Programmer tries to explain binary search to the police

Yeah, pigs don't like to be corrected. Or made to look like they don't know what they're doing.

This argument did not go well

You can't convince people to do their job with logic when they just don't want to do their job. After minorities, the thing cops hate most is doing their job.

I thought this had to be hyperbole, so I did the math myself. I'm assuming human history is 200,000 years as google says, and we want to narrow this down to the second the bike disappeared. also that the bike instantly vanished so there's no partially existing bike.

each operation divides the time left in half, so to get from 200k years (6.311×10^12 seconds) to 1 would take ~42.58 divisions, call it 43. even if we take a minute on average to seek and decide whether the bike is there or not it would still be less than an hour of manual sorting

hell, at 60fps it would only take another 6 divisions to narrow it down to a single frame, still under an hour

edit: to use the entire hour we'd need a couple more universes worth of video time to sort through, 36.5 billion years worth to be exact. or a measly 609 million years if we need to find that single frame at 60fps

This didn't go down well.

IT consulting pro-tip: Customers would rather pay for your time and expertise, than be made to feel stupid that they didn't think of something so simple themselves.

This method will take forever to find the exact moment, said Officer Zeno.

I'm a little surprised the police didn't already know about that method. Seems like they'd encounter enough CCTV footage that'd it'd be standard training.

I once again overestimate the training levels of the police.

This post just shows that the police rarely if ever review any video as this method would've been learned as a result of repeatedly reviewing video.

Part of my job is to review security footage for reported incidents.

If there is a long-lasting visual cue that the event has or has not happened yet (e.g. a window is either broken or not), then a binary search is very useful.

If the event lasts only a moment and leaves no visual cue (e.g. an assault), then binary search is practically useless.

Police try to understand anything challenge (100% impossible) (gone sexual) (gone violent)

That's how I look for broken mods too. Move half of them into a temp folder, launch the game. If it works, put half of the sorted out ones back. if it doesn't work, remove another half and try again.

"Exactly my point. We will not be investing an hour looking at the footage to pinpoint the time of theft, now get out!"

just tell them there is a black man at the moment of theft, they will get on it lickety split!

I'm sure it didn't go well. If it was somehow framed in a sycophantic way where the police were led to believe it was their idea, I'm sure it would have gone better. Wait that might not be too difficult to do.

Sounds about right. Cops have low iqs

It would have taken 5 minutes at most

Their method actually does make sense, you just have to remember they aren't cops to solve (boring) crimes like petty theft. Why get it done as efficiently as possible when you can milk it for hours of overtime? 12 hours of footage means 6+ hours of overtime even watching it at x2 speed, and it's the kind of thing you can basically have going on in the background. Cops being willfully ignorant for their own benefit makes sense to me

“This argument didn’t go down well.”

🤣🤣🤣 LMAO

What an awesome punchline, should have been on its own line for more impact.

When troubleshooting physical systems, it's called half-splitting

https://www.ecmweb.com/maintenance-repair-operations/article/20889049/the-beauty-of-halfsplitting

God damn, whoever came up with that is clever. I would have never come up with that on my own.

Jesus fucking Christ, I know police are dumb, in fact if your IQ is too high you can actually be legally barred from employment as a police officer in the United States of america. Look it up. But fuck incompetence of these Jokers continue to tickle my asshole in a negative way

The final project in my instrumentation class was to tune a PID controller for a hot/cold mixing valve. I (CS/ENG) was paired up with an engineering student and a lot of it was throwing parameters in, seeing if weird shit happened, and then turning down or up based on the result. I had a programming final and something else I was supposed to be studying for, so I just started doing a binary search with the knobs. We got the thing tuned relatively fast and my partner acted like I was a wizard.

Oh yea this is how I managed to convince our building management company to identify bicycle thieves in our communal garage.

This is how I look for the best bits in porn

A police officer being unable to think in such a fashion is exactly why no one could solve the see-saw riddle on Brooklyn 99.

acab

that dawn of humanity is only going to work if the rewind/fast forward is instantaneous.

They're paid by the hour.

I'm realizing now that this would have been super useful when I worked in Loss Prevention way back when. Wish I had known...

I mean, in the era of VHS this won't work because ultimately you're fast forwarding and rewinding. So you're gonna watch it anyway. but in the digital era I thought this would be what any Police officer did?

Like... they're not even gonna spend 10 minutes on a theft?

In Artillery you call it bracketing/straddling.

For anybody else looking for the source of this quote: https://archive.md/RyZI0

What are we supposed to believe this is some sort of magical VCR?

I used to do this when having problems while rendering video in my past life.

image transcription:

Afterwards I found a chatroom thread among Cambridge computer scientists, one of whom had also been told that unless he could pin down the moment of theft no one would look at the footage. He said he had tried to explain sorting algorithms to police - he was a computer scientist, after all. You don't watch the whole thing, he said. You use a binary search. You fast forward to halfway, see if the bike is there and, if it is, zoom to three quarters of the way through. But if it wasn't there at the halfway mark, you rewind to a quarter of the way through. It's very quick. In fact, he had pointed out, if the CCTV footage stretched back to the dawn of humanity it would probably have only taken an hour to find the moment of theft. This argument didn't go down well.

This sparked something magical OP.

I was in exactly this situation. My bike was stolen, there was CCTV, they said it would take hours to go through the time during which it was stolen.

Source article for the curious, and an unpaywalled copy on archive.is

Pfft, didn't even try to enhance the footage. They're obviously not cut out for forensics work.

This post is horrifying, not funny.

That's a search algorithm, not sorting

This student should never go to xitter. Or will be canceled instantly.

everyone is a little bit gay!

I do not get why it would work in that case. I assume the scenario is someone with a bike coming, doing theft, then leaving with the same bike.

Therefore there will be a period without bike, then a period with bike, then a period without bike again.

Let's assume there is no bike on the particular moment viewed. How do you know whether it occured before or after the theft? If you make the wrong decision, you get stuck on an endless binary search.. Unless you take note at each timestamp where you made the decision, draw a tree of timestamps, and go back the tree if your search is fruitless but that's much more complicated than what this post says.

I get the sentiment, but you want them to waste public resources doing it on all these different clunky uis and software? Sometimes these take minutes to load new information to parse.

Maybe waste your time pinpointing it instead of expecting public resources to do what you could do for them?