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https://github.com/urbanjost/m_factor

Factors of whole numbers
https://github.com/urbanjost/m_factor

factor fortran fortran-package-manager fpm prime-factorisation prime-factorization

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Factors of whole numbers

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README 

        
## ![M_factor](docs/images/factor.gif)

# M_factor



   This is a growing collection of Fortran procedures related to

   factorization of integers and polynomials, and prime factorization.



## Introduction



   Division is basically the reverse operation of multiplication. But

   it gets a little more difficult when your factors can only be whole

   numbers.



   The factors are any of the numbers (or symbols) that form a product

   when multiplied together.



   So, for example an **Integer Factor** is one of two or more integers

   that can be exactly divided into another integer.



   Another equivalent way to define "factor" is that it is quantity

   which is multiplied by another quantity.



   This is in contrast to statistics, where a factor can mean any

   independent variable.



   There are a few basic example programs included as well ...



   + **lcm**      - display least common multiple of a list of whole numbers

   + **factors**  - display prime factors of numbers

   + **gcd**      - display greatest common divisor of a list of whole numbers

   

   All the procedures are gathered into the Fortran module M_factor.f90. So

   far ...



## Name

  M_factor(3fm) - module for least common multiple, greatest

  common divisor, and prime factors



## Synopsis

```text

       use M_factor, only : least_common_multiple, greatest_common_divisor

       use M_factor, only : prime_factors, i_is_prime

```

+ least_common_multiple



    Least common multiple of two integers or vector m(:), matrix m(:,:)

    or cuboid m(:, :, :)



+ greatest_common_divisor



    greatest common divisor of two integers or vector m(:), matrix m(:,:)

    or cuboid m(:, :, :)



+ prime_factors



    decompose a number into its prime factors



+ i_is_prime



    Determine if a number is prime using Sieve of Erasthosthenes



## Description

  This module is a collection of procedures that perform common functions

  found in arithmetic and number theory such as Least Common Multiples,

  Greatest Common Divisors, and Prime Factors of INTEGER variables.

  The INTEGER values are typically limited to values up to the magnitude

  (2**31)-1= 2147483647.



## Examples

  The individual man(1) pages for each procedure contain examples and

  a full description of the procedure parameters.



---

![gmake](docs/images/gnu.gif)

---

## Building the Module using make(1)

     git clone https://github.com/urbanjost/M_factor.git

     cd M_factor/src

     # change Makefile if not using one of the listed compilers

     

     # for gfortran

     make clean

     make F90=gfortran gfortran

     

     # for ifort

     make clean

     make F90=ifort ifort



     # for nvfortran

     make clean

     make F90=nvfortran nvfortran



This will compile the Fortran module and basic example

program that exercise the routine.



---

![-](docs/images/fpm_logo.gif)

---

## Build and Test with FPM



   Alternatively, download the github repository and build it with

   fpm ( as described at [Fortran Package Manager](https://github.com/fortran-lang/fpm) )



   ```bash

        git clone https://github.com/urbanjost/M_factor.git

        cd M_factor

        fpm run "*"

        fpm run --example "*"

        fpm test

   ```



   or just list it as a dependency in your fpm.toml project file.



```toml

        [dependencies]

        M_factor        = { git = "https://github.com/urbanjost/M_factor.git" }

```

---

![docs](docs/images/docs.gif)

---

## Documentation



### User

   - A single page that uses javascript to combine all the HTML

     descriptions of the man-pages is at 

     [BOOK_M_factor](https://urbanjost.github.io/M_factor/BOOK_M_factor.html).



   - a simple index to the man-pages in HTML form for the

   [routines](https://urbanjost.github.io/M_factor/man3.html) 

   and [programs](https://urbanjost.github.io/M_factor/man1.html) 



   - ![man-pages](docs/images/manpages.gif)

     There are man-pages in the repository download in the docs/ directory

     that may be installed on ULS (Unix-Like Systems).



      + [manpages.zip](https://urbanjost.github.io/M_factor/manpages.zip)

      + [manpages.tgz](https://urbanjost.github.io/M_factor/manpages.tgz)



   - [CHANGELOG](docs/CHANGELOG.md) provides a history of significant changes



### Developer

   - [ford(1) output](https://urbanjost.github.io/M_factor/fpm-ford/index.html).



   - [github action status](docs/STATUS.md) 

---

![-](docs/images/ref.gif)

---

## Pedigree



## References



   * [Wikipedia - Factorization](https://en.wikipedia.org/wiki/Factorization)