### Author Topic: Heapsort, VATSort, and ListSort  (Read 2966 times)

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#### Xeda112358

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##### Heapsort, VATSort, and ListSort
« on: July 03, 2018, 10:29:08 pm »

Hey all, I implemented the heapsort algorithm with some features inspired by Sean McLaughlin's implementation. Heapsort operates in O(n*log(n)) time, so it is fast even as array sizes increase. The cool perk to Sean's implementation that I wanted to include in mine is the ability to have a callback function that performs comparisons. This is fantastic if your array contains pointers to, say, an array of strings. The callback function can take the inputs (in my case, HL and DE), perform a string comparison, and return the result to the heapsort routine. Heapsort will then know whether or not to swap the elements.

As an example, I created a VAT sorting routine. It creates an array of pointers to the VAT entries of named variables (like Programs, Appvars, etc.), and then uses a fancy callback function that compares the names of the VAT entries. Returned is an alphabetically sorted array of pointers.

As well, I made a very fast routine to sort TI lists. The callback routine for this takes indices, constructs pointers to the actual list data, compares them, then returns the result. Since the OS routine uses an O(n2) algorithm, my program can perform way faster on larger lists. I ran a few tests on random lists and came up with:

* at 100 elements, the OS routine and my routine were pretty close in speed.
* at 400 elements, my routine sorted it in ~1.3 seconds, versus ~9.5. for the OS routine
* at 999 elements, my routine sorted it in ~3.0 seconds, versus ~55.5. for the OS.

Code: (Heapsort) [Select]
#ifndef scrap
#define scrap 8000h
.echo "Warning, 'scrap' not defined, defining scrap=8000h"
#endif
#ifndef SMC
arraybase= scrap
arraylen = scrap+2
#endif
heapflags= 33
curchild = 0
heapsort:
;   HL points to the array data
;   BC is the size of the array. NOT GREATER THAN 32767
;   IX points to the routine that compares the values
#ifdef fast
call heapify
ld hl,(arraylen)
#else
push bc
call heapify
pop hl
#endif
_:
dec hl
ld (arraylen),hl
#ifndef fast
push hl
#endif
ld de,(arraybase)
inc de
#ifdef fast
ld a,(de)
ldd
inc hl
ld (hl),a
dec hl
ld a,(de)
ldd
inc hl
ld (hl),a
#else
call swap
#endif
ld bc,1
call propogate
#ifdef fast
ld hl,(arraylen)
#else
pop hl
#endif
ld a,h
or l
jr nz,-_
ret
heapify:
;Inputs:
;   HL points to the array data
;   BC is the size of the array. NOT GREATER THAN 32767
;   IX points to the routine that compares the values
ld (arraybase),hl
ld (arraylen),bc
srl b
rr c
_:
push bc
call propogate
pop bc
dec bc
ld a,b
or c
jr nz,-_
ret
propogate:
;BC-1 is the parent index
;2BC is the child1 index
res curchild,(iy+heapflags)
proppost:
sla c
rl b
ld d,b
ld e,c
#ifdef SMC
arraylen=$+1 ld hl,0 #else ld hl,(arraylen) #endif sbc hl,de add hl,de ret c ;no children ;compare the two children #ifdef SMC arraybase=$+1
ld hl,0
#else
ld hl,(arraybase)
#endif
inc hl
ld d,(hl)
dec hl
ld e,(hl)
dec hl
push hl
ld a,(hl)
dec hl
ld l,(hl)
ld h,a
;HL holds the value of child0
;DE holds the value of child1
jr z,+_
call callix
jr nc,+_
ex de,hl
pop de
inc de
inc de
set curchild,(iy+heapflags)
push de
_:
;{stack} points to the child
;HL is the value of the child
;BC points to the parent
;now compare the child and parent
ex de,hl
ld hl,(arraybase)
push hl
dec hl
ld a,(hl)
dec hl
ld l,(hl)
ld h,a
call callix
pop hl
pop de
ret nc
dec hl
call swap
;values swapped, now set parent=child
;BC is the index of child1
bit curchild,(iy+heapflags)
jp z,proppost
inc bc
jp propogate
swap:
;HL points to the top of one word
;DE points to the top of another
;Must preserve BC
#ifdef fast
ld a,(de)
ldd
inc hl
ld (hl),a
dec hl
ld a,(de)
ldd
inc hl
ld (hl),a
inc c
inc bc
#else
call +_
_:
ld a,(de)
ldd
inc hl
ld (hl),a
dec hl
inc bc
#endif
ret
callix:
jp (ix)
Even when optimizing for speed over size, my code is smaller, but I'm fairly sure there are more optimizations to be found!
« Last Edit: March 28, 2020, 03:51:12 pm by Xeda112358 »

#### Eeems

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##### Re: Heapsort, VATSort, and ListSort
« Reply #1 on: July 03, 2018, 11:09:27 pm »
It would be interesting if someone patched a bunch of TI-OS's commands with faster versions like this. That's pretty awesome @Xeda112358. You really need to compile a bunch of your routines into an easy to use library ;P
/e

#### Xeda112358

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##### Re: Heapsort, VATSort, and ListSort
« Reply #2 on: July 03, 2018, 11:24:39 pm »
Haha, I have done something like that in the past. I just put a ton of my math and graphics routines into an App with a jump table to access them. Kind of like Floatlib. Really, I just need to make a Batlib 2 with my new coding techniques and methods and routines and ideas.

#### Eeems

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##### Re: Heapsort, VATSort, and ListSort
« Reply #3 on: July 03, 2018, 11:35:42 pm »
I was thinking more like patching the OS so there would be no extra applications/programs/hooks installed.
/e

#### E37

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##### Re: Heapsort, VATSort, and ListSort
« Reply #4 on: July 09, 2018, 06:16:31 pm »
Ooh that would be cool. Are you allowed to post modified roms? I have a couple of my own that I could add in the extremely low chance anyone does anything about it.
I'm still around... kind of.

#### Eeems

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##### Re: Heapsort, VATSort, and ListSort
« Reply #5 on: July 09, 2018, 07:25:07 pm »
Ooh that would be cool. Are you allowed to post modified roms? I have a couple of my own that I could add in the extremely low chance anyone does anything about it.
You cannot post modified roms as it contain copyrighted content.
/e

#### ibid

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##### Re: Heapsort, VATSort, and ListSort
« Reply #6 on: October 28, 2018, 03:20:43 am »
You don't need to include the rom. You could just post the patches like ThePenguin77 used to do.

#### Xeda112358

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##### Re: Heapsort, VATSort, and ListSort
« Reply #7 on: March 28, 2020, 03:49:50 pm »
Necro Update!
I rewrote the heapsort to be really general-purpose. This significantly reduced the size of ListSort and it made it so that it doesn't require any additional user RAM (but it did make it slightly slower).

I've attached the new heapsort.z80 and listsort.z80

But then I tailored the new heapsort to the task of sorting lists and made it even smaller (200 bytes, saving 157 bytes)! And it is faster, AND this version now uses 15MHz mode if available.

Which reminds me: In the original benchmarks, I was apparently comparing my 6MHz program to TI's 15MHz SortA(, so my program is actually over 50 times faster than TI's on a 999-element list.