```// ************************************************************************** //
//                                                                            //
//    eses                   eses                                             //
//   eses                     eses                                            //
//  eses    eseses  esesese    eses   Embedded Systems Group                  //
//  ese    ese  ese ese         ese                                           //
//  ese    eseseses eseseses    ese   Department of Computer Science          //
//  eses   eses          ese   eses                                           //
//   eses   eseses  eseseses  eses    University of Kaiserslautern            //
//    eses                   eses                                             //
//                                                                            //
// ************************************************************************** //
// ShellSort [Shel59,Cyph89,PlPS92,Sedg96,JiLV00,Ciur01] is usually presented //
// as a variant of InsertionSort (see comments in file ShellSort). However, it//
// can also be used with BubbleSort to perform a gap-sorting of the sequence, //
// which is remarked in many references including [Sedg96]. Using BubbleSort  //
// allows to implement ShellSort as a sorting network as shown below. The     //
// remarkable fact is that using the gap sequence 1,2,3,4,6,8,9,12,16,...,    //
// 2^p3^q one obtains a sorting network of depth O(N*log^2(N)) which is the   //
// same depth as the sorting networks obtained by MergeSortBitonic and        //
// MergeSortOddEven. The implementation of ShellSort is however much simpler, //
// however, it requires more comparators than MergeSortBitonic and            //
// MergeSortOddEven.                                                          //
// ************************************************************************** //

macro aSize = 16;
macro iSize = 64;
macro hSize = 8;

macro step(i) =
(i==0?12
:(i==1?9
:(i==2?8
:(i==3?6
:(i==4?4
:(i==5?3
:(i==6?2:1)))))));

module ShellSortNet1([aSize]nat{iSize} ?a,b, event !ready) {

for(i=0..aSize-1)
b[i] = a[i];

// perform one round of BubbleSort using gaps steps(0)..steps(hSize-1);
// note that steps(i) of the swaps in round s=stop
for(s=0..hSize-1) {
for(i=0..aSize-step(s)-1) {
if(b[i]>b[i+step(s)]) {
next(b[i+step(s)]) = b[i];
next(b[i]) = b[i+step(s)];
}
if(i%step(i)==0) pause;
}
}
}
drivenby Test01 {
for(i=0..aSize-1) a[i] = i;
for(i=0..aSize-1) assert(b[i] == i);
}
drivenby Test02 {
for(i=0..aSize-1) a[i] = aSize-1-i;