1. Taxanomy of parallel machines

2. Taxonomy of parallel machines Memory – Shared mem. – Distributed mem. Control – SIMD – MIMD

3. Shared Memory Multiprocessor

4. Conventional Computer Consists of a processor executing a program stored in a (main) memory: Each main memory location located by its address. Addresses start at 0 and extend to 2 b - 1 when there are b bits (binary digits) in address. Main memory Processor Instructions (to processor) Data (to or from processor)

5. Shared Memory Multiprocessor System Natural way to extend single processor model - have multiple processors connected to multiple memory modules, such that each processor can access any memory module : Processors Interconnection network Memory module One address space

6. Simplistic view of a small shared memory multiprocessor Processors Shared memory Bus

7. Typical Shared Memory Multiprocessor Processor L2 Cache Bus interface L1 cache Processor L2 Cache Bus interface L1 cache Processor L2 Cache Bus interface L1 cache Processor L2 Cache Bus interface L1 cache Memory controller Memory I/O interface I/O bus Processor/ memory bus Shared memory

8. Programming Shared Memory Multiprocessors Threads - programmer decomposes program into individual parallel sequences, (threads), each being able to access variables declared outside threads. Example: Pthreads Sequential programming language with preprocessor compiler directives to declare shared variables and specify parallelism. Example: OpenMP or Cilk - needs OpenMP or Cilk compiler

9. Distributed Memory Multiprocessor

10. Computers connected through an interconnection network: Processor Interconnection network Local Computers Messages memory

11. Interconnection Networks Limited and exhaustive interconnections 2- and 3-dimensional meshes Hypercube (not now common) Using Switches: –Crossbar –Trees –Multistage interconnection networks

12. Two-dimensional array (mesh) Also three-dimensional - used in some large high performance systems. Links Computer/ processor

13. Three-dimensional hypercube

14. IBM Blue Gene

16. Tree Switch element Root Links Processors

17. Four-dimensional hypercube Hypercubes popular in 1980/90’s - not now

18. Multistage Interconnection Network Example: Omega network 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 Inputs Outputs 2´ 2 switch elements (straight-through or crossover connections)

19. Crossbar switch Switches Processors Memories

20. Message-Passing Distributed memory parallel machines are usually programmed via message passing. Industry standard: MPI Processor Interconnection network Shared Computers Messages memory

21. Flynn’s Classifications

29. Taxanomy of parallel machines Distributed memory Shared memory MIMDSIMD clusters multi-core CM/2 (legacy) GPU