In the morning, by the small river.
Lin Zhaoxi threw the scraps of paper into the river, not far away, Chen Zhu waved at her.
Lin Zhaoxi was startled.
"Why did you just throw garbage into the river?" Chen Zhu walked towards her with a bun in his mouth.
"Don't tell the teacher." Lin Zhaoxi made nonsense, took the bag from Chen Zhu, took out the small bun from it, and took a bite.
Chen Zhu looked around: "Why hasn't Pei Zhi come yet?"
"He's busy."
Chen Zhu was stunned: "What happened to him?"
"Why do you think something happened to him?" Lin Zhaoxi walked towards the bridge.
"When was Pei Zhi late?"
Lin Zhaoxi thought, Brother Pei seems to have always been so meticulous in his life: "Something happened, but there is no way to solve it."
If it was Comrade Lu, he would probably drag her and ask her what happened, why she didn't help Pei Zhi, and so on.
But Chen Zhu was very straightforward, just said: "Oh, call me if necessary."
Lin Zhaoxi patted Chen Zhu's shoulder: "Of course I need you."
—
Chen Zhu's house, a small garage.
Lin Zhaoxi turned on the switch, and the light shone on the chair where she and Pei Zhichang were sitting.
The water cup she used on the table was clean and bright, and Pei Zhi washed it for her when she left last time.
Chen Zhu had already sat down and turned on the computer, the machine was buzzing, Lin Zhaoxi calmed down, and then turned on the monitor.
About two weeks ago, she completed the forecasting program, but to test whether the program works, she still needs to predict specific events.
But what to choose, becomes tricky again.
Lin Zhaoxi originally wanted to ask Chen Zhu's father to find a hit-and-run case, and the program would calculate the best arresting location and arrange for the police to handle it.
Although it is easy to say, Lin Zhaoxi also knows that this is not a resource that a high school student can mobilize for extracurricular activities.
Still, she tried to make a request.
Chen Zhu's father rejected her after hearing a few words. Adults feel that students have to focus on their studies.
"You only need to tell us the time and place of the escape, and some basic monitoring data, and you don't need to disclose anything else."
"Day and night, uncle knows that you have ideas, but here is China, which is not as open as foreign education, and many things are not practical."
It probably means that the leaders will not allow their high school students to participate in the arrest of hit and run, even in the name of extracurricular practice.
Lin Zhaoxi really wanted to say, before I did this, I also felt that many things seemed like fantasy, but after I did it, I found that it was actually not as incredible as I imagined.
But before she had time to explain, there was a sudden commotion in the new village.
Several aunts in the garden were shouting, some shouted "Oh, hurry up", and some shouted "Call 110".
It happened that a neighbor knew that Chen's father was a traffic policeman, so he ran to their garage and shouted, "Oh, old Chen, do you think the law and order is a problem now, and the car is lost again!"
Lin Zhaoxi followed and listened for a while, only to find out that there have been frequent thefts of battery cars in the community recently.
The new village is too old, the security is ineffective, and there is no fence, so the theft gang loves the Aimin community.
At that time Pei Zhi was by her side, she and Pei Zhi glanced at each other and had a new plan.
She no longer obsessed with hit and run, but began to investigate the theft of battery cars in Aimin Xincun.
Statistics of the time and frequency of theft, nearby traffic data, the speed of the battery car, the places commonly used by thieves to sell stolen goods, etc.
The purpose is to catch the thief.
To do this, they changed some prediction parameters and re-tuned the program.
According to the prediction results fitted by the time and frequency of the incident, it points to the early Sunday morning camp. During this period of time, commuters generally take a break, and there are few people in the new village, and there are high incidences of battery car theft.
Originally, they were almost ready, so they just waited at the spot, but Pei Zhi was not here, so many arrangements had to be made again.
"What should we do?" Chen Zhu asked.
"Then you can only squat in front of the computer to see the results, and I'll go out."
"Isn't it necessary to adapt to the situation, change the parameters, etc. I can't do these things, so I'll go." Chen Zhu paused, "And how can you catch a thief as a girl?"
"Uh... I sometimes forget that I'm a girl."
Lin Zhaoxi said honestly.
—
It was 6:01am on a Sunday morning and the wait was long.
Yesterday, she didn't sleep for more than 4 hours, Lin Zhaoxi sat in front of the computer for a while, and became sleepy.
She just drank a cup of instant coffee and it didn't help at all. As a last resort, she could only ask Chen Zhu if he had tea.
"There is a canteen, you go, and bring me a pack of chewing gum by the way." Chen Zhu said.
Lin Zhaoxi walked out of the garage, the sky was still gray. She stretched her waist, saw Chen Zhu's father coming down the stairs, and waved his hand to say hello to Old Chen.
