Re: [Chicken-users] Best way to share memory between C and Chicken

[Ivan Raikov]

  I think you can try to have native threads by running a separate instance of the Chicken runtime for each thread, but are you sure that you will really achieve a significant speedup over Unix processes and/or MPI?    It's not the early nineties anymore... I suggest prototyping  code and running real-world benchmarks first. But thanks for your efforts on semaphores. I think wrapping the C API is the easy part, you can probably just use c-pointer for the sem_t type. I am guessing the hard part would be ensuring consistent semantics between Unix and the pinnacle of free-market capitalism, Microsoft Windows.

On Sat, May 4, 2013 at 8:39 AM, Dan Leslie <address@hidden> wrote:

Yah, I meant sem_wait et al.

I was under the impression that synch and mailbox rely on srfi-18 structures, which would make them 'green' threads-only and not particularly suitable for multi process synchronization.

Relatedly, is anyone poking at implementing native threads?
I've been digging around a bit but haven't had much time to progress very far.

I'm hesitant to take responsibility for writing a semaphore egg, but what the hell. I'll start something on GitHub this weekend.

-Dan

On 5/3/2013 4:22 PM, Ivan Raikov wrote:

Are you talking about POSIX semaphores, sem_wait(3) and friends, or just the general semaphor data structure? If the former, then the Chicken developers are eagerly awaiting your patches ;-) If the latter, take a look at the synch and mailbox eggs. They have mutex-like functionality that can be used in place of proper semaphores.

  Ivan

On May 4, 2013 7:59 AM, "Dan Leslie" <address@hidden> wrote:

I was just poking through posix, posix-shm, posix-utils, and posix-extras and it seems that none of them implement semaphores!

Am I missing something, or is this actually the case?

-Dan

On 5/3/2013 3:26 PM, Ivan Raikov wrote:

Hello,

  I really strongly advise _against_ using SRFI-4 vectors for 4G files, as I have experienced serious performance issues even with vectors of a few million elements. If  your C code is to be linked with your Chicken code, you can pass the pointer to your data from C to Scheme and use SRFI-4 foreign pointers to access it (see unit lolevel for details). If the C code is running as a separate process, you could try using posix-shm to create shared memory between processes and then use foreign pointers in the Chicken process.

  Ivan

On May 4, 2013 3:04 AM, "Pedro Melendez" <address@hidden> wrote:

Hi all,

Sorry if this question is obvious, but I couldn't find what I were looking for in the documentation so maybe you guys can help me.

I am developing a prototype of a server that would serve 3D seismic images across the network. This  task requires to process big files (~4 GB) with existing C code that is desirable to maintain. I plan to write the server itself in Chicken scheme but I would need to maintain the existing code in C that opens and process those files.

Giving the size of the file, I want to share the memory space between C and Chicken and avoid copying values between areas. Is that even possible? Anyone has an idea on how can I address this?

Thanks in advance!

Pedro

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