Split from A plea for int overflow checking as the default - #63 by Jean_Michel I am not sure this would be significantly better in the current state of the compiler. I haven’t looked into the implementation of BigInt, but just from poking around: AU=Union{Int, BigInt}[1, BigInt(-1)] pt = reinte…

[image] A plea for int overflow checking as the default I guess I would prefer it to throw instead of segfaulting There’s a good reason we never allow code like the above into Base and strongly discourage calling pointer. For the past couple version, it can be replaced with Ref in almost all c…

[image] A plea for int overflow checking as the default It is likely well-past time for the pointer function to be deprecated and removed, but so far not especially high-priority. No, please, not my pointers! Snippets like the above are invaluable for peeking under the hood and understanding h…

[image] A plea for int overflow checking as the default It is likely well-past time for the pointer function to be deprecated and removed, but so far not especially high-priority. I am rather nervous that deprecating pointers would make some useful things impossible to do in Julia, even in pri…

[image] A plea for int overflow checking as the default I were to actually do this with reinterpret, I would have to allocate an array twice reinterpret doesn’t allocate a new array.

[image] A plea for int overflow checking as the default reinterpret doesn’t allocate a new array. Hm, it certainly seems to be doing that based on performance benchmarks. Like I said, when I get a chance I’m going to make a thread on this and hopefully you can help me :smile:

I think the point of contention here is the following: The array-reinterpret does not allocate new space for the data, but it AFAIK does allocate a new jl_array struct on the heap (ca 1 cache-line), i.e. it is about as allocating as a view or an empty (length==0) array. Whether you can afford to sp…

I also use pointer extensively, to get C performance from Julia. I’ve done extensive benchmarking, and pointers have always given me the best results.

[image] A plea for int overflow checking as the default I also use pointer extensively, to get C performance from Julia. Currently we pessimize (slow down) array-loads in some cases because of the possibility that they may have been used with the (now mostly deprecated implementation of) reint…

[image] A plea for int overflow checking as the default We always pessimize the performance of pointer calls and any code around them. Can you give some concrete examples of that? I’ve found that for the sorts of things I’ve been doing, where I jump between using a Ptr{UInt64} and a Ptr{UInt8…

[image] A plea for int overflow checking as the default Can you give some concrete examples of that? I’m not sure what you mean. Julia defines that pointer / pointer_from_objref returns an invalid Ptr for use from Julia (it can be used from C, although implicit conversion via ccall or Ref shou…

Use of `pointer`

General Usage

stevengj February 3, 2018, 5:36pm 5

reinterpret doesn’t allocate a new array.

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Use of `pointer`

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