unrolling loops is efficient, right?

Comments

• ImplyingImplications@lemmy.ca ⁨1⁩ ⁨year⁩ ago

  “CS Major” is one of my favourite memes

  Image

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  • tool@r.rosettast0ned.com ⁨1⁩ ⁨year⁩ ago

    It’s so rare for me to have to use the modulo operator I’m actually excited when I come across a situation where I can.

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    • jimmux@programming.dev ⁨1⁩ ⁨year⁩ ago

      It’s like how when you were a kid, you thought quicksand was something you would need to be aware of as an adult in the big wide world. In my undergrad, mod everywhere. Very important knowledge. Now not so much.

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    • evatronic@lemm.ee ⁨1⁩ ⁨year⁩ ago

      I did it the other day!

      I was trying to pad a base64-encoded string with the proper number of =s to get it up to a multiple of 4 because our stupid build toolchain would explode if it wasn’t.

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  • chandz05@lemmy.world ⁨1⁩ ⁨year⁩ ago

    Wow I literally laughed out loud

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  • kungfusion@kbin.social ⁨1⁩ ⁨year⁩ ago

    i logged in to upvote you, thank you

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• potoo22@programming.dev ⁨1⁩ ⁨year⁩ ago

  In my first CS class, the professor announced an extra credit project due at the end of the class. It was to create a formatted terminal calendar given a year from user input. I finished it after learning about condition but before I learned about classes… or functions… or loops… or searching the internet… partially. I searched how leap years worked, but didn’t bother to search for code.

  Anyway, long ass program with each month hard-coded with 7 possible calendars for each month depending on the first day of the week. Lots of copy and paste. Professor was speechless, but accepted it.

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  • ICastFist@programming.dev ⁨1⁩ ⁨year⁩ ago

    “It’s not stupid if it works”

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• coloredgrayscale@programming.dev ⁨1⁩ ⁨year⁩ ago

  300 nested if statements, (…) added another 5000 nested if statements.

  At this point I want to doubt that they actually wrote it themselves, vs writing a metaprogram to generate the code. >>>

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  • sukhmel@programming.dev ⁨1⁩ ⁨year⁩ ago

    Not sure if that would’ve made it better or worse 🤔

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  • nintendiator@feddit.cl ⁨1⁩ ⁨year⁩ ago

    Oh, a metaprogram?

    ifs printing ifs…

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• selawdivad@lemm.ee ⁨1⁩ ⁨year⁩ ago

  One of the first real programs I wrote was a program to display telemetry data from a CAN bus. I was on the solar car team at uni, and we wanted to be able to view the data from the various systems live during the race. The CAN network was connected to a CAN-ethernet converter, which sent UDP packets over a wireless ethernet link to our lead car. I had no experience with networking, or UDP or CAN at all, but I had some documentation and a lot of free time, so I got to work.

  Each device on the CAN network had a bit mask to identify it. For example, the bit mask for the motor controller might have been 0x1200. This meant that any packet starting with 0x12 belonged to the motor controller. For example, 0x1201 was one type of message, and 0x1202 another type, but both belonged to the motor controller.

  There was specific logic for each device on the network, so you needed to first figure out which device owned a packet using the bit mask, then apply the relevant logic to decode the packet.

  Looking back, I realise the correct way to approach this would be to have a list of bit masks:

  0x1200
  0x1300
  0x1400
  

  Then simply bitwise & any incoming packet with 0xff00, and lookup the result in the list of bit masks.

  Not knowing better however, what I actually did was create a giant dictionary of every possible packet value, so I could lookup any packet and determine which system it came from. This was so repetitive that I had to make use of my newfound super-power – vim macros – to complete the 8000 line dictionary…

  Excerpt from real code below:

  {
      0x102:
      {
          'name':             'SHUNT_CMU_STATUS_TEMPERATURE_AND_VOLTAGE_1_2',
          'data':
          [
              'cell_0_voltage',
              'cell_1_voltage',
              'cell_2_voltage',
              'cell_3_voltage',
          ],
          'unpack_string':    'intle:16, intle:16, intle:16, intle:16'
      },
  
      0x103:
      {
          'name':             'SHUNT_CMU_STATUS_TEMPERATURE_AND_VOLTAGE_1_3',
          'data':
          [
              'cell_4_voltage',
              'cell_5_voltage',
              'cell_6_voltage',
              'cell_7_voltage',
          ],
          'unpack_string':    'intle:16, intle:16, intle:16, intle:16'
      },
  }
  

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  • Karyoplasma@discuss.tchncs.de ⁨1⁩ ⁨year⁩ ago

    If it works, it works. Let your successor worry about maintainabilty.

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    • selawdivad@lemm.ee ⁨1⁩ ⁨year⁩ ago

      It worked, but it was slow and dropped packets sometimes. I think the next team switched to Java. I met with them and walked them through the code and suggested they try a different approach. Hopefully they did!

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