---
title: rtol
framework: accelerate
role: symbol
role_heading: Instance Property
path: accelerate/sparsegmresoptions/rtol
---

# rtol

The relative convergence tolerance.

## Declaration

```swift
var rtol: Double
```

## Discussion

Discussion ‖ b-Ax ‖₂ < rtol * ‖ b-Ax₀ ‖₂ + atol indicates convergence. If rtol = 0, the operation uses the default value of sqrt(epsilon). If it’s negative, the system treats rtol as 0.0 (it doesn’t use the default).

## See Also

### Inspecting GMRES Options

- [atol](accelerate/sparsegmresoptions/atol.md)
- [maxIterations](accelerate/sparsegmresoptions/maxiterations.md)
- [nvec](accelerate/sparsegmresoptions/nvec.md)
- [reportError](accelerate/sparsegmresoptions/reporterror.md)
- [reportStatus](accelerate/sparsegmresoptions/reportstatus.md)
- [variant](accelerate/sparsegmresoptions/variant.md)
- [SparseGMRESVariant_t](accelerate/sparsegmresvariant_t.md)