1. FFTW and Matlab*p
Richard Hu
6.338 Project

2. Outline
Background
Work Done and Algorithm
Results
Q&A

3. Background
Integrating FFTW into Matlab*p requires translating from block-cyclic distribution to row distribution and back
Want to minimize communication and delays

4. Work Done
Program translates between virtually any block-cyclic distribution and any row distribution
Requires knowledge of positions of blocks and rows for other processors

5. Algorithm
Clump blocks in the same row together to achieve “temporary” row distribution
Shift rows between processors to achieve “desired” row distribution
Calculate Fourier Transform
Shift rows between processors back to “temporary” row distribution
Divide rows into blocks

6. Algorithm
Gather positions of blocks and rows for other processors and group into sorted arrays
Iterates through every position in the matrix and determines the sending and receiving processor

7. Results

8. Variants One processor acts as head node, directing sends and receives
Each node keeps track of the rows and columns it should send/receive and all communication is done at the end.

9. Questions