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 = 0.010765037,
    timeBackend = 0.007882426,
    timeSimCode = 0.002035348,
    timeTemplates = 0.013227937,
    timeCompile = 0.5082890600000001,
    timeSimulation = 0.093917705,
    timeTotal = 0.636241492
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	0.000137	1.28%
Initialization	0.000149	1.40%
Event-handling	0.000000	0.00%
Creating output file	0.000858	8.03%
Linearization		NaN%
Time steps	0.008060	75.47%
Overhead	0.000227	2.13%
Unknown	NaN	NaN%
Total simulation time	0.010680	100.00%

Global Steps¶

	Steps	Total Time	Fractio n	Average Time	Max Time	Deviati on
\|Graph thumbna il 999\|	499	0.00806 0	75.47%	0.00001 6152304 6092184	0.00015 0997	8.35x

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	0.00014 5274	1.36%	0.00000 4412	14.37x

Measured Blocks¶

	Name	Calls	Time	Fractio n	Max Time	Deviati on
\|Graph thumbna il eq0\|\| Graph thumbna il count eq0\|	` <#eq0 >`__	7	0.00007 8492	0.73%	0.00008 0412	6.17x
\|Graph thumbna il eq12\|\|Graph thumbna il count eq12\|	` <#eq1 2>`__	2	0.00000 4644	0.04%	0.00000 4964	1.14x
\|Graph thumbna il eq20\|\|Graph thumbna il count eq20\|	` <#eq2 0>`__	504	0.00103 2220	9.66%	0.00001 9530	8.54x
\|Graph thumbna il eq22\|\|Graph thumbna il count eq22\|	` <#eq2 2>`__	504	0.00169 6890	15.89%	0.00002 0988	5.23x

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 2020-07-01 13:33:58.

Genenerated JSON for the Example¶

Listing 7 ProfilingTest_prof.json¶

{
"name":"ProfilingTest",
"prefix":"ProfilingTest",
"date":"2020-07-01 13:33:58",
"method":"dassl",
"outputFormat":"mat",
"outputFilename":"ProfilingTest_res.mat",
"outputFilesize":24581,
"overheadTime":0.000356413,
"preinitTime":0.000137015,
"initTime":0.000148797,
"eventTime":0,
"outputTime":0.000858057,
"jacobianTime":7.14342e-05,
"totalTime":0.01068,
"totalStepsTime":1.5436e-05,
"totalTimeProfileBlocks":0.00281225,
"numStep":499,
"maxTime":0.000150997009,
"functions":[
{"name":"ProfilingTest.f","ncall":506,"time":0.000145274,"maxTime":0.000004412}
],
"profileBlocks":[
{"id":0,"ncall":7,"time":0.000078492,"maxTime":0.000080412},
{"id":12,"ncall":2,"time":0.000004644,"maxTime":0.000004964},
{"id":20,"ncall":504,"time":0.001032220,"maxTime":0.000019530},
{"id":22,"ncall":504,"time":0.001696890,"maxTime":0.000020988}
]
}

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.

Figure 100 Setting up the profiler from OMEdit.¶

When profiling the DoublePendulum example from MSL, the following output in Figure 101 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).

Figure 101 Profiling results of the Modelica standard library DoublePendulum example, sorted by execution time.¶