The VAMPIR and PARAVER performance analysis tools applied to a wet chemical etching parallel algorithm - PowerPoint PPT Presentation

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The VAMPIR and PARAVER performance analysis tools applied to a wet chemical etching parallel algorithm

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S. Boeriu1 and J.C. Bruch, Jr.2. 1Center for Computational Science and Engineering ... This material is based upon work supported by the National Science Foundation ... – PowerPoint PPT presentation

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Title: The VAMPIR and PARAVER performance analysis tools applied to a wet chemical etching parallel algorithm


1
The VAMPIR and PARAVER performance analysis tools
applied to a wet chemical etching parallel
algorithm
  • S. Boeriu1 and J.C. Bruch, Jr.2
  • 1Center for Computational Science and Engineering
  • 2Department of Mechanical and Environmental
    Engineering
  • and Department of Mathematics
  • University of California, Santa Barbara
  • http//www.engineering.ucsb.edu/hpscicom

2
Acknowledgements
This material is based upon work supported by the
National Science Foundation under Grant 0086262.
This research was conducted using the resources
of the San Diego Supercomputer Center. http//www.
npaci.edu/Horizon/guide_linked/bh_tools_txt.html

3
Outline of Presentation
  • Introduction (Physical problem)
  • Problem formulation
  • Fixed domain formulation
  • Numerical algorithm
  • Test case
  • Performance tools and considerations

  • a. VAMPIR
  • b. PARAVER
  • Diagnostic example
  • Conclusions

4
Physical problem
A gap of width 2a and length L is to be
etched in a flat plate. The remainder of
the plate is covered with a protective
(photoresist) layer. Since it is assumed that L
gtgt2a, the problem can be considered as
two-dimensional.
Figure 1. Physical problem
5
Simplifying assumptions
  1. There is no convection in the etching medium
  2. The etching process is isotropic
  3. The thickness of the photoresist layer is
    infinitely small
  4. Only one component of the etching liquid
    determines the process

6
Problem formulation
Mathematical model The etching fluid W(t) is
bounded by the outer boundary G1 the
photoresist layer G2(t) and the moving boundary
S(t). D\ W(t) denotes part of the solid.
Figure 2. Side view of physical problem
showing mathematical problem setup.
7
Fixed domain formulation
Figure 3. Fixed domain
mathematical formulation.
8
Numerical Algorithm
The basic numerical algorithm is
with
in
and
9
Numerical algorithm (cont.)
with
in
(the rectangular region of the plates cross
section)
10
Test case
Maxrow1 ( of rows in the top
region) 280 Maxcol1 (
of columns in the top region) 321
Maxrow2 ( of rows in the bottom region)
80 Maxcol2 ( of columns in
the bottom region) 161 Maxtime (
of time steps) 5
Dt (size of time steps)
1 q
(successive over-relaxation factor)
1.935 B (non-dimensional number)
10.0
11
Domain decomposition
Figure 5. Domain decomposition of mathematical
problem into sixteen subregions showing the flow
of computations.
12
Load balancing information for the test case
Processors 2 4 8 16 32 64
Bottom Processors 1 1 1 2 4 8
Bottom Points 12888 12888 12888 6440 3220 1610
Top Processors 1 3 7 14 28 56
Top Points 89880 30174 12840 6420 3210 1605
Diff Points 77000 17294 40 20 10 5
13
Figure 4. Ideal versus
obtained speedup
14
Figure 6. Moving boundaries
at various times.
15
Performance tools and considerations
  • The parallel program is monitored while
  • it is executed. Monitoring produces
  • performance data that is interpreted in
  • order to reveal areas of poor performance.
  • The program is then altered and the
  • process is repeated until an acceptable
  • level of performance is reached.

