Re: align dynamic array (for avx friendliness) hints? / possible??
On Tuesday, 3 August 2021 at 17:57:47 UTC, Ali Çehreli wrote: On 8/3/21 10:50 AM, james.p.leblanc wrote: > **Is there some highly visible place this is already documented? For what it's worth, it appears as "slice from pointer" in my index: http://ddili.org/ders/d.en/pointers.html#ix_pointers.slice%20from%20pointer Admittedly, one needs to know the concept first to think about that entry. :/ Ali Ali, Thanks for your message! (And even a bigger thanks for writing your book!) Your book was one of the first D programming books I read, and learned much from it. At the time of my reading, I was too much of a new-comer to the D-language to see the importance of the "slice from pointer". This concept is a hidden gem of the language IMHO! But, with my recent needs to mix and match native D with the FFTW C-functions in an avx friendly alignment, I was really searching for a way to keep the "best of both worlds". The "slice from pointer" concepts is a valuable one. I need to go back and read that section of book now! Best Regards, James
Re: align dynamic array (for avx friendliness) hints? / possible??
On 8/3/21 10:50 AM, james.p.leblanc wrote: > **Is there some highly visible place this is already documented? For what it's worth, it appears as "slice from pointer" in my index: http://ddili.org/ders/d.en/pointers.html#ix_pointers.slice%20from%20pointer Admittedly, one needs to know the concept first to think about that entry. :/ Ali
Re: align dynamic array (for avx friendliness) hints? / possible??
On Tuesday, 3 August 2021 at 16:32:34 UTC, kinke wrote: On Tuesday, 3 August 2021 at 12:33:56 UTC, james.p.leblanc wrote: Concise question: = I would like to use dynamic arrays, not for their dynamic sizing properties per se' (slicing, appending, etc). But, more for their memory protection and efficiencies (for example,using foreach). However, I must have the start of my array at an avx friendly 32 byte alignment. Is this easily acheivable? Background: === I am interfacing with fftw. If I use the fftw_malloc, then I am forced to either: 1) copy to/from the allocated arrays to/from my "standard" dlang dynamic arrays (loss of efficiency). or ... 2) use standard array/pointer mechanisms everywhere(loss of memory safely). My thinking is that I could forego the use of the fftw_malloc, and simply hand fftw functions my (properly aligned) pointer of my dlang dynamic array. All thoughts, comments, hints, greatly appreciated! James AFAIK, the GC only guarantees an alignment of 16. But you can turn any memory allocation into a slice, simply via ``` size_t length = ...; T* myPtr = cast(T*) fftw_malloc(length * T.sizeof); // or aligned_alloc, posix_memalign etc. T[] mySlice = myPtr[0 .. length]; foreach (ref e; mySlice) ... // free! ``` Dear Kinke, THANKS IMMENSELY! - This is exactly the kind of solution that I was hoping would be possible (elegant, simply, and clear). This really is the perfect solution, and opens up many possibilities for me. (Perhaps I had been using the wrong search terms, or perhaps everyone already knows how to use this "conversion of C arrays/pointers to D slices" solution... but I was stumped!) Again, thanks kindly **Is there some highly visible place this is already documented? If not, it would make a great blog post as it would be beneficial to any D newcomers bridging C/D and needing AVX alignments, etc.** Best Regards, James
Re: align dynamic array (for avx friendliness) hints? / possible??
On Tuesday, 3 August 2021 at 12:33:56 UTC, james.p.leblanc wrote: Concise question: = I would like to use dynamic arrays, not for their dynamic sizing properties per se' (slicing, appending, etc). But, more for their memory protection and efficiencies (for example,using foreach). However, I must have the start of my array at an avx friendly 32 byte alignment. Is this easily acheivable? Background: === I am interfacing with fftw. If I use the fftw_malloc, then I am forced to either: 1) copy to/from the allocated arrays to/from my "standard" dlang dynamic arrays (loss of efficiency). or ... 2) use standard array/pointer mechanisms everywhere(loss of memory safely). My thinking is that I could forego the use of the fftw_malloc, and simply hand fftw functions my (properly aligned) pointer of my dlang dynamic array. All thoughts, comments, hints, greatly appreciated! James AFAIK, the GC only guarantees an alignment of 16. But you can turn any memory allocation into a slice, simply via ``` size_t length = ...; T* myPtr = cast(T*) fftw_malloc(length * T.sizeof); // or aligned_alloc, posix_memalign etc. T[] mySlice = myPtr[0 .. length]; foreach (ref e; mySlice) ... // free! ```
align dynamic array (for avx friendliness) hints? / possible??
Concise question: = I would like to use dynamic arrays, not for their dynamic sizing properties per se' (slicing, appending, etc). But, more for their memory protection and efficiencies (for example,using foreach). However, I must have the start of my array at an avx friendly 32 byte alignment. Is this easily acheivable? Background: === I am interfacing with fftw. If I use the fftw_malloc, then I am forced to either: 1) copy to/from the allocated arrays to/from my "standard" dlang dynamic arrays (loss of efficiency). or ... 2) use standard array/pointer mechanisms everywhere(loss of memory safely). My thinking is that I could forego the use of the fftw_malloc, and simply hand fftw functions my (properly aligned) pointer of my dlang dynamic array. All thoughts, comments, hints, greatly appreciated! James
