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# PCGAMGSetAggressiveLevels

Use aggressive coarsening on first n levels

## Synopsis

    #include "petscpc.h"
    PetscErrorCode PCGAMGSetAggressiveLevels(PC pc, PetscInt n)

Logically Collective

## Input Parameters

- pc - the preconditioner context

- n - 0, 1 or more

## Options Database Key

- -pc_gamg_aggressive_coarsening <n,default = 1> - the flag

## Note

By default, aggressive coarsening squares the matrix (computes \( A^T A\)) before coarsening. Calling `PCGAMGSetAggressiveSquareGraph()` with a value of `PETSC_FALSE` changes the aggressive coarsening strategy to use MIS-k, see `PCGAMGMISkSetAggressive()`.

## See Also

the Users Manual section on PCGAMG, the Users Manual section on PCMG, KSP: Linear System Solvers, `PCGAMG`, `PCGAMGSetThreshold()`, `PCGAMGMISkSetAggressive()`, `PCGAMGSetAggressiveSquareGraph()`, `PCGAMGMISkSetMinDegreeOrdering()`, `PCGAMGSetLowMemoryFilter()`

## Level

intermediate

## Location

src/ksp/pc/impls/gamg/agg.c

## Implementations

PCGAMGSetAggressiveLevels_AGG() in src/ksp/pc/impls/gamg/agg.c

Index of all PC routines
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Index of all manual pages