• bastion@feddit.nl
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      16 hours ago

      The alignment of the language and the alignment of the coder must be similar on at least one metric, or the coder suffers a penalty to develop for each degree of difference from the language’s alignment. This is penalty stacks for each phase of the project.

      So, let’s say that the developer is a lawful good Rust zealot Paladin, but she’s developing in Python, a language she’s moderately familiar with. Since Python is neutral/good, she suffers a -1 penalty for the first phase, -2 for the second, -3 for the third, etc. This is because Rust (the Paladin’s native language) is lawful, and Python is neutral (one degree of difference from lawful), so she operates at a slight disadvantage. However, they are both “good”, so there’s no further penalty.

      The same penalty would occur if using C, which is lawful neutral - but the axis of order and chaos matches, and there is one degree of difference on the axis of good and evil.

      However, if that same developer were to code in Javascript (chaotic neutral), it would be at a -3 (-6, -9…) disadvantage, due to 2 and 1 degree of difference in alignment, respectively.

      Malbolge (chaotic evil), however, would be a -4 (-8, -12) plus an inherent -2 for poor toolchain availability.

      …hope this helps. have fun out there!

  • mavu@discuss.tchncs.de
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    2 days ago

    This reminds me that I actually once made a class to store bools packed in uint8 array to save bytes.

    Had forgotten that. I think i have to update the list of top 10 dumbest things i ever did.

  • elucubra@sopuli.xyz
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    2 days ago

    Could a kind soul ELI5 this? Well, maybe ELI8. I did quite a bit of programming in the 90-00s as part of my job, although nowadays I’m more of a script kiddie.

    • superheitmann@programming.dev
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      1 day ago

      A Boolean is a true/false value. It can only be those two values and there be represented by a single bit (1 or 0).

      In most languages a Boolean variable occupies the space of a full byte (8 bit) even though only a single of those bits is needed for representing the Boolean.

      That’s mostly because computers can’t load a bit. They can only load bytes. Your memory is a single space where each byte has a numeric address. Starting from 0 and going to whatever amount of memory you have available. This is not really true because on most operating systems each process gets a virtual memory space but its true for many microcontrollers. You can load and address each f these bytes but it will always be a byte. That’s why booleans are stored as bytes because youd have to pack them with other data on the same address other wise and that’s getting complicated.

      Talking about getting complicated, in C++ a std::vector<bool> is specialized as a bit field. Each of the values in that vector only occupy a single bit and you can get a vector of size 8 in a single byte. This becomes problematic when you want to store references or pointers to one of the elements or when you’re working with them in a loop because the elements are not of type bool but some bool-reference type.

  • acockworkorange@mander.xyz
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    2 days ago

    In the industrial automation world and most of the IT industry, data is aligned to the nearest word. Depending on architecture, that’s usually either 16, 32, or 64 bits. And that’s the space a single Boolean takes.

    • ZILtoid1991@lemmy.world
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      2 days ago

      That’s why I primarily use booleans in return parameters, beyond that I’ll try to use bitfields. My game engine’s tilemap format uses a 32 bit struct, with 16 bit selecting the tile, 12 bit selecting the palette, and 4 bit used for various bitflags (horizontal and vertical mirroring, X-Y axis invert, and priority bit).

      • acockworkorange@mander.xyz
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        2 days ago

        Bit fields are a necessity in low level networking too.

        They’re incredibly useful, I wish more people made use of them.

        I remember I interned at a startup programming microcontrollers once and created a few bitfields to deal with something. Then the lead engineer went ahead and changed them to masked ints. Because. The most aggravating thing is that an int size isn’t consistent across platforms, so if they were ever to change platforms to a different word length, they’d be fucked as their code was full of platform specific shenanigans like that.

        /rant

  • skisnow@lemmy.ca
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    3 days ago

    Back in the day when it mattered, we did it like

    #define BV00		(1 <<  0)
    #define BV01		(1 <<  1)
    #define BV02		(1 <<  2)
    #define BV03		(1 <<  3)
    ...etc
    
    #define IS_SET(flag, bit)	((flag) & (bit))
    #define SET_BIT(var, bit)	((var) |= (bit))
    #define REMOVE_BIT(var, bit)	((var) &= ~(bit))
    #define TOGGLE_BIT(var, bit)	((var) ^= (bit))
    
    ....then...
    #define MY_FIRST_BOOLEAN BV00
    SET_BIT(myFlags, MY_FIRST_BOOLEAN)
    
    
    • Quatlicopatlix@feddit.org
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      2 days ago

      With embedded stuff its still done like that. And if you go from the arduino functionss to writing the registers directly its a hell of a lot faster.

    • ethancedwards8@programming.dev
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      2 days ago

      Okay. Gen z programmer here. Can you explain this black magic? I see it all the time in kernel code but I have no idea what it means.

      • skisnow@lemmy.ca
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        The code is a set of preprocessor macros to stuff loads of booleans into one int (or similar), in this case named ‘myFlags’. The preprocessor is a simple (some argue too simple) step at the start of compilation that modifies the source code on its way to the real compiler by substituting #defines, prepending #include’d files, etc.

        If myFlags is equal to, e.g. 67, that’s 01000011, meaning that BV00, BV01, and BV07 are all TRUE and the others are FALSE.

        The first part is just for convenience and readability. BV00 represents the 0th bit, BV01 is the first etc. (1 << 3) means 00000001, bit shifted left three times so it becomes 00001000 (aka 8).

        The middle chunk defines macros to make bit operations more human-readable.

        SET_BIT(myFlags, MY_FIRST_BOOLEAN) gets turned into ((myFlags) |= ((1 << 0))) , which could be simplified as myFlags = myFlags | 00000001 . (Ignore the flood of parentheses, they’re there for safety due to the loaded shotgun nature of the preprocessor.)

