Houffaneh Osman
halio029@uottawa.ca
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Single Instruction, Multiple Data
Part of Flynn Taxonomy computer
classification
Multiple processors
◦ Different data streams
 Same instruction executed
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Able to operates on multiple data items at the
same time
Computation : The most minimal time
possible
◦ Vectors
◦ Matrices
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Better speedup then sequential
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Two type of processors
◦ True SIMD
◦ Pipelined SIMD
 Divide a instruction into smaller function
 Execute smaller function in parallel on different data
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Single control unit
M processing elements act as arithmetic unit
N data elements (or even more then M)
Processor elements receives instruction from
control unit
If a processor element need information from
another processor element
◦ Send request to control unit and it manage the
memory exchanges
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Single control unit
M processing elements act as arithmetic unit
N data elements (or even more then M)
Processor elements receives instruction from
control unit
Processing elements able to share their
memory without control unit access
True SIMD : Distributed Memory
True SIMD : Shared Memory
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Cell used : IBM Cell BE
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The Cell Broadband Engine (CBE)
◦ Single-chip multiprocessor
 with 9 processor
◦ All processor share the same main storage
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Processor function used in 2 functions
◦ PowerPC Processor Element (PPE)
◦ Synergistic Processor Element (SPE)
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VMX : Vector Multimedia eXtension to the
PowerPC architecture
◦ Utilizes data parallelism for faster performance
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SIMD in VMX and SPE (Reference IBM Cell Programming)
◦ 128bit-wide datapath
◦ 128bit-wide registers
◦ 4-wide fullwords, 8-wide halfwords, 16-wide bytes
◦ SPE includes support for 2-wide doublewords
Vector Programming
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Each of the 4 elements in VA and VB are
added and their sum placed in VC
VC = vec_add(VA,VB)
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SIMD Unprocessable Patterns
◦ Case where the instruction differ for each
processing element
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SIMD Processable Patterns
◦ Case where the instruction are the same for each
processing element
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Register view of the add instruction in previous slide
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VC = vec_add(VA,VB)
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Permute method or shuffling
◦ Between two vector
◦ Third vector used for control vector
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VT = vec_perm(VA,VB,VC)
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SSE : Streaming SIMD Extensions
◦ Instruction set to the x86 architectures
◦ Extension of 128-bit
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Introduced in 1999 in the Pentium III
◦ Latest version : SSE5 before revision
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Future extension from Intel
◦ AVX : Advanced Vector Extensions
◦ 256-bit instructions
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Image Processing
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Digital Signal Processing
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Encoding
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Streaming load
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Streaming load instruction
◦ Enables faster read
◦ Improves performance of application that ‘s using
the GPU and CPU
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SIMD improve encoding speed
◦ Required arithmetic performed on pixel
 Pixel in a video -> high level of parallelism required
Matrix multiplication – No data parallelism
Matrix multiplication – Employed data
parallelism
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Native vs Traditional programming
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Auto-vectorization
◦ Detection of low-level operation
◦ Convert these sequential program to process 2 to
up to 16 elements in one operation
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Auto-parallization
◦ Turning sequential code into multi-threaded
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Intel C++ Compiler
◦ Serial section of input program -> multithreaded
code
◦ Compiler also efficient in order to not have too
much overhead when creating multithreads
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Intel® Architecture Code Analyzer
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PGI CDK Cluster Development Kit
◦ AMD Opteron
◦ Intel Core 2
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GNU Compiler for C and C++
◦ Nested Loops conditions
◦ Multidimensional arrays
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PGI CDK Cluster Development Kit
◦ SSE vectorization
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Developed to utilized
◦ Multi-core processors
◦ Graphics processing units
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Takes advantages of the SIMD and core
processing elements
Portion of C/C++ code that have parallelism
can be used in conjunction with ArBB
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Isolated data objects from rest of codes
◦ Intel mention this imposes a restrictions
◦ Restrictions eliminates locks and data races
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Threading by itself
◦ Do not provide access to per-core vector
parallelism
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ArBB API provides programming models at
software level for developers
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IBM Corp and Sony Computer Entertainment, “Software Development Kit for Multicore
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L.Dong-hwan, S. Wonyong, ``Importance of SIMD computation reconsidered,''Parallel
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p
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http://www.wolfire.com/