Objects in PowerGrid

Object Reference

Transform objects

These objects implement forward and adjoint transforms. All can be used via the syntax below. The forward operations and adjoint operations are implemented via operator overloading in C++.

arma::Col<complex<double>> data;

//G is a transform object

ForwardTransform = G * data;
AdjointTransform = G / data;

Gfft

Implements the FFT (Fast Fourier Transform) sampled uniformly on the grid in both dimensions. This transform supports both GPU and CPU computation, relying on cufft for GPU computation and FFTW for GPU computation.

Gfft(nx, ny, nz)

Gdft

Implements a field corrected discrete Fourier transform (DFT). This object supports both CPU and GPU computation, although the CPU implementation not recommended for production work. The CPU version is not multithreaded and is O(n^2) in complexity, scaling very poorly.

Gdft(sizeKspace, sizeImg, kx, ky, kz, ix, iy, iz, FieldMap, timeVec)

Gnufft

Implements a non-Uniform Fast Fourier Transform (NUFFT). Field correction can be achieved with this object by combining with the TimeSegmentation object. This transform runs on both CPU and GPU, achieving good performance on both.

Gnufft(dataLength, gridOS, nx, ny, nz, k1, k2, k3, i1, i2, i3)

Model objects

These objects allow to perform different types of image reconstructions. Forward and adjoint operations are also defined via operator overloading in C++.

TimeSegmentation

Implements corrections for image distortions due to magnetic field susceptibility using a time segmentation approach. Hanning interpolator and min-max formulation are implemented.

TimeSegmentation(G, FieldMap, timeVec, dataLength, sizeImg, L, interpType, shots)

SENSE

Implements a sensitivity encoding (SENSE) operator.

SENSE( G, SENSEmap, dataLength, sizeImg, nc)

pcSENSE

Implements SENSE operator with phase correction for motion induced phase errors in DTI.

pcSENSE( kx, ky, kz, nx, ny, nz, nc, timeVec, SENSEmap, FieldMap, ShotPhaseMap)

mpipcSENSE

Implements the same operator than pcSENSE with MPI.

mpipcSENSE(kx, ky, kz, nx, ny, nz, nc, timeVec, SENSEmap, FieldMap, ShotPhaseMap, en, wor)

Same variables as pcSENSE. Two additional variables en , wor are boost::mpi variables for the MPI environment and MPI world communicator.

Penalty objects

These objects correspond to different penalty functions that can be used in the solver.

Robject

TVPenalty

Implements a total variation penalty. It inherits from the Robject.

TVPenalty(nx, ny, nz, beta, delta)

QuadPenalty

Implements a quadratic penalty. It inherits from the Robject class.

QuadPenalty(nx, ny, nz, beta);