question: private static void sort1 ( double [ ] x , int off , int len ) { if ( len < 7 ) { for ( int i = off ; i < len + off ; i ++ ) for ( int j = i ; j > off && x [ j - 1 ] > x [ j ] ; j -- ) swap ( x , j , j - 1 ) ; return ; } int m = off + ( len > > 1 ) ; if ( len > 7 ) { int l = off ; int n = off + len - 1 ; if ( len > 40 ) { int s = len / 8 ; l = med3 ( x , l , l + s , l + 2 * s ) ; m = med3 ( x , m - s , m , m + s ) ; n = med3 ( x , n - 2 * s , n - s , n ) ; } m = med3 ( x , l , m , n ) ; } double v = x [ m ] ; int a = off , b = a , c = off + len - 1 , d = c ; while ( true ) { while ( b <= c && x [ b ] <= v ) { if ( x [ b ] == v ) swap ( x , a ++ , b ) ; b ++ ; } while ( c >= b && x [ c ] >= v ) { if ( x [ c ] == v ) swap ( x , c , d -- ) ; c -- ; } if ( b > c ) break ; swap ( x , b ++ , c -- ) ; } int s , n = off + len ; s = Math . min ( a - off , b - a ) ; vecswap ( x , off , b - s , s ) ; s = Math . min ( d - c , n - d - 1 ) ; vecswap ( x , b , n - s , s ) ; if ( ( s = b - a ) > 1 ) sort1 ( x , off , s ) ; if ( ( s = d - c ) > 1 ) sort1 ( x , n - s , s ) ; }
target:  Sorts the specified sub-array of doubles into ascending order.