README.md

multiplicative-persistence

Search for integers with high multiplicative persistence values.

Installation

This project uses the standard rustup and cargo toolchain. Originally tested against rustc 1.33.0.

Usage

Build binaries with cargo build --release --bins, they will be output in target/release:

• mpersist
  • for: get the multiplicative persistence of any positive integer
  • list: get the multiplicative persistence of values in a range
  • search: look for the smallest integer with the largest multiplicative persistence value
• mp-visualize

Data generation

./mpersist for 12     # 1
./mpersist -- for 77  # 4

./mpersist search
3 39
4 77
# etc.

# Search for mp values
# - starting with integers 233 digits in length
# - search for 10 rounds (i.e. search up to 243 digits in length)
# - use 4 threads
./mpersist search -f 233 -n 10 -t 4
# this might take some time!

Visualization

For visualization examples, see the example directory. The mp-visualize binary reads the output of mpersist list from stdin, and lays it out in a Sacks spiral.

./mpersist list 0 3500 | ./mp-visualize default.png
./mpersist list 0 100000 | ./mp-visualize -d 0.5 -a 0.25 -r 4 -f 2.0 -w 900 shockwave.png
./mpersist list 0 25000 | ./mp-visualize -d 0.25 -a 0.25 -r 3.5 stars.png

A visualisation of the first 3500 integers and their mp values