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# SparseConjugateGradient()

Returns a conjugate gradient (CG) method.

```
func SparseConjugateGradient() -> SparseIterativeMethod
```

## Return Value

A [`SparseIterativeMethod`](/documentation/Accelerate/SparseIterativeMethod) structure that represents a default conjugate gradient method.

## Discussion

Use CG to solve *Ax = b* when *A* is symmetric positive-definite. The method may break down or fail to converge if *A* isn’t positive-definite.

For square, full-rank, unsymmetric or indefinite equations, use [`SparseGMRES(_:)`](/documentation/Accelerate/SparseGMRES(_:)). For rectangular or singular systems, use [`SparseLSMR(_:)`](/documentation/Accelerate/SparseLSMR(_:)).

---

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