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### About BitBlt for non graphical problems

RL
Rafael Luque
Mon, Dec 21, 2020 9:56 AM

Hi all,

I remember to read in the Blue Book about a Game Of Life solution based on
the BitBlt operation. I wondered if it was only a smart and elegant
demonstration or it may be a useful tool in the case you need
parallelism, even in non-graphical contexts. I've never seen BitBlt used to
solve non-graphical problems, but I don't have experience with BitBlt in my
everyday work, so maybe I'm biased.

I've found a paper by Leo J. Guibas and Jorge Stolfi (
https://www.cs.tufts.edu/~nr/cs257/archive/leo-guibas/language-bitmap.pdf)
about a "calculus of bitmap operations" including an specific language
called MUMBLE, but I suspect it is not a common use case.

Anyway, I've experimented with this option to solve the Advent of Code's
Day 3 challenge. The puzzle consists of counting the number of trees you
will encounter traversing a given map with open squares and trees, starting
at the top-left corner and following a certain slope ((

After implementing the straight-forward and iterative solution, I tried
using Form instances representing the map and the slope and a BitBlt
operation for ANDing both forms in order to leave only bits where you
encounter a tree (see attached image). In this alternative solution I like
how the iteration is replaced by only one "BitBlt>>copyBits" operation.
Additionally, I understand that BitBlt operations are native primitives
that could be hardware optimized.

However, I didn't know how to count the resulting bits without recurring
again to the iteration of the Form's bits. This is my current
implementation:

AoCBitBltForestMap>>countTreesOnPath
| mapForm |
mapForm := self form.
(BitBlt toForm: mapForm)
to: 0 @ 0
rule: Form and.

``````^ mapForm bits count: [ :bit |
(Color colorFromPixelValue: bit depth: 32) green
closeTo: 1
precision: 0.1 ]
``````

You can find all the sources at the following repository:

Any comments about BitBlt use cases or this specific puzzle will be of
interest for me.

Thank you.

Hi all, I remember to read in the Blue Book about a Game Of Life solution based on the BitBlt operation. I wondered if it was only a smart and elegant demonstration or it may be a useful tool in the case you need parallelism, even in non-graphical contexts. I've never seen BitBlt used to solve non-graphical problems, but I don't have experience with BitBlt in my everyday work, so maybe I'm biased. I've found a paper by Leo J. Guibas and Jorge Stolfi ( https://www.cs.tufts.edu/~nr/cs257/archive/leo-guibas/language-bitmap.pdf) about a "calculus of bitmap operations" including an specific language called MUMBLE, but I suspect it is not a common use case. Anyway, I've experimented with this option to solve the Advent of Code's Day 3 challenge. The puzzle consists of counting the number of trees you will encounter traversing a given map with open squares and trees, starting at the top-left corner and following a certain slope (( https://adventofcode.com/2020/day/3). After implementing the straight-forward and iterative solution, I tried using Form instances representing the map and the slope and a BitBlt operation for ANDing both forms in order to leave only bits where you encounter a tree (see attached image). In this alternative solution I like how the iteration is replaced by only one "BitBlt>>copyBits" operation. Additionally, I understand that BitBlt operations are native primitives that could be hardware optimized. However, I didn't know how to count the resulting bits without recurring again to the iteration of the Form's bits. This is my current implementation: AoCBitBltForestMap>>countTreesOnPath | mapForm | mapForm := self form. (BitBlt toForm: mapForm) copyForm: self slopeMaskForm to: 0 @ 0 rule: Form and. ^ mapForm bits count: [ :bit | (Color colorFromPixelValue: bit depth: 32) green closeTo: 1 precision: 0.1 ] You can find all the sources at the following repository: https://github.com/luque/AdventOfCode2020 Any comments about BitBlt use cases or this specific puzzle will be of interest for me. Thank you.
SD
Stéphane Ducasse
Wed, Dec 23, 2020 4:46 PM

I do not have your answer but I see that you are having fun… :)
Continue.

I’m playing with VM implementation for the exact same reason :)

On 21 Dec 2020, at 10:56, Rafael Luque rafael.luque.leiva@gmail.com wrote:

Hi all,

I remember to read in the Blue Book about a Game Of Life solution based on the BitBlt operation. I wondered if it was only a smart and elegant demonstration or it may be a useful tool in the case you need parallelism, even in non-graphical contexts. I've never seen BitBlt used to solve non-graphical problems, but I don't have experience with BitBlt in my everyday work, so maybe I'm biased.

I've found a paper by Leo J. Guibas and Jorge Stolfi (https://www.cs.tufts.edu/~nr/cs257/archive/leo-guibas/language-bitmap.pdf https://www.cs.tufts.edu/~nr/cs257/archive/leo-guibas/language-bitmap.pdf) about a "calculus of bitmap operations" including an specific language called MUMBLE, but I suspect it is not a common use case.

Anyway, I've experimented with this option to solve the Advent of Code's Day 3 challenge. The puzzle consists of counting the number of trees you will encounter traversing a given map with open squares and trees, starting at the top-left corner and following a certain slope ((https://adventofcode.com/2020/day/3 https://adventofcode.com/2020/day/3).

After implementing the straight-forward and iterative solution, I tried using Form instances representing the map and the slope and a BitBlt operation for ANDing both forms in order to leave only bits where you encounter a tree (see attached image). In this alternative solution I like how the iteration is replaced by only one "BitBlt>>copyBits" operation. Additionally, I understand that BitBlt operations are native primitives that could be hardware optimized.

However, I didn't know how to count the resulting bits without recurring again to the iteration of the Form's bits. This is my current implementation:

AoCBitBltForestMap>>countTreesOnPath
| mapForm |
mapForm := self form.
(BitBlt toForm: mapForm)
to: 0 @ 0
rule: Form and.

`````` ^ mapForm bits count: [ :bit |
(Color colorFromPixelValue: bit depth: 32) green
closeTo: 1
precision: 0.1 ]
``````

You can find all the sources at the following repository: https://github.com/luque/AdventOfCode2020 https://github.com/luque/AdventOfCode2020

Any comments about BitBlt use cases or this specific puzzle will be of interest for me.

Thank you.

<Captura de pantalla 2020-12-21 a las 10.50.26.png>

Stéphane Ducasse
http://stephane.ducasse.free.fr / http://www.pharo.org
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