Conjugate Gradient Solver for sparse symmetric matrices

Run CG (x86) using a sample problem from OpenFOAM:

make test_cg
./build/test_cg  

Run vectorized CG in Spyke RISC-V simulator:

make run_test_cg_vec

Supported matrix formats:

- [x] COO
- [x] CSR
- [x] ELL 
- [] SELL

Vectorized kernels (src/vectorized.c ):

• Matrix Vector product (ELL)
• Dot product
• SAXPY

conjugate_gradient/
├── include/        # Header files (.h)
│   ├── cg.h, coo.h, csr.h, ...
├── src/            # algorithm and matrix formats support (.c)
│   ├── cg.c, coo.c, csr.c, ...
├── tests/          
│   ├── tests_cg.c, test_matrix.c, ...  # tests (.c)
├── build/          # Executables 
├── data/           # OpenFoam i/o files
├── riscv/          # Riscv simulated experimets (Spike)
├── Makefile        
└── README.md