This program allows for quickly searching for sequences of digits in pi. This is achieved by generating a custom index on the digits.
You'll need to provide a source of digits in the form of ASCII/UTF-8, such as the one listed here (pi-billion.txt):
$ ./pipattern 12345678
186557266: 1234567805029135
295024271: 1234567855807249
328286393: 1234567869790828
501918952: 1234567807946746
516776780: 1234567832726891
523551502: 1234567892248644
691782818: 1234567807127372
773349079: 1234567895949720
956753746: 1234567870553515
The initial run will build the index (4GB for 1 billion digits) as needed before performing the search. Subsequent runs will be very fast. For the index to be completed in any reasonable about of time, you'll need at least 6GB of RAM for indexing 1 billion digits. Otherwise it will thrash your computer and take a very long time.
This utility was inspired by the Pi-Search Page.