World: r4wp
[#Red] Red language group
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Kaj 23-Dec-2012 [4799x2] | Use :cpu-count :len |
What does len specify? | |
Jerry 23-Dec-2012 [4801] | len ... the length of buffer in the next parameter??? not sure. |
DocKimbel 24-Dec-2012 [4802] | From Announce: Great Kaj! The optimizer should be able to do a pretty good job on simple cases like Fibonacci function. Still, you'll have the Red stack management overhead, which is currently unavoidable, but in the future, we might found ways to optimize it too. Actually, I have two options to reduce stack overhead: stack multiple openings/closing compression and inlining stack calls, but we'll see that in Red v2. |
Jerry 25-Dec-2012 [4803] | Red/System Questions: I am translating a piece of code from C to Red/System, I don't know how to translate the following C code: success = OSAtomicCompareAndSwapPtrBarrier(NULL, newzone, (void * volatile *)&_zone_); // C my problems are: 1. In Red/Sys, _sqliteZone_ is a struct! (which is a pointer in Red/Sys), so I cannot use :_zone_ to get it's address. 2. "(void * volatile *)" in C => "as byte-ptr!" in Red/Sys ?? Thanks! |
DocKimbel 25-Dec-2012 [4804] | 1) Is _zone_ a struct or a struct pointer? If it is a struct, then in Red/System, you just pass the struct! variable. 2) Correct, use "as byte-ptr!" in such case. |
Jerry 25-Dec-2012 [4805] | 1. _zone_ is a struct pointer. I need to pass a pointer to a struct pointer as the 3rd parameter, that's why I try to use get-word here. |
DocKimbel 25-Dec-2012 [4806] | For 1., you can achieve it this way: s: declare struct! [n [integer!]] p: declare int-ptr! p/value: as-integer s then `p` becomes a pointer on `s`. I might extend get-word syntax to struct! and pointer! too, someone just needs to add a ticket to Github to remind me of that. |
Jerry 25-Dec-2012 [4807] | Thanks, Doc |
Kaj 25-Dec-2012 [4808x5] | I usually solve such double references by wrapping the needed pointer in an extra struct. See the *-reference! types here: |
http://red.esperconsultancy.nl/Red-common/artifact/aad3c29d7fb6647bb1e5d8b404d05211f5ed33c1 | |
Speaking about atomic operations, any thought to get them in Red/System? I could use them well | |
Perhaps an atomic! type for an integer with guarantees about the generated code? | |
What are the chances that current integer operations already have atomic behaviour? | |
DocKimbel 25-Dec-2012 [4813x3] | I'm not sure what you mean by "atomic operation"? |
Red/System integer! operations are as atomic as the CPU permits. | |
Red/System maps its datatypes as closely as possible to the CPU (the same way C does). | |
Andreas 25-Dec-2012 [4816] | Re atomic operation: atomic "x: x + 1", for example. |
Kaj 25-Dec-2012 [4817x3] | Atomic means safe from corruptions by other CPU cores accessing the same memory |
http://syllable.cvs.sourceforge.net/viewvc/syllable/syllable/system/sys/include/atheos/atomic.h?view=markup | |
These become vital when you start doing multi-core concurrency | |
DocKimbel 25-Dec-2012 [4820] | Ok, I see what you mean. Like in C, you can already write "thread-safe" code in Red/System by using only variables on stack. If you need concurrent access to global variables, usually, the OS are already providing some API for that (locks, semaphores, mutex,...). I haven't chosen yet how it will be implemented at Red/System level, there are different options. For example, it could be handled by the language directly using a similar construct as in Java: synchronize [ x: x + 1 ] In my early design notes, I have researched only how to handle concurrency at Red level, I've left the underlying Red/System part as an "implementation detail". I plan to start working on it after I/O will be implemented. |
Kaj 25-Dec-2012 [4821x2] | I'm thinking about the case where you want to implement operating system level code yourself. For example, I have been fixing many bugs in Syllable's PThreads implementation, but I would like to replace it with a Red/System implementation. PThreads adds quite a few constructs that Syllable's kernel primitives don't implement as such, so to add them you need to write extra concurrency code |
