petsc-3.7.3 2016-07-24
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# VecScatterInitializeForGPU

Initializes a generalized scatter from one vector to another for GPU based computation.

### Synopsis

    #include "petscvec.h"
    PETSC_EXTERN PetscErrorCode VecScatterInitializeForGPU(VecScatter inctx,Vec x,ScatterMode mode)

### Input Parameters

| inctx | - scatter context generated by VecScatterCreate()
| x | - the vector from which we scatter
| mode | - the scattering mode, usually SCATTER_FORWARD. The available modes are: SCATTER_FORWARD or SCATTER_REVERSE

### Notes

Effectively, this function creates all the necessary indexing buffers and work vectors needed to move data only those data points in a vector which need to be communicated across ranks. This is done at the first time this function is called. Currently, this only used in the context of the parallel SpMV call in MatMult_MPIAIJCUSP or MatMult_MPIAIJCUSPARSE.

This function is executed before the call to MatMult. This enables the memory transfers to be overlapped with the MatMult SpMV kernel call.

### See Also

VecScatterFinalizeForGPU(), VecScatterCreate(), VecScatterEnd()

Level:intermediate
Location: src/vec/vec/utils/vscat.c
Index of all Vec routines
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Index of all manual pages