Format Selection Guide

Choose the right sparse format for your use case.

Decision Tree

1. Building a Matrix?

• Use LIL or COO for construction
• Convert to CSR/CSC before computation

2. Row Operations?

• Use CSR for row slicing and matvec

3. Column Operations?

• Use CSC for column slicing

4. Banded Matrix?

• Use DIA for diagonal/banded structures

5. Solving Linear Systems?

• Use CSC for direct solvers
• Use CSR for iterative solvers

Quick Reference

Task	Recommended Format
Build incrementally	LIL, COO
Matrix-vector product	CSR
Row slicing	CSR
Column slicing	CSC
Direct solve (splu)	CSC
Iterative solve (cg)	CSR
Banded matrices	DIA
Format conversion	COO

Workflow

from scipy import sparse

def main():
    # 1. Build with LIL
    lil = sparse.lil_matrix((1000, 1000))
    # ... add entries ...

    # 2. Convert to CSR for computation
    csr = lil.tocsr()

    # 3. Use CSR for all operations
    # ... matrix operations ...

if __name__ == "__main__":
    main()