Modelica Performance Analyzer

A common problem when simulating models in an equation-based language like Modelica is that the model may contain non-linear equation systems. These are solved in each time-step by extrapolating an initial guess and running a non-linear system solver. If the simulation takes too long to simulate, it is useful to run the performance analysis tool. The tool has around 5~25% overhead, which is very low compared to instruction-level profilers (30x-100x overhead). Due to being based on a single simulation run, the report may contain spikes in the charts.

When running a simulation for performance analysis, execution times of user-defined functions as well as linear, non-linear and mixed equation systems are recorded.

To start a simulation in this mode, turn on profiling with the following command line flag >>> setCommandLineOptions("--profiling=all")

The generated report is in HTML format (with images in the SVG format), stored in a file modelname_prof.html, but the XML database and measured times that generated the report and graphs are also available if you want to customize the report for comparison with other tools.

Below we use the performance profiler on the simple model A:

model ProfilingTest
  function f
    input Real r;
    output Real o = sin(r);
  end f;
  String s = "abc";
  Real x = f(x) "This is x";
  Real y(start=1);
  Real z1 = cos(z2);
  Real z2 = sin(z1);
equation
  der(y) = time;
end ProfilingTest;

We simulate as usual, after setting the profiling flag:

>>> setCommandLineOptions("--profiling=blocks+html")
true
>>> simulate(ProfilingTest)
record SimulationResult
    resultFile = "«DOCHOME»/ProfilingTest_res.mat",
    simulationOptions = "startTime = 0.0, stopTime = 1.0, numberOfIntervals = 500, tolerance = 1e-06, method = 'dassl', fileNamePrefix = 'ProfilingTest', options = '', outputFormat = 'mat', variableFilter = '.*', cflags = '', simflags = ''",
    messages = "LOG_SUCCESS       | info    | The initialization finished successfully without homotopy method.
LOG_SUCCESS       | info    | The simulation finished successfully.
Warning: empty y range [1:1], adjusting to [0.99:1.01]
Warning: empty y range [1:1], adjusting to [0.99:1.01]
Warning: empty y range [1:1], adjusting to [0.99:1.01]
Warning: empty y range [1:1], adjusting to [0.99:1.01]
Warning: empty y range [1:1], adjusting to [0.99:1.01]
Warning: empty y range [1:1], adjusting to [0.99:1.01]
stdout            | info    | Time measurements are stored in ProfilingTest_prof.html (human-readable) and ProfilingTest_prof.xml (for XSL transforms or more details)
",
    timeFrontend = 0.010742731,
    timeBackend = 0.006077982,
    timeSimCode = 0.00146992,
    timeTemplates = 0.004098896,
    timeCompile = 0.414253508,
    timeSimulation = 0.06134737000000001,
    timeTotal = 0.498081549
end SimulationResult;
"Warning: There are nonlinear iteration variables with default zero start attribute found in NLSJac0. For more information set -d=initialization. In OMEdit Tools->Options->Simulation->OMCFlags, in OMNotebook call setCommandLineOptions("-d=initialization").
Warning: The initial conditions are not fully specified. For more information set -d=initialization. In OMEdit Tools->Options->Simulation->OMCFlags, in OMNotebook call setCommandLineOptions("-d=initialization").
"

Profiling information for ProfilingTest

Information

All times are measured using a real-time wall clock. This means context switching produces bad worst-case execution times (max times) for blocks. If you want better results, use a CPU-time clock or run the command using real-time priviliges (avoiding context switches).

Note that for blocks where the individual execution time is close to the accuracy of the real-time clock, the maximum measured time may deviate a lot from the average.

For more details, see ProfilingTest_prof.xml.