16
VAMPIR (Visualization and Analysis of MPI
Resources 2.0)
  • VAMPIR 2.0 is a post-mortem trace visualization
    tool from Pallas GmbH
  • http//www.pallas.com
  • It uses the profile extensions to MPI
    and
  • permits analysis of the message events where
  • data is transmitted between processors during
  • execution of a parallel program. It has a
  • convenient user-interface and an excellent
  • zooming and filtering. Global displays show
    all
  • selected processes.

17
  • Global Timeline detailed application execution
    over time axis
  • Activity Chart presents per-process profiling
    information
  • Summaric Chart aggregated profiling information
  • Communication Statistics message statistics for
    each process pair
  • Global Communication Statistics collective
    operations statistics
  • I/O Statistics MPI I/O operation statistics
  • Calling Tree global dynamic calling tree

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PARAVER(Parallel Program Visualization and
Analysis Tool)
  • PARAVER is a flexible parallel program
    visualization and analysis tool based on an
    easy-to-use Motif GUI (graphical user interface)
  • PARAVER was developed to respond to
    the
  • basic need to have a qualitative perception of
    the
  • application behavior by visual inspection and
    then
  • to be able to focus on the detailed
    quantitative
  • analysis of the problems.


28
Paraver (Parallel Program Visualization and
Analysis Tool)
  • Powerful flexible parallel program visualization
    tool based on an easy-to-use Motif GUI (graphical
    user interface)
  • Developed by
  • European Center for Parallelism of
    Barcelona (CEPBA)
  • Universitat Politecnica de Catalunya
  • http//www.cepba.upc.es/


29
  • Paraver is designed to visualize and analyze
  • - Communication and load balance
  • - Combining OpenMP and MPI
  • - Hardware performance and counters
  • Usage
  • - Compile programs with special
    libraries
  • - Run programs to produce trace files
  • - View and analyze traces
  • - Designed to help in program
    understanding and optimization

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Inefficient programming example
  • Load imbalance (inefficient memory use)
  • Cache misses and page faults
  • Stride minimization (efficient memory use)

39
Load imbalance - VAMPIR
Figure 7. Load imbalance in the plate region.
40
Load imbalance - PARAVER
Figure 8. Load imbalance in the plate region.
41
The memory hierarchy
42
Array Allocation
43
Example of coding
  • c-
  • c- calculate error in the top region and update
    u1old
  • do 370 i iamnumrows1 1,lastrow
  • do 380 j 2,maxcol1
  • if (abs(u1new(i,j) -
    u1old(i,j)).gt.err)
    then
  • err abs(u1new(i,j) - u1old(i,j))
  • endif
  • u1old(i,j) u1new(i,j)
  • 380 continue
  • 370 continue
  • c-

c- do 380 j 2,maxcol1 do 370 i
iamnumrows1 1,lastrow if (
abs(u1new(i,j) - u1old(i,j)) .gt. err) then
err abs(u1new(i,j) - u1old(i,j))
endif u1old(i,j)
u1new(i,j) 370 continue 380 continue c-

Figure 9. A piece of the etching code
(non-optimized on the left and optimized on the
right).
44
Load balance - VAMPIR
Figure 10. Approximate load balance.
45
Load balance - PARAVER
Figure 11. Approximate load balance.
46
Conclusions
  • A significant factor that affects the
    performance of a parallel application is the
    balance between communication and workload. The
    challenge of the message passing model is in
    reducing message traffic over the interconnection
    network. To fully understand the
  • performance behavior of such applications,
    analysis and
  • visualization tools are needed. Two such
    tools, VAMPIR
  • and PARAVER, were used to analyze the
    performance of
  • the etching application. It was seen that
    optimization of
  • the parallel code can be carried out in an
    iterative process
  • involving these tools to investigate
    performance issues.

47
Web Sites
  • Project site
  • http//www.engineering.ucsb.edu/hpscicom
  • San Diego Supercomputer Center
  • http//www.npaci.edu/Horizon/guide_linked/bh_tools
    _txt.html
  • VAMPIR
  • http//www.pallas.com
  • PARAVER
  • http//www.cepba.upc.es/
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