compute_backward<typename descriptor_type, typename data_type>
Computes the backward FFT. This routine belongs to the
oneapi::mkl::dft
namespace.Description
The
. This function throws an
compute_backward<typename descriptor_type, typename data_type>
function accepts a descriptor object followed by one or more data parameters. Given a successfully configured and committed descriptor, this function computes the backward FFT, that is, the transform with the plus sign in the exponent, 
std::runtime_exception
in the case that it fails.The FFT descriptor must be properly configured prior to the function call. Function calls needed to configure an FFT descriptor for a particular call to an FFT computation function are summarized in Configuring and Computing an FFT in C/C++.
The number of data parameters to be provided depends exclusively on the
descriptor’s PLACEMENT
configuration parameter. In-place (default) operations require only one data
parameter while out-of-place operations take two distinct data parameters. The
function’s behavior is undefined otherwise.
API
Syntax
Using SYCL buffers
namespace oneapi::mkl::dft{
void compute_backward<descriptor_type,
data_type>(descriptor_type &desc, cl::sycl::buffer<data_type,
1> &inout);
void compute_backward<descriptor_type, input_type,
output_type>(descriptor_type &desc,
cl::sycl::buffer<input_type, 1> &in,
cl::sycl::buffer<output_type, 1> &out);
}
Using USM pointers
namespace oneapi::mkl::dft{
cl::sycl::event compute_backward<descriptor_type,
data_type>(descriptor_type &desc, data_type* inout, const
std::vector<cl::sycl::event> &dependencies = {});
cl::sycl::event compute_backward<descriptor_type, input_type,
output_type>(descriptor_type &desc, input_type* in,
output_type* out, const
std::vector<cl::sycl::event> &dependencies = {});
}
Include Files
- oneapi/mkl/dfti.hpp
Input Parameters
Name | Supported types | Description |
---|---|---|
inout |
| Input/output data |
in |
| Input data |
- The parameter name inout (resp. in) corresponds to using a descriptor configured to operate INPLACE (resp. NOT_INPLACE). See descriptor’s PLACEMENT.
- Whether using i. SYCL buffers or ii. device-accessible USM pointers, the length of the containing array must be no less than specified at construction of the descriptor.
Output Parameters
Name | Supported types | Description |
---|---|---|
inout |
| Input/output data |
out |
| Output data |
- The parameter name inout (resp. out) corresponds to using a descriptor configured to operate INPLACE (resp. NOT_INPLACE). See descriptor’s PLACEMENT.
- Whether using i. SYCL buffers or ii. device-accessible USM pointers, the length of the containing array must be no less than specified at construction of the descriptor.
- In case of out-of-place operations, the same type is to be used for the parameters in and out.