Prize from the Mathematical Association of America, and the Levi L. Conant Prize from the American Mathematical Society.

*Financial mathematics*. Bailey, together with his colleagues Jonathan Borwein (deceased), Marcos Lopez de Prado (of Guggenheim Partners) and Jim Qiji Zhu (of Western Michigian University), have written a series of papers on mathematical finance. Their best-known paper in this area, Pseudo-mathematics and financial charlatanism: The effects of backtest overfitting on out-of-sample performance has attracted considerable interest in the field (see Press reports for details).

*Other activities*. Bailey operates the Math Scholar blog, devoted to mathematics, computing and modern science, and (in conjunction with Marcos Lopez de Prado and Jim Qiji Zhu) the Financial Math blog, devoted to financial mathematics and abuses of mathematics in the field. He has also written articles for the Huffington Post and the Conversation -- see publication list below.

See Books directory for a list of published books, and Papers directory for a full list of over 290 papers, including, in most cases, web links to preprint copies.

**Math Scholar blog**. Bailey operates a blog devoted to mathematics, computing and modern science:

**Financial Mathematics blog**. Bailey, together with his colleagues Marcos Lopez de Prado and Qiji Jim Zhu, operate a blog devoted to financial mathematics, focusing on overfitting and other abuses of mathematics in the field:

**Disclaimer and copyright**. This site is owned and operated by David H. Bailey. Material on this site is provided for research purposes only, and does not necessarily reflect the views or policies of the Lawrence Berkeley National Lab, the University of California, Davis or any other organization. Except where explicitly stated otherwise, all material on this site is copyrighted by David H. Bailey (c) 2017.

- Photo of Bailey with pi banner (as shown at the top of this page): DHB pi banner
- High-resolution version of full pi banner (20 Mbyte): DHB pi banner (20 Mbyte)
- Photo of Bailey with an LBNL shuttle bus displaying pi poster: Shuttle bus
- Photo of an auto previously owned by Bailey, together with several researchers involved in calculations of pi (Yasumasa Kanada, Eugene Salamin and William Gosper): Auto photo
- Personal photo of Bailey (black/white, vertical format, 1 Mbyte): Bailey photo (1 Mbyte)
- Personal photo of Bailey (color, vertical format, 2.6 Mbyte): Bailey photo (2.6 Mbyte)
- Personal photo of Bailey (color, horizontal format, 2.5 Mbyte): Bailey photo (2.5 Mbyte)
- Bailey near summit of Half Dome: Bailey at Half Dome

This formula, now known as the "BBP formula for pi", permits one to compute binary or hexadecimal digit of pi beginning at an arbitrary starting position n, without needing to compute any of the first n-1 digits, by means of a simple scheme that requires very little memory. It was originally discovered by Simon Plouffe using a computer program written by Bailey that implements a simplified version of Helaman Ferguson's "PSLQ" algorithm. More recently, Richard Crandall and Bailey have shown that there is a connection between the new pi formula and the centuries-old question of normality (ie, statistical randomness of digits in a certain sense) of pi and various other math constants.

Some additional information on pi:

- Bailey's pi website: http://www.davidhbailey.com/pi
*Science News*article (April 24, 2004): PDF (5 Mbyte)*Scientific American*article (May 2003): PDF- See if your name is coded in the first four billion binary digits of pi: http://pi.nersc.gov
- Fax to Bailey from "The Simpsons" TV show:
PDF.

Note: The 40,000th digit of pi was provided to the show by Bailey, and this was aired in the show on 6 May 1993 -- search for "Marge in Chains" at Simpson math website.