Settings

Name

Value

Integration method

dassl

Output format

mat

Output name

ProfilingTest_res.mat

Output size

24.0 kB

Profiling data

ProfilingTest_prof.data

Profiling size

0 B

Summary

Task

Time

Fraction

Pre-Initialization

0.000110

2.41%

Initialization

0.000133

2.92%

Event-handling

-0.000000

0.00%

Creating output file

0.000378

8.29%

Linearization

NaN%

Time steps

0.003310

72.56%

Overhead

0.000137

3.00%

Unknown

NaN

NaN%

Total simulation time

0.004562

100.00%

Global Steps

Steps

Total Time

Fractio n

Average Time

Max Time

Deviati on

|Graph thumbna il 999|

499

0.00331 0

72.56%

6.63326 6533066 13e-06

0.00008 2623

11.46x

Measured Function Calls

Name

Calls

Time

Fractio n

Max Time

Deviati on

|Graph thumbna il functio n fun0||Graph thumbna il count functio n fun0|

Profil ingTest .f _

506

0.00005 3434

1.17%

0.00000 0819

6.76x

Measured Blocks

Name

Calls

Time

Fractio n

Max Time

Deviati on

|Graph thumbna il eq0|| Graph thumbna il count eq0|

` <#eq0 >`__

7

0.00007 6642

1.68%

0.00007 7374

6.07x

|Graph thumbna il eq12||Graph thumbna il count eq12|

` <#eq1 2>`__

2

0.00000 2181

0.05%

0.00000 2303

1.11x

|Graph thumbna il eq20||Graph thumbna il count eq20|

` <#eq2 0>`__

504

0.00053 4919

11.73%

0.00001 1871

10.18x

|Graph thumbna il eq22||Graph thumbna il count eq22|

` <#eq2 2>`__

504

0.00073 7650

16.17%

0.00001 1340

6.75x

Equations

Name

Variables

eq0

eq1

y

eq2

s

eq3

eq4

z2

eq5

eq6

` <#var0>`__

eq7

` <#var0>`__

eq8

` <#var0>`__

eq9

` <#var0>`__

eq10

z1

eq11

eq12

x

eq13

der(y)

eq14

z2

eq15

eq16

` <#var0>`__

eq17

` <#var0>`__

eq18

` <#var0>`__

eq19

` <#var0>`__

eq20

z1

eq21

eq22

x

eq23

Variables

Name

Comment

y

der(y)

x

This is x

z1

z2

s

This report was generated by OpenModelica on 2020-09-29 08:50:24.

Genenerated JSON for the Example

Listing 6 ProfilingTest_prof.json
{
"name":"ProfilingTest",
"prefix":"ProfilingTest",
"date":"2020-09-29 08:50:24",
"method":"dassl",
"outputFormat":"mat",
"outputFilename":"ProfilingTest_res.mat",
"outputFilesize":24581,
"overheadTime":0.000181066,
"preinitTime":0.000110225,
"initTime":0.000132798,
"eventTime":-1.35525e-20,
"outputTime":0.000377593,
"jacobianTime":2.88931e-05,
"totalTime":0.00456161,
"totalStepsTime":6.05995e-06,
"totalTimeProfileBlocks":0.00135139,
"numStep":499,
"maxTime":8.2622949e-05,
"functions":[
{"name":"ProfilingTest.f","ncall":506,"time":0.000053434,"maxTime":0.000000819}
],
"profileBlocks":[
{"id":0,"ncall":7,"time":0.000076642,"maxTime":0.000077374},
{"id":12,"ncall":2,"time":0.000002181,"maxTime":0.000002303},
{"id":20,"ncall":504,"time":0.000534919,"maxTime":0.000011871},
{"id":22,"ncall":504,"time":0.000737650,"maxTime":0.000011340}
]
}

Using the Profiler from OMEdit

When running a simulation from OMEdit, it is possible to enable profiling information, which can be combined with the transformations browser.

Profiling setup

Figure 101 Setting up the profiler from OMEdit.

When profiling the DoublePendulum example from MSL, the following output in Figure 102 is a typical result. This information clearly shows which system takes longest to simulate (a linear system, where most of the time overhead probably comes from initializing LAPACK over and over).

Profiling results

Figure 102 Profiling results of the Modelica standard library DoublePendulum example, sorted by execution time.