about 2D FFT

[Dawn_L_]

    Hi,

      Below is a block of codes for using 2D FFT from MKL:

         MKL_LONG      flen1[2]={nffty,nfftx};    
         MKL_LONG      status;
    
         DFTI_DESCRIPTOR_HANDLE      hand1;  
         status=DftiCreateDescriptor(&hand1,DFTI_SINGLE,DFTI_COMPLEX,2,flen1); 
         status=DftiCommitDescriptor(hand1);                 
         status=DftiComputeForward(hand1,tmp); 
         
         tmp is a 2D complex array.
         
         problems:
                               
         tmp in DftiComputeForward: if tmp is given by tmp[ ][ ] the compiling can go through and the block codes works well. If tmp is given by **tmp and alloc memory to it, the compiling can go through but executing is crushed at DftiComputeForward.
            
          So, the problem is in/out parameter in DftiComputeForward has to be hard-coding 2D array and cannot be pointer type?

        Any answer is welcomed. Thank you very much.

[Dmitry_B_Intel]

You are correct, the i/o pointers should point directly to the data, not to the pointers to the rows/columns. See also what FFTW3 documentation says on this.

Thanks
Dima

[Dawn_L_]

   Thank you, Dima, for your reply.

   Same block code with different problem as below:

   complex       tmp[nffty][nfftx],swap[nffty][nfftx];
    
    MKL_LONG      flen1[2]; 
    flen1[0]=nffty; 
    flen1[1]=nfftx; 
    
    MKL_LONG      status;
    
    DFTI_DESCRIPTOR_HANDLE      hand1;  
    status=DftiCreateDescriptor(&hand1,DFTI_SINGLE,DFTI_COMPLEX,2,flen1); 
    status=DftiCommitDescriptor(hand1);                    
    status=DftiComputeForward(hand1,tmp);     

   Problem: If I define nffty=1024 and nfftx=1024, the executing of program is crushed at  "complex   tmp[nffty][nfftx],swap[nffty][nfftx];"

   Do you think there is size limitation for 2D complex array of tmp and swap?

   Thank you very much in advanced.

[Evgueni_P_Intel]

Yes, 16 megabytes exceed the typical size of thread stack.

Try allocating the arrays at run time or extend the size of stack using an appropriate compiler switch.