[WIP] CSR/ CSC Elemwise

[ivirshup]

Very WIP draft PR for elemwise operations on CSR and CSC arrays.

Currently just implements broadcasting operations between compressed 2d arrays. Cases that would be covered by a full implementation:

• Unary broadcasting (e.g. -a)
• Binary broadcasting
  • compressed_2d + compressed_2d
  • compressed_2d + scalar
  • compressed_2d + dense_1d
  • compressed_2d + sparse_1d

---

A quick benchmark:

import sparse
from sparse._compressed import CSR, CSC

gcxs_a = sparse.random((10000, 20000), .01, format="gcxs")
gcxs_b = sparse.random((10000, 20000), .01, format="gcxs")

csr_a = CSR(gcxs_a)
csr_b = CSR(gcxs_b)

scipy_a = csr_a.to_scipy_sparse()
scipy_b = csr_b.to_scipy_sparse()

%timeit gcxs_a + gcxs_b
# 999 ms ± 10.2 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

%timeit csr_a + csr_b
# 32.2 ms ± 1.9 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)

%timeit scipy_a + scipy_b
# 27.5 ms ± 894 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

Should provide some insight for #460

[hameerabbasi]

Thanks for this, @ivirshup. Let me know if you need any help or direction.

[codecov]

Codecov Report

Merging #465 (9b7f22c) into master (096f9b0) will decrease coverage by 1.24%.
The diff coverage is 64.42%.

@@            Coverage Diff             @@
##           master     #465      +/-   ##
==========================================
- Coverage   92.15%   90.91%   -1.24%     
==========================================
  Files          20       21       +1     
  Lines        3313     3445     +132     
==========================================
+ Hits         3053     3132      +79     
- Misses        260      313      +53     

[github-advanced-security]

CodeQL found more than 10 potential problems in the proposed changes. Check the Files changed tab for more details.

[hameerabbasi]

@ivirshup Do you plan to continue this?

[ivirshup]

I have some interest but probably not time. I would love for someone to take it over.

IIRC the biggest stumbling block was dispatch. If that could get worked out by someone else, I'd be interested in collaborating.