5 ms·

I don't get you. Is not C high-level?

by asmman1 13y ago

stass 13y ago
No, C is as low level as you can get. It directly maps into the instructions of a register machine in runs on.
- gcr 13y ago
  Assembly directly maps into machine instructions. The mapping between C and assembly is very nontrivial, and is definitely not one-to-one.
- sillysaurus2 13y ago
  I invite anyone who thinks C is low level to try their hand at CUDA or OpenCL. You think C is bad? Those are far worse. This is at least a great step in the right direction. It's not "low level" as you describe just because it's C.
  - foxhill 13y ago
    i will preface this by saying i'm a C programmer at heart, CUDA and OpenCL demand a depth of understanding of both C, and how your code is executed on many core processors. but i wouldn't call either of them terrible. i would however, very much like to see a widespread higher level API for doing compute on GPUs, if only to encourage people to understand the lower level details.
  - rbonvall 13y ago
    You know what's worse than CUDA or OpenCL? General purpose algorithms implemented in a graphics API. I read a lot of GPGPU papers at the university, and I could never understand the older ones, that described algorithms by mapping everything to graphics elements, and computed the solutions as a side-effect of rendering something. Next to that, undestanding an algorithm implemented in CUDA is a breeze.
  - stass 13y ago
    I didn't say at all that C is bad, as a matter of fact I write most of my code in C. It is, however a low-level programming language not much different from assembly. The reason it is that it operates on concepts that are not abstract but are of register machines. A high completely abstracts underlying architecture so the code can be executed in any possible environment by means of translation, be it a $10MM Cray or a cellular automaton or a mechanical computer. In essence, a high level language provides an abstract notation for computation. C, however, is not abstract at all. Variables? How those will map to a dataflow computation? Pointers? Would not work beyond register CPUs (e.g. it is very cumbersome to translate C programs to Javascript as a result and usually leads to a memory array emulation). Fixed-width types? Volatile pointers? Returns from the middle of a procedure? Gotos? Come on, how those are even going to run on a non-conventional architecture? C also does not completely define the language semantics leaving certain operations implementation-specific or undefined. It also (before C11) didn't define any memory model, thus making it impossible to even describe an algorithm that depends on specific properties of memory accesses in a way that will be portable across different register machines. C algorithms are close to impossible to translate to be run on memory-less computation devices as the whole concept of C is based around having local memory and a stack space with certain properties (unless one wants to emulate a register machine, see JavaScript remark above). In certain areas it lead to some ugly solutions like Cuda where the language looks like C but semantics is completely different and GPUs are the closest thing to he original C target as you can get.
- foxhill 13y ago
  C is no where near as low level as you can get. C-- is closer. LLVM-IR is even closer. but really, the lowest level you can get is the assembly of the architecture you're running on. at the time of the creation, the general consensus was that C was too high level, that it abstracted away the actual workings of the code. we've been introduced to high level languages that have made us re-evaluate what it means to be low or high level. but make no mistake, C is.. at least medium-level..!
  - mgraczyk 13y ago
    At the risk of being pointlessly pedantic: assembly is surely not the lowest level relevant to the topic at hand. When programming for very high performance, you usually need to consider the microarchitecture you are targeting.
    - gcr 13y ago
      Hmm. Most "super-high-performance" projects I've seen find they can get more bang for the buck by switching to a different microarchitecture (FPGA etc) or exploiting parallelism (buy ten computers), not so much optimizing the machine code.
  - mgraczyk 13y ago
    At the risk of being pointlessly pedantic: assembly is surely not the lowest level relevant to the topic at hand. When programming for very high performance, you usually need to consider the microarchitecture you are targeting.

I don't get you. Is not C high-level?

by asmman1 13y ago

I don't get you. Is not C high-level?

stass 13y ago

No, C is as low level as you can get. It directly maps into the instructions of a register machine in runs on.

gcr 13y ago
Assembly directly maps into machine instructions. The mapping between C and assembly is very nontrivial, and is definitely not one-to-one.
sillysaurus2 13y ago
I invite anyone who thinks C is low level to try their hand at CUDA or OpenCL. You think C is bad? Those are far worse. This is at least a great step in the right direction. It's not "low level" as you describe just because it's C.
- foxhill 13y ago
  i will preface this by saying i'm a C programmer at heart, CUDA and OpenCL demand a depth of understanding of both C, and how your code is executed on many core processors. but i wouldn't call either of them terrible. i would however, very much like to see a widespread higher level API for doing compute on GPUs, if only to encourage people to understand the lower level details.
- rbonvall 13y ago
  You know what's worse than CUDA or OpenCL? General purpose algorithms implemented in a graphics API. I read a lot of GPGPU papers at the university, and I could never understand the older ones, that described algorithms by mapping everything to graphics elements, and computed the solutions as a side-effect of rendering something. Next to that, undestanding an algorithm implemented in CUDA is a breeze.
- stass 13y ago
  I didn't say at all that C is bad, as a matter of fact I write most of my code in C. It is, however a low-level programming language not much different from assembly. The reason it is that it operates on concepts that are not abstract but are of register machines. A high completely abstracts underlying architecture so the code can be executed in any possible environment by means of translation, be it a $10MM Cray or a cellular automaton or a mechanical computer. In essence, a high level language provides an abstract notation for computation. C, however, is not abstract at all. Variables? How those will map to a dataflow computation? Pointers? Would not work beyond register CPUs (e.g. it is very cumbersome to translate C programs to Javascript as a result and usually leads to a memory array emulation). Fixed-width types? Volatile pointers? Returns from the middle of a procedure? Gotos? Come on, how those are even going to run on a non-conventional architecture? C also does not completely define the language semantics leaving certain operations implementation-specific or undefined. It also (before C11) didn't define any memory model, thus making it impossible to even describe an algorithm that depends on specific properties of memory accesses in a way that will be portable across different register machines. C algorithms are close to impossible to translate to be run on memory-less computation devices as the whole concept of C is based around having local memory and a stack space with certain properties (unless one wants to emulate a register machine, see JavaScript remark above). In certain areas it lead to some ugly solutions like Cuda where the language looks like C but semantics is completely different and GPUs are the closest thing to he original C target as you can get.
foxhill 13y ago
C is no where near as low level as you can get. C-- is closer. LLVM-IR is even closer. but really, the lowest level you can get is the assembly of the architecture you're running on. at the time of the creation, the general consensus was that C was too high level, that it abstracted away the actual workings of the code. we've been introduced to high level languages that have made us re-evaluate what it means to be low or high level. but make no mistake, C is.. at least medium-level..!
- mgraczyk 13y ago
  At the risk of being pointlessly pedantic: assembly is surely not the lowest level relevant to the topic at hand. When programming for very high performance, you usually need to consider the microarchitecture you are targeting.
  - gcr 13y ago
    Hmm. Most "super-high-performance" projects I've seen find they can get more bang for the buck by switching to a different microarchitecture (FPGA etc) or exploiting parallelism (buy ten computers), not so much optimizing the machine code.
- mgraczyk 13y ago
  At the risk of being pointlessly pedantic: assembly is surely not the lowest level relevant to the topic at hand. When programming for very high performance, you usually need to consider the microarchitecture you are targeting.