Chen Jianguo was yawning. Seeing this, he hurriedly put away his tired face: "Chaoxi, why are you here so early?"
"We are squatting with the gang who stole the battery car." Lin Zhaoxi said directly.
Old Chen was stunned for a moment, looking at the girl's upright face, he felt helpless: "You guys..."
He and Lin Zhaoxi went to the canteen together.
The girl asked for a pack of "Mankouxiang" tea, five yuan. Chen Jianguo wanted to pay, but when he saw the bag of tea stems, he suddenly asked, "You are young, what kind of tea do you drink?"
Lin Zhaoxi yawned, her eyes were bloodshot, but her eyes were still soft and bright: "Uncle, I'm really sleepy."
For some reason, Chen Jianguo suddenly felt that he was going too far.
—
In the morning, the small garage.
Lin Zhaoxi unwrapped the tea leaves and brewed a mug full of strong tea. She put the tea mug next to the computer, took out an algorithm book at hand, and read it.
Chen Jianguo followed the girl into the room, and was attracted by the computer screen at first glance.
Although he doesn't know what it is, it seems to be just a simple program, with a lot of codes, as if it is constantly calculating, and some new results will appear.
The girl looked up at the screen from time to time, tapped the keyboard briefly and skillfully, and the program continued to run.
Chen Jianguo stared straight at it.
Suddenly, the small garage fell silent. When Chen Jianguo looked up, he saw his son looking at him with "Why are you still not leaving?"
Chen Jianguo coughed: "Chaoxi, is there anything else I need uncle to help with?"
As soon as he finished speaking, Lin Zhaoxi suddenly raised her head and smiled slyly at him: "That's great, then I'll trouble uncle."
In this way, another half an hour passed.
Sitting in the small garage of his home, Chen Jianguo watched Lin Zhaoxi drink three teacups of water, and listened to the sound of his son typing on the keyboard and flipping through books from time to time.
The outside of the garage became a little lively, the elderly went out of the house to meet to buy vegetables, and the sleepless children started running around in the yard.
A quilt was exposed to the horizontal bars in the new village. Chen Jianguo felt that at this point, the possibility of thieves coming out to steal the battery car was not great.
He moved left and right, looked at the children on both sides who were buried in their studies, and finally couldn't help asking: "Are you sure the thief will come to steal the car this morning?"
"Well, I can't say for sure, I can only say that there is a high probability that it will be today."
"How can this be calculated?"
"Human behavior looks chaotic, but they all have internal patterns." Lin Zhaoxi paused, "Especially criminal behavior. We thought they happened independently, but they didn't. Events are time-related."
Lin Zhaoxi picked up a pen and wrote a long formula on paper: "Using the Hawkes process, we can statistically model the time and frequency of battery car thefts, and then describe them with exact numbers and formulas."
"Huo, what's going on?" Chen Jianguo was at a loss, but the girl suddenly looked outside the garage.
Small-scale uproar started from afar.
At first, I didn't know which family was looking for something, and then there was a quarrel between husband and wife blaming each other. Not long after, the whole community knew that in order to steal the electricity charging bottle in the corridor, the old Wang of the 7th building did not lock the car in the garage, so the car was stolen.
Chen Zhu stood up and walked out with his notebook and small mobile phone. Instead, Lin Zhaoxi sat in front of the computer, closed the book, and started looking at the screen.
Chen Jianguo hurried out with his son.
When Chen Zhu arrived at the scene, he had the airs of the traffic police investigating traffic accidents. He began to ask about the brand and model of the stolen battery car.
"We don't know the model and brand of the broken car. We bought it a long time ago." The woman said.
"How many years?" Chen Zhu asked again, "Have you changed the battery?"
When Chen Jianguo saw the woman cast a strange glance at his son, he couldn't help asking, "What does the lost car look like, do you have a picture?"
The woman started flipping through her phone while muttering about the photos of the broken battery car.
Not long after, she found a photo of riding a bike with her son.
At this moment, Building No. 8, next to Building No. 7, also wailed dryly: "The thief with no conscience! I just replaced the new battery the day before yesterday!!!"
Chen Zhu put away his notes and went to Building 8 again. It seems that the thief not only stole Lao Wang's battery car, but also took Lao Zhang's battery.
The battery car without the battery is just an iron frame with a big hole in the middle, which looks very intrusive.
Chen Zhu carefully looked at the model of the battery car, took two photos, and ran back to the garage, followed by Chen Jianguo.
In the garage, Lin Zhaoxi has opened a huge excel document, which contains dense data of battery cars, vehicle models, driving speeds, etc.
Chen Zhu showed the photos of the scene, and the two children studied for a while and determined several values.
Next, he saw them call out the road map they had prepared. There are many dense signal lights and roads on it, which are given different values, which looks chaotic.
Lin Zhaoxi and Chen Zhu studied for a while, determined a few lines, and began typing codes into the program.
