gnss-sdr/src/algorithms/libs/fft_internal.h

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// File:       fft_internal.h
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#ifndef __CLFFT_INTERNAL_H
#define __CLFFT_INTERNAL_H

#include "clFFT.h"
#include <iostream>
#include <string>
#include <sstream>

using namespace std;

typedef enum kernel_dir_t
{
	cl_fft_kernel_x,
	cl_fft_kernel_y,
	cl_fft_kernel_z
}cl_fft_kernel_dir;

typedef struct kernel_info_t
{
	cl_kernel kernel;
	char *kernel_name;
	unsigned lmem_size;
	unsigned num_workgroups;
    unsigned num_xforms_per_workgroup;
	unsigned num_workitems_per_workgroup;
	cl_fft_kernel_dir dir;
	int in_place_possible;
	kernel_info_t *next;
}cl_fft_kernel_info;

typedef struct 
{
	// context in which fft resources are created and kernels are executed
	cl_context              context;
	
	// size of signal
	clFFT_Dim3              n;
	
	// dimension of transform ... must be either 1D, 2D or 3D
	clFFT_Dimension			dim;
	
	// data format ... must be either interleaved or plannar
	clFFT_DataFormat		format;
	
	// string containing kernel source. Generated at runtime based on
	// n, dim, format and other parameters
	string                  *kernel_string;
	
	// CL program containing source and kernel this particular 
	// n, dim, data format
	cl_program				program;
	
	// linked list of kernels which needs to be executed for this fft
	cl_fft_kernel_info		*kernel_info;
	
	// number of kernels
	int                     num_kernels;
	
	// twist kernel for virtualizing fft of very large sizes that do not
	// fit in GPU global memory
	cl_kernel				twist_kernel;
	
	// flag indicating if temporary intermediate buffer is needed or not.
	// this depends on fft kernels being executed and if transform is 
	// in-place or out-of-place. e.g. Local memory fft (say 1D 1024 ... 
	// one that does not require global transpose do not need temporary buffer)
	// 2D 1024x1024 out-of-place fft however do require intermediate buffer.
	// If temp buffer is needed, its allocation is lazy i.e. its not allocated
	// until its needed
	cl_int                  temp_buffer_needed;
	
	// Batch size is runtime parameter and size of temporary buffer (if needed)
	// depends on batch size. Allocation of temporary buffer is lazy i.e. its
	// only created when needed. Once its created at first call of clFFT_Executexxx
	// it is not allocated next time if next time clFFT_Executexxx is called with 
	// batch size different than the first call. last_batch_size caches the last
	// batch size with which this plan is used so that we dont keep allocating/deallocating
	// temp buffer if same batch size is used again and again.
	unsigned                  last_batch_size;
	
	// temporary buffer for interleaved plan
	cl_mem   				tempmemobj;
	
	// temporary buffer for planner plan. Only one of tempmemobj or 
	// (tempmemobj_real, tempmemobj_imag) pair is valid (allocated) depending 
	// data format of plan (plannar or interleaved)
	cl_mem                  tempmemobj_real, tempmemobj_imag;
	
	// Maximum size of signal for which local memory transposed based
	// fft is sufficient i.e. no global mem transpose (communication)
	// is needed
	unsigned					max_localmem_fft_size;
	
	// Maximum work items per work group allowed. This, along with max_radix below controls 
	// maximum local memory being used by fft kernels of this plan. Set to 256 by default
	unsigned                  max_work_item_per_workgroup;
	
	// Maximum base radix for local memory fft ... this controls the maximum register 
	// space used by work items. Currently defaults to 16
	unsigned                  max_radix;
	
	// Device depended parameter that tells how many work-items need to be read consecutive
	// values to make sure global memory access by work-items of a work-group result in 
	// coalesced memory access to utilize full bandwidth e.g. on NVidia tesla, this is 16
	unsigned                  min_mem_coalesce_width;
	
	// Number of local memory banks. This is used to geneate kernel with local memory 
	// transposes with appropriate padding to avoid bank conflicts to local memory
	// e.g. on NVidia it is 16.
	unsigned                  num_local_mem_banks;
}cl_fft_plan;

void FFT1D(cl_fft_plan *plan, cl_fft_kernel_dir dir);

#endif