The p196_mpi Implementation of the Reverse-And-Add Algorithm for the Palindrome Quest

Łukasz Świerczewski

To quote John Walker, the first person to brute-force the problem [1]: Pick a number. Reverse its digits and add the resulting number to the original number. If the result isn't a palindrome, repeat the process. Do all numbers in base 10 eventually become palindromes through this process? Nobody knows. After the three years of computing that gave its title to Walker paper, many others became interested in the issue. The problem itself is older, and was already mentioned in David Wells book on the subject of interesting numbers [2]. Many people worked on the quest over the decades. The numbers whose existence is questioned were christened Lychrel by Wade VanLandingham, who maintains a comprehensive web site dedicated to them [3]. This research poster describes the implementation of the p196_mpi code, a distributed code dedicated to compute iterations of the palindrome quest as fast as possible. As of the end of 2013, this is the fastest known code to work on the problem. It was the first code to break the 300 million digits mark and subsequently to reach 600 million digits.