2012/06/22
Email: nomura@am.ics.keio.ac.jp
Contents
GPU (Graphic Processing Unit)
 CUDA Programming
 Target: Clustering with Kmeans
 How to use toolkit1.0
 Towards the fastest program

GPU (Graphic Processing Unit)

GPU
SM
SM
Multicore processor
SM
…
 Several handreds cores
 SP: Core in GPU
Global Memory
 SM: Composed of SPs

High memory bandwidth
Table: Specification of GeForce280
SP
SP
30
(Each of them has 8 SP)
SP
SP
141.7 GB/s
SP
SP
SP
SP
SP
240
SM
Memory
Bandwidth
SM
SP: Streaming Processor
SM: Streaming MultiProcessor
Flow of CUDA Program
Allocate GPU memory
1.

Array
Host
cudaMalloc()
CPU
Transfer input data
2.

input 2
output 2
…
…
input N
output N
…
Global Memory
Data Transfer
SP
Data Transfer
cudaFree()
SP
Kernel

SP
Kernel
5.
Device (GPU)
Kernel
4.
output 1
cudaMemcpy()
Execute kernel
Transfer result data
Free GPU memory
3.
Main
Memory
input 1
Array
input 1
output 1
input 2
output 2
…
…
input N
output N
Target application：clustering
with Kmeans

A famous method for clustering
A program with kmeans method for a
host processor is given. Modify it so that
it works on GPU as fast as possible.
 GeForce Tesla (GTX280) in Amano Lab.
can be used for this contest.

Kmeans method(1/5)
Initial state：
STEP1:
Nodes in a certain color is distributed
Centre of gravity is computed for
randomly.
each colored node set.
(Here, 100nodes with 5 colors are
(X in the figure is each centre)
shown)
Reference URL:
http://d.hatena.ne.jp/nitoyon/20090409/kmeans_visualise
Kmeans method(2/5)
STEP2
The color of each node is
changed into that of the nearest
centre.
STEP1:
Again, the centre of gravity is
computer in node set with the
same color.
Kmeans method(3/5)
STEP2:
Again, the color of each node is
changed into that of the nearest
centre.
STEP1:
Again, the centre of gravity is
computer in node set with the
same color.
Kmeans method(4/5)
STEP2:
Again, the color of each node is
changed into that of the nearest
centre.
STEP1:
Again, the centre of gravity is
computer in node set with the
same color.
Kmeans method(5/5)
STEP2:
Again and again, the color of
each node is changed into that of
the nearest centre.
Terminate Condition：
The color of all nodes are the
same as the color of the centre,
thus, there is no need to change
the color.
→Terminate.
How to start

ssh 131.113.69.98 for login.
 Your account has been available. If you have not
received mail about account, please send mail to
nomura@am.ics.keio.ac.jp .
Download kmeans.tar.gz and ungip.
 There are useful sample codes in kmeans.
 Mission１：Make GPU version based on CPU
version.

 Describe gpuKMeans in kmeans.cu
cpuKMeans in main.cu is a CPU version for reference.

Mission２：Optimize the CPU code so that it
runs as fast as possible.
Toolkit1.0

kmeans.cu
 To describe K-means program for GPU
 Please modify this file

main.cu
 To read input data, describe CPU program
 Modification forbidden

check.c
 To visualize output data by OpenCV

gen.c
 To generate input data


Makefile
data/
 Input data

result/
 Output data
How to use Toolkit1.0

$ make
 Compile

$ make gpu
 Execute GPU Program

$ make cpu
 Execute CPU Program

$ ./gen SEED (SEED = 0,1,2,…)
 Generate input data
Sample Code

Vector addition program for GPU
 $ make : Compile
 $ ./main : Program run

Point
 Memory allocation on GPU
○ cudaMalloc(), cudaFree()
 Data transfer between CPU and GPU
○ cudaMemcpy()
 Format of GPU kernel function
Towards the fastest program

Minimum requirement
 Implementation K-means program on GPU
 Parallelizing STEP1 or STEP2 in K-means

How to optimize program
 Parallelizing both of STEP1 and STEP2
 Shared memory, Constant memory
 Coalesced Memory Access etc
 Web Site
 NVIDIA GPU Computing Document:
http://developer.nvidia.com/nvidia-gpu-computingdocumentation
 Fixstars CUDA Infromation Site:
http://gpu.fixstars.com/index.php/
Announcement:

If you have not an account mail to
nomura@am.ics.keio.ac.jp
 Your name should be included in the mail.
Deadline：7/22 (Fri) 24:00
 Copy follows in ~/comparch

 Source code and simple report
Please check the web site. Additional
information will be on it.
 If you have any question about the contest,
please send mail to:
nomura@am.ics.keio.ac.jp
