syevj

hipSOLVER Symmetric Eigenvalue via Generalized Jacobi Example

Description

This example illustrates how to compute the eigenvalues $W$ and eigenvectors $V$ from a symmetric $n \times n$ real matrix $A$ using the Jacobi method. For computing eigenvalues and eigenvectors of Hermitian (complex) matrices, refer to hipsolver[CZ]heevj.

Matrix $A$ is symmetric if $a_{ij} = a_{ji}$. The results are the eigenvalues $W$ and orthonormal eigenvectors $V$, meaning that the eigenvectors are orthogonal to each other and are normalized.

The results are verified by filling in the equation we wanted to solve: $A \underset{\text{right}}{\times} V = V \times W$ and checking the error.

Command line interface

The application has an optional argument:

• -n <n> with size of the $n \times n$ matrix $A$. The default value is 3.

Application flow

1. Parse command line arguments for dimensions of the input matrix.
2. Declare the host side inputs and outputs.
3. Initialize a random symmetric $n \times n$ input matrix.
4. Set the solver parameters.
5. Allocate device memory and copy input matrix from host to device.
6. Initialize hipSOLVER.
7. Query the required working space and allocate this on device.
8. Compute the eigenvector and eigenvalues.
9. Retrieve the results by copying from device to host.
10. Print the results
11. Validate the results
12. Free the memory allocations on device.

Key APIs and Concepts

hipSOLVER

• hipSOLVER (hipsolverHandle_t) gets initialized by hipsolverCreate and destroyed by hipsolverDestroy.
• hipsolverEigMode_t: specifies whether only the eigenvalues or also the eigenvectors should be computed. Passed to hipsolverDsyevj as jobz.
  • HIPSOLVER_EIG_MODE_VECTOR: compute the eigenvalues and eigenvectors.
  • HIPSOLVER_EIG_MODE_NOVECTOR: only compute the eigenvalues.
• hipsolverFillMode_t: specifies which part of $A$ to use.
  • HIPSOLVER_FILL_MODE_LOWER: data is stored in the lower triangle of $A$ .
  • HIPSOLVER_FILL_MODE_UPPER: data is stored in the upper triangle of $A$ .
• hipsolverCreateSyevjInfo: initializes a structure for the parameters and results for calling syevj.
• hipsolverDestroySyevjInfo: destroys the structure for the parameters and results for calling syevj.
• hipsolverXsyevjSetMaxSweeps: configures the max amounts of sweeps
• hipsolverXsyevjSetTolerance: configures the tolerance of syevj.
• hipsolverXsyevjSetSortEig : configures whether to sort the results or not
• hipsolver[SD]sygvj_bufferSize computes the required buffersize lwork from a given configuration.
• hipsolver[SD]syevj computes the eigenvalue and optional eigenvector.

  • There are 2 different function signatures depending on the type of the input matrix:

    • S single-precision real (float)
    • D double-precision real (double)

    For single- and double-precision complex values, the function hipsolver[CZ]heevj(...) is available in hipSOLVER.

    For example, hipsolverDsyevj(...) works on doubles. For the complex datatypes see hipsolver[CZ]heevj.

  • hipsolverHandle_t handle: hipSOLVER handle, see hipsolverCreate

  • hipsolverEigMode_t jobz: eigenvector output mode, see hipsolverEigMode_t.

  • hipsolverFillMode_t uplo: fill mode of $A$, see hipsolverFillMode_t.

  • int n: number of columns of $A$.

  • double* A: pointer to the input matrix $A$ on device memory.

  • int lda: leading dimension of $A$.

  • double* W: pointer to the output $W$ for the eigenvalues.

  • double* work: pointer to the working space.

  • int lwork: size of the working space.

  • int* info: pointer to write the convergence result to.

  • syevjInfo_t params: the structure for the parameters and results for syevj.

• hipsolverXsyevjGetSweeps: gets the amount of executed sweeps of syevj.
• hipsolverXsyevjGetResidual: gets the residual of syevj.

Used API surface

hipSOLVER

• hipsolverCreate
• hipsolverDestroy
• hipsolverCreateSyevjInfo
• hipsolverDestroySyevjInfo
• hipsolverDsyevj
• hipsolverDsyevj_bufferSize
• hipsolverXsyevjGetResidual
• hipsolverXsyevjGetSweeps
• hipsolverXsyevjSetMaxSweeps
• hipsolverXsyevjSetSortEig
• hipsolverXsyevjSetTolerance
• hipsolverEigMode_t
• hipsolverFillMode_t
• hipsolverHandle_t
• hipsolverSyevjInfo_t
• HIPSOLVER_EIG_MODE_VECTOR
• HIPSOLVER_FILL_MODE_LOWER

HIP runtime

• hipFree
• hipMalloc
• hipMemcpy
• hipMemcpyDeviceToHost
• hipMemcpyHostToDevice