Author:

• Name: Fabrice Bellard
  Location: FR - French Republic (France)

To build:

    make

To use:

    ./bellard

Judges’ remarks:

This code is a nice compact example of a Modular Fast Fourier Transform. While its output is very specific, the internal FFT has a wide variety of uses.

Can you modify this code to produce primes such as 23523*2^70000-1, 48594^65536+1 or 6917!-1?

NOTE: as bigger primes are found as time goes by this program no longer prints the biggest prime once noted by the author below.

Author’s comments:

This program prints the biggest known prime number (2^6972593-1) in base 10. It requires a few minutes. It uses a Modular Fast Fourier Transform to compute this number in a reasonable amount of time (the usual method would take ages !).

The program uses >= 64 bit long long type. It should run on any system with a gcc compiler.

Primary files

• bellard.c - entry source code
• Makefile - entry Makefile
• bellard.orig.c - original source code

Secondary files

• 2000_bellard.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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