u3qb_sort use quicksort

[dozreg-toplud]

Implements +sort jet by building an array of nouns to run quicksort algorithm on. Has much better memory usage for large lists and appears to be faster than the previous implementation: ~:(sort (gulf 1 100.000) gth) used to run out of memory, but not anymore, and ~:(sort (gulf 1 10.000) gth) runs about 2x faster.

[dozreg-toplud]

dont merge it yet, I didnt check for stability

[dozreg-toplud]

+sort reverses the list if comparison gate always returns yes, and preserves the order if it always returns no. is this intentional?

[dozreg-toplud]

rewrote the jet to use merge sort for stability. Notice the reversed comparison here:

vere/pkg/noun/jets/b/sort.c

Lines 38 to 48 in cccde8c

	// reversed comparison to mimick order reversal of pivot
	// and compared element in Hoon
	//
	u3_noun sam = u3nc(u3k(arr_u[j_w]), u3k(arr_u[i_w]));
	u3_noun hoz = u3j_gate_slam(sit_u, sam);
	if ( hoz > 1 ) u3m_bail(c3__exit);
	if ( c3n == hoz )
	tmp_u[k_w++] = arr_u[i_w++];
	else
	tmp_u[k_w++] = arr_u[j_w++];
	}

This is done in order to mimick the behavior of +sort function in Hoon, where the first element of the array is taken as a pivot and then it is passed to the comparator gate as a second argument, the first being the compared list element.

[dozreg-toplud]

tested sort correctness with this dojo expression:

=/  gat1  |=([[@ v1=@] @ v2=@] (lte v1 v2))
=/  gat2  |=([[@ v1=@] @ v2=@] (lth v1 v2))
!.  ^-  ~
=/  one-done  |
=/  gat=$-([[@ @] @ @] ?)  gat1
|-  ^-  ~
=*  gat-loop  $
=*  vals-num  5
=*  len-list  10
=/  perm  (pow vals-num len-list)
|-  ^-  ~
=*  perm-loop  $
?:  =(perm 0)
  ?:  one-done  ~
  gat-loop(gat gat2, one-done &)
=/  l=(list (pair @ @))  ::  idx and value
  =/  c  len-list
  |-  ^-  (list (pair @ @))
  =*  list-loop  $
  ?:  =(c 0)  ~
  :-  [(sub len-list c) (mod perm vals-num)]
  list-loop(c (dec c), perm (div perm vals-num))
::
=/  l1  (sort l gat)
=/  l2  .*([-:sort [l gat] +>:sort] -:sort)
?.  =(l1 l2)
  ~|  ^-  (list [@ @])  l1
  ~|  ;;  (list [@ @])  l2
  !!
~?  =(0 (mod perm 10.000))  perm
perm-loop(perm (dec perm))

Changing comparison in sort jet to

u3_noun sam = u3nc(u3k(arr_u[i_w]), u3k(arr_u[j_w]));
c3_o hoz_o = u3x_loob(u3j_gate_slam(sit_u, sam));
if ( c3y == hoz_o )
//  ...

would make the expression fail