For example, there are spinlock-like constructions in Syllable's PThreads implementation that can often prevent having to call a kernel mutex. This makes them much more efficient, but you need atomic operations on access flags and counters to implement the user-space spinlocks and mutex shells | |
DocKimbel 25-Dec-2012 [4823] | Modern CPU usually provide a way to make such atomic operations (e.g. CAS-type instructions), Red/System might provide access to them if it is required. |
Kaj 25-Dec-2012 [4824] | Something like that is what I have in mind. From what CPUs on are they supported? |
DocKimbel 25-Dec-2012 [4825] | From a quick googling, I've found: - x86: CMPXCHG (compare and exchange) is supported from 486. LOCK instruction seems to be available from PentiumPro only. - ARM: Starting with the ARMv6 architecture ARM has the LDREX/STREX instructions that can be used to implement an atomic compare-exchange operation. |
Kaj 25-Dec-2012 [4826x2] | So it would bump Red's requirements a little, but I guess it's worth it |
http://en.wikipedia.org/wiki/Compare-and-swap | |
Jerry 25-Dec-2012 [4828x2] | In current Red/System, there is no break/continue keywords (for loop), I wish they will show up in Red/System 2.0 |
So how can I break/continue a loop now? | |
DocKimbel 25-Dec-2012 [4830x2] | BREAK will probably be implemented before 2.0 (not sure for CONTINUE). So, you can't break from a loop currently. As a workaround, you can EXIT/RETURN instead. So if you write your loop in a separate function, you'll get similar effect as with BREAK. |
I'm a bit late for the Xmas release, sorry...still fixing bugs... | |
Kaj 25-Dec-2012 [4832] | I thought we already had a Xmas release :-) |
DocKimbel 25-Dec-2012 [4833x3] | Actually, it is not really a new release, as I did too many changes and it would need a week at least to stabilize and fully complete. But it will be a significant revision. ;-) |
revision = commit | |
I've stressed the current Red runtime source code a bit so it keeps "tilting" as I try to make it work. :-) | |
Jerry 25-Dec-2012 [4836] | Doc, will you spend some time making Red/Sys support loop BREAK/CONTINUE in the near future? or at least GOTO. Thanks. Programming without them is like drinking soup without a spoon ... |
DocKimbel 26-Dec-2012 [4837] | BREAK is on my todo list. I might add CONTINUE too. GOTO could be useful for implementing fast FSM, but having some specific feature for FSM support would probably be a cleaner option than GOTO. I personally very rarely need BREAK/CONTINUE, their usage depends on your programming style and the way you implement algorithms. |
Arnold 26-Dec-2012 [4838] | There are many way in which break and continue are being used amongst the different programming languages, most notable in case or switch statements. |
DocKimbel 26-Dec-2012 [4839x3] | BREAK in CASE/SWITCH statement is IMHO a very bad design choice leading to countless bugs. I'm glad Red and REBOL are doing it the right way. |
Xmas feature teaser: http://t.co/jTYwNzfb | |
Implementing that feature revealed a few deep bugs in the current Red runtime code, I hope to be able to finish fixing them by tonight. | |
Henrik 26-Dec-2012 [4842] | great stuff :-) |
Endo 26-Dec-2012 [4843] | Console support! I'm waiting for it impatiently!! BREAK/CONTINUE: I had to use those a few times in REBOL, it would be nice to have CONTINUE in Red too. |
NickA 26-Dec-2012 [4844] | Awesome Doc! Didn't expect to see a console so early. |
DocKimbel 26-Dec-2012 [4845x3] | It's a full REPL, so it's an interpreter + console. I was thinking about adding an interpreter since this summer in order to fill the gaps until the JIT-compiler will be there. Even when Red will gain JIT-compilation ability, for dynamic code with no loops, interpreting the code will be faster. Also, on some platforms, JIT-compilation is not allowed, so the interpreter will be handy to workaround those limitations. |
Now, you have a better picture about the "full-stack" approach of Red language. :-) | |
The console is currently just a Red script, once we get devices and ports, it will be replaced by a proper console:// port. | |
NickA 26-Dec-2012 [4848] | This will make it much easier for everyone to pick it up and experiment quickly and easily. |
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