4 ms·

jboy, Can nim-pymod be used as VLA's for nim? I'm not too fond of the nim seq'type (bit slow for my usage) and prefer arrays, but need their length allocated at

jboy, Can nim-pymod be used as VLA's for nim? I'm not too fond of the nim seq'type (bit slow for my usage) and prefer arrays, but need their length allocated at runtime. Can this be done via (albeit a clunky route) through nim-pymod? i.e arrays created and accessed all in nim (no python)?

jboy 11y ago
Hi, the short answer is "Yes, but ...". Yes, Pymod's PyArrayObject can be created & accessed entirely in Nim; yes, its length (actually, shape) is specified at runtime; and yes, it can be resized after creation. However, Pymod's PyArrayObject is designed for maximum binary compatibility with Numpy. As such: 1. It uses Numpy's array creation functions (such as `createSimpleNew`), which in turn uses the Python runtime memory allocator. So at the very least, Pymod assumes you've linked against `-lpythonX.Y`. 2. It integrates with Python's GC rather than Nim's GC. (This is why it's passed around as `ptr PyArrayObject` rather than `ref PyArrayObject` -- it's untouchable by the Nim GC, but instead uses Python refcounts.) Of course, we do intend to extend Pymod to include a pure-Nim sibling for PyArrayObject, but it doesn't exist yet. If you want a high-quality no-Python-dependency VLA in Nim right now, I'd recommend this library by Andrea Ferretti [ https://github.com/unicredit/linear-algebra https://github.com/unicredit/linear-algebra ]. It can link against your system BLAS, in addition to offering GPU support using NVIDIA CUDA. Andrea is another member of the Nim community who does a lot of scientific computing: http://rnduja.github.io/2015/10/21/scientific-nim/ http://rnduja.github.io/2015/10/21/scientific-nim/
- stevieboy 11y ago
  Ok, looking at the linear-algebra VLA stuff now. Thanks for the detailed reply and suggestion. (and apologies to original OP for veering off-topic... the new ndslice package looks like a pretty cool addition the D libraries, I'll be having a look at that too)

jboy 11y ago

Hi, the short answer is "Yes, but ...". Yes, Pymod's PyArrayObject can be created & accessed entirely in Nim; yes, its length (actually, shape) is specified at runtime; and yes, it can be resized after creation. However, Pymod's PyArrayObject is designed for maximum binary compatibility with Numpy. As such: 1. It uses Numpy's array creation functions (such as `createSimpleNew`), which in turn uses the Python runtime memory allocator. So at the very least, Pymod assumes you've linked against `-lpythonX.Y`. 2. It integrates with Python's GC rather than Nim's GC. (This is why it's passed around as `ptr PyArrayObject` rather than `ref PyArrayObject` -- it's untouchable by the Nim GC, but instead uses Python refcounts.) Of course, we do intend to extend Pymod to include a pure-Nim sibling for PyArrayObject, but it doesn't exist yet. If you want a high-quality no-Python-dependency VLA in Nim right now, I'd recommend this library by Andrea Ferretti [ https://github.com/unicredit/linear-algebra https://github.com/unicredit/linear-algebra ]. It can link against your system BLAS, in addition to offering GPU support using NVIDIA CUDA. Andrea is another member of the Nim community who does a lot of scientific computing: http://rnduja.github.io/2015/10/21/scientific-nim/ http://rnduja.github.io/2015/10/21/scientific-nim/

stevieboy 11y ago
Ok, looking at the linear-algebra VLA stuff now. Thanks for the detailed reply and suggestion. (and apologies to original OP for veering off-topic... the new ndslice package looks like a pretty cool addition the D libraries, I'll be having a look at that too)