Unnecessary WordPress overhead: the wp hook incorrect use

overhead.php

<?php
  // Never ever use the wp hook to run unnecessary routines
  // Global overhead ahead!

  function my_factorial( $n ) {
      if( function_exists( 'gmp_fact' ) ) {
          return gmp_fact( $n );
      } else {
        if ( $n < 2 ) { 
            return 1; 
        } else { 
            return ( $n * my_factorial( $n - 1 ) ); 
        } 
      }
  }

  function my_wp_func() {
      $numbers = range( 1, 1000000 );
      $factorials = array_map( 'my_factorial', $numbers );
  }

  add_action( 'wp', 'my_wp_func' );
?>