Chen Jianguo was puzzled again: "But how do you determine when the thief stole the car? This can also be counted?"
"It's difficult to calculate, so we installed surveillance cameras in the southeast, north and south of the community."
The girl's voice was understated, and she pointed to Chen Zhu's position. Chen Jianguo ran over and saw his son dragging and dropping the timeline of the surveillance video, and almost choked on his own saliva.
In order to catch thieves, they even specially installed surveillance cameras. These kids are too outrageous!
"There is still a route, how did you determine it?" Chen Jianguo held back his surprise and continued to ask.
"We have investigated a lot of news and the second-hand car recycling market. After a thief steals a car, there are two ways to sell the stolen goods. The first is to sell it directly, and the second is to change it and sell it again."
Chen Zhu said confidently, "No matter what method of selling stolen goods, it will take a certain amount of time to go from the point of theft to the den of selling stolen goods. Using constrained optimization, we can find the best selling place suitable for the stolen battery cars in our Aimin community."
"So... you guys did all of this?" Chen Jianguo was shocked.
"She did it." Chen Zhu pointed to the girl who took a sip of tea in front of the computer and said.
Lin Zhaoxi raised her head, tapped her forehead with her index and middle fingers together, and greeted him with a smile.
Chen Jianguo didn't know what constrained optimization refers to. He only saw that the simple program on the monitor began to calculate rapidly, line after line of code poured down, and at a certain point, it suddenly stopped.
A popup appears.
It was a map of their area, with three red circles on it, indicating three results.
Red Star Crossing 6:41-6:44
Simin Intersection 6:45-6:47
Heping Street 6:51-6:55
The time in the lower right corner of the computer is 6:45, Hongxing intersection and Simin Road are basically too late, and it takes them at least seven or eight minutes to ride normally to Heping Street intersection.
"Trouble uncle." The girl turned her head, her eyes bright and firm.
Without saying a word, Chen Jianguo turned around and ran away.
He rode on the motorcycle, put on his helmet, started the engine, and the police rushed forward with a bang.
The strong wind blew past his ears, and the street scene was reversed. Chen Jianguo felt that he hadn't been this crazy for a long time in his age.
If you can catch it, that would be amazing.
Chen Jianguo thought excitedly.
—
Heping Street.
The motorcycle slammed to a halt, making a screeching sound. Chen Jianguo jumped off the motorcycle, glanced at his watch, and there was still time.
It was 6:52 and he began to watch nervously.
At the end of autumn and early winter, it is still light after six o'clock.
Heping Street is not a main road, and there are even fewer pedestrians. If a car with a battery on a battery scooter passes by, it is easy to spot.
He stared, breathlessly, and began to wait.
An old man riding a bicycle, an aunt shopping for vegetables, a young man with his girlfriend...
—
Five minutes passed.
Ten minutes passed.
The sky is getting brighter and brighter, gradually changing from indigo to transparent, the intersection is getting busier, and Chen Jianguo is getting brighter.
Finally, his cell phone rang.
"Uncle Chen." On the other end of the phone, the girl's voice was calm, "Did you see the thief?"
"I didn't see it." Chen Jianguo paused, then looked towards the intersection, "Maybe uncle didn't get there in time."
"It's not uncle's problem, or the program's calculations are not accurate enough."
Holding the phone, Chen Jianguo could almost imagine Lin Zhaoxi's frustrated face. He hurriedly said, "Don't be discouraged, uncle thinks you are already very good."
"Is uncle comforting me?"
"It's not consolation, it's encouragement..."
"Then uncle, can you take me to the traffic police detachment to see the monitoring at this time, and continue to encourage me?"
On the other end of the phone, the girl asked.
—
The little girl's voice was crisp and not at all low, but because of this, Chen Jianguo just couldn't refuse.
He brought a son and a daughter into the team, tuned the video, and was teased by his colleagues that he had both children, so he found a reason to perfunctory.
"Old Chen, which time slot do you want to watch?"
Lin Zhaoxi didn't speak, Chen Jianguo stood behind the monitor and reported the intersections and time he had just memorized.
After he said this, he suddenly realized that the results calculated by the program were all intercept points from the alley to the intersection that avoided the surveillance, which was really amazing.
Drag the time axis, and the screen of Heping Street will first be displayed on the monitor.
Chen Jianguo was still thinking, if the thief really didn't leave Heping Street, he would continue to check the remaining two points.
While he was still making plans, a pink battery car drove slowly past the intersection.
The left pedal fell off, and there was a group of rats on the car body.
Sure enough, it was the car lost by the old Wang's family. The monitoring showed that the time was 6:51:03 seconds. About 1 minute later, he appeared on a motorcycle.
"Oh, it's so close!" Chen Jianguo shouted.