<!--
{
  "availability" : [
    "iOS: -",
    "iPadOS: -",
    "macCatalyst: -",
    "macOS: -",
    "tvOS: -",
    "visionOS: -",
    "watchOS: -"
  ],
  "documentType" : "symbol",
  "framework" : "Accelerate",
  "identifier" : "/documentation/Accelerate/SparseGMRESOptions",
  "metadataVersion" : "0.1.0",
  "role" : "Structure",
  "symbol" : {
    "kind" : "Structure",
    "modules" : [
      "Accelerate"
    ],
    "preciseIdentifier" : "c:@SA@SparseGMRESOptions"
  },
  "title" : "SparseGMRESOptions"
}
-->

# SparseGMRESOptions

Options for creating a generalized minimal residual (GMRES) method.

```
struct SparseGMRESOptions
```

## Overview

Use GMRES to solve *Ax = b* when *A* is symmetric indefinite or unsymmetric.

For symmetric positive-definite systems, use [`SparseConjugateGradient(_:)`](/documentation/Accelerate/SparseConjugateGradient(_:)). For rectangular or singular systems, use [`SparseLSMR(_:)`](/documentation/Accelerate/SparseLSMR(_:)).

## Topics

### Initializers

[`init()`](/documentation/Accelerate/SparseGMRESOptions/init())

[`init(reportError:variant:nvec:maxIterations:atol:rtol:reportStatus:)`](/documentation/Accelerate/SparseGMRESOptions/init(reportError:variant:nvec:maxIterations:atol:rtol:reportStatus:))

Returns a new GMRES options structure using the specified parameters.

### Inspecting GMRES Options

[`atol`](/documentation/Accelerate/SparseGMRESOptions/atol)

The absolute convergence tolerance.

[`maxIterations`](/documentation/Accelerate/SparseGMRESOptions/maxIterations)

The maximum number of iterations to perform.

[`nvec`](/documentation/Accelerate/SparseGMRESOptions/nvec)

The number of orthogonal vectors the operation maintains.

[`reportError`](/documentation/Accelerate/SparseGMRESOptions/reportError)

An optional error-reporting routine.

[`reportStatus`](/documentation/Accelerate/SparseGMRESOptions/reportStatus)

The function to report status.

[`rtol`](/documentation/Accelerate/SparseGMRESOptions/rtol)

The relative convergence tolerance.

[`variant`](/documentation/Accelerate/SparseGMRESOptions/variant)

The exact variant of GMRES to implement.

[`SparseGMRESVariant_t`](/documentation/Accelerate/SparseGMRESVariant_t)

Defines the exact variant of GMRES to implement


---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)