      • NιƙƙιDιɱҽʂ@lemmy.world
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        2 days ago

        It’s called bitshifting and is used to select which bits you want to modify so you can toggle them individually.

        1 << 0 is the flag for the first bit
        1 << 1 for the second
        1 << 2 for the third and so on

        I think that’s correct. It’s been years since I’ve used this technique tbh 😅

    • excral@feddit.org
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      2 days ago

      In terms of memory usage it’s a waste. But in terms of performance you’re absolutely correct. It’s generally far more efficient to check is a word is 0 than to check if a single bit is zero.

  • KindaABigDyl@programming.dev
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    3 days ago
    typedef struct {
        bool a: 1;
        bool b: 1;
        bool c: 1;
        bool d: 1;
        bool e: 1;
        bool f: 1;
        bool g: 1;
        bool h: 1;
    } __attribute__((__packed__)) not_if_you_have_enough_booleans_t;
    
    • xthexder@l.sw0.com
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      3 days ago

      Or just std::bitset<8> for C++. Bit fields are neat though, it can store weird stuff like a 3 bit integer, packed next to booleans

    • h4x0r@lemmy.dbzer0.com
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      3 days ago

      This was gonna be my response to OP so I’ll offer an alternative approach instead:

      typedef enum flags_e : unsigned char {
        F_1 = (1 << 0),
        F_2 = (1 << 1),
        F_3 = (1 << 2),
        F_4 = (1 << 3),
        F_5 = (1 << 4),
        F_6 = (1 << 5),
        F_7 = (1 << 6),
        F_8 = (1 << 7),
      } Flags;
      
      int main(void) {
        Flags f = F_1 | F_3 | F_5;
        if (f & F_1 && f & F_3) {
          // do F_1 and F_3 stuff
        }
      }
      
      • anotherandrew@lemmy.mixdown.ca
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        2 days ago

        Why not if (f & (F_1 | F_3)) {? I use this all the time in embedded code.

        edit: never mind; you’re checking for both flags. I’d probably use (f & (F_1 | F_3)) == (F_1 | F_3) but that’s not much different than what you wrote.

    • mmddmm@lemm.ee
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      3 days ago

      And compiler. And hardware architecture. And optimization flags.

      As usual, it’s some developer that knows little enough to think the walls they see around enclose the entire world.

      • timhh@programming.dev
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        2 days ago

        I don’t think so. Apart from dynamically typed languages which need to store the type with the value, it’s always 1 byte, and that doesn’t depend on architecture (excluding ancient or exotic architectures) or optimisation flags.

        Which language/architecture/flags would not store a bool in 1 byte?

        • brian@programming.dev
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          2 days ago

          things that store it as word size for alignment purposes (most common afaik), things that pack multiple books into one byte (normally only things like bool sequences/structs), etc

        • mmddmm@lemm.ee
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          2 days ago

          Apart from dynamically typed languages which need to store the type with the value

          You know that depending on what your code does, the same C that people are talking upthread doesn’t even need to allocate memory to store a variable, right?

    • Anders429@programming.dev
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      2 days ago

      It would be slower to read the value if you had to also do bitwise operations to get the value.

      But you can also define your own bitfield types to store booleans packed together if you really need to. I would much rather that than have the compiler do it automatically for me.

    • timhh@programming.dev
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      2 days ago

      Well there are containers that store booleans in single bits (e.g. std::vector<bool> - which was famously a big mistake).

      But in the general case you don’t want that because it would be slower.

    • gamer@lemm.ee
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      2 days ago

      Consider what the disassembly would look like. There’s no fast way to do it.

      It’s also unnecessary since 8 bytes is a negligible amount in most cases. Serialization is the only real scenario where it matters. (Edit: and embedded)

      • Croquette@sh.itjust.works
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        2 days ago

        In embedded, if you are to the point that you need to optimize the bools to reduce the footprint, you fucked up sizing your mcu.

  • Lucy :3@feddit.org
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    3 days ago

    Then you need to ask yourself: Performance or memory efficiency? Is it worth the extra cycles and instructions to put 8 bools in one byte and & 0x bitmask the relevant one?

    • Nat (she/they)
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      3 days ago

      A lot of times using less memory is actually better for performance because the main bottleneck is memory bandwidth or latency.

      • Cethin@lemmy.zip
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        3 days ago

        Yep, and anding with a bit ask is incredibly fast to process, so it’s not a big issue for performance.

      • timhh@programming.dev
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        2 days ago

        It’s not just less memory though - it might also introduce spurious data dependencies, e.g. to store a bit you now need to also read the old value of the byte that it’s in.

        • Nat (she/they)
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          1 day ago

          Could definitely be worse for latency in particular cases, but if we imagine a write heavy workload it still might win. Writing a byte/word basically has to do the same thing: read, modify write of cache lines, it just doesn’t confuse the dependency tracking quite as much. So rather than stalling on a read, I think that would end up stalling on store buffers. Writing to bits usually means less memory, and thus less memory to read in that read-modify-write part, so it might still be faster.

        • anton
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          2 days ago

          It might also introduce spurious data dependencies

          Those need to be in the in smallest cache or a register anyway. If they are in registers, a modern, instruction reordering CPU will deal with that fine.

          to store a bit you now need to also read the old value of the byte that it’s in.

          Many architectures read the cache line on write-miss.

          The only cases I can see, where byte sized bools seems better, are either using so few that all fit in one chache line anyways (in which case the performance will be great either way) or if you are repeatedly accessing a bitvector from multiple threads, in which case you should make sure that’s actually what you want to be doing.