feat: add sparse matrix toolchain - generator, parser, vec library

[HamzaMateen]

New features

Add three new tools under tools/src and tools/include:

• vec.h/vec.c: pure C11 growable array, replaces c-vector which required C23/gnu23
• genmat.h/genmat.c: sparse CSR matrix generator, generates directly in memory, no file I/O
• mtx_to_csr_formatter.h/.c: Matrix Market parser, COO intermediate, handles symmetric expansion

Reasons for changes/updates

• c-vector used typeof (magic macro) which is not valid C11, broke builds under -std=c11
• Initial implementation of parser built row_ptr on the fly assuming sorted row order, which the MM spec does not guarantee.
• Generator previously only wrote Matrix Market files, now produces CSR directly for use in pipeline without file IO round-trip

Fixes

Parser fix: read all entries into flat COO arrays first (order-independent), then build row_ptr via prefix sum over per-row counts, then scatter into CSR.

Symmetric expansion: O(nnz) mirror pass, not O(L^2).

Tested

• ash85.mtx: 85x85, 523 nnz after symmetric expansion
• SpGEMM A×B produces 1836 nnz, diagonal values match vertex degrees (correctness signal)
• Generator: 85x85 at density=0.05, 343 nnz, fed directly into SpGEMM

[Talha-Ahmed-1]

@HamzaMateen could you update it by saving the matrix to a file? It would help in input matrix analysis.

[HamzaMateen]

I will do so, thanks for the review.
One thing: should I save it in Dense format, Matrix Market, or CSR?

[Talha-Ahmed-1]

.mtx would be fine

I will do so, thanks for the review. One thing: should I save it in Dense format, Matrix Market, or CSR?