# External interfaces » advanced in-line coding in Strurel

STRUREL supports the following five external engines: Matlab, Python, Maple, Mathematica and Ruby. In previous posts, we discussed exemplarily for Matlab and Python how in-line code and external scripts can be evaluated with STRUREL. In case computational performance matters, external scripts should be preferred over in-line code, as in-line code needs to be re-processed each time a limit-state function is evaluated.

Nevertheless, for testing purposes you might prefer to simply work with in-line code in STRUREL. For multi-line code, you can split-up your code as is shown in the following Python-based example:

FLIM(1) = pythonf("%import math")
+ pythonf("%A=math.sqrt(R)")
+ pythonf("R-S+A")

Note that the individual pythonf-calls are connected by a ‘+’. However, except for the actual limit-state function call R-S+A, all code-lines start with a ‘%’. This character is interpreted by STRUREL and not forwarded to the external engine (Python in the example above). The ‘%’ at the beginning of a code line tells STRUREL that the associated line of code does NOT return a value. In the example above, both R and S are random variables defined through STRUREL.

# Use a Python script as limit-state function

In one of the previous posts, we showed you how to work with in-line Python functions directly in STRUREL. Did you know? You can also use a Python script as limit-state function in STRUREL.

Again, we use the example limit-state function RS that we already used in the past: Our stochastic model consists of the two random variables R and S, where R represents the resistance of a system of interest and S is the system load. The symbolic expression for the corresponding limit-state function in the native syntax of STRUREL would be:

FLIM(1) = R-S

However, if you have Python installed on your system and if the Python interface of STRUREL is configured correctly, you could also use the following expression:

FLIM(1) = pythons("my_model")

where my_model.py is a Pyhton script file located in the same directory as the iti-file of STRUREL.

For the example at hand, the Python script file should look as follows:

res = R - S

where the variable names R and S must match the names of the random variables of the stochastic model of STRUREL. The variable res must contain the value of the limit-state function, where the value of res is later retrieved by STRUREL.

By means of the STRUREL command pythons, you can integrate any limit-state function written in Python directly in your reliability analysis performed with STRUREL.

# Use a Matlab script as limit-state function

In one of the previous posts, we showed you how to work with in-line Matlab functions directly in STRUREL. Did you know? You can also use a Matlab script as limit-state function in STRUREL.

Again, we use the example limit-state function RS that we already used in the past: Our stochastic model consists of the two random variables R and S, where R represents the resistance of a system of interest and S is the system load. The symbolic expression for the corresponding limit-state function in the native syntax of STRUREL would be:

FLIM(1) = R-S

However, if you have Matlab installed on your system and if the Matlab interface of STRUREL is configured correctly, you could also use the following expression:

FLIM(1) = matlabs("my_model")

where my_model.m is a Matlab script file located in the same directory as the iti-file of STRUREL.

For the example at hand, the Matlab script file should look as follows:

function [lsfval] = my_model(INPUT)

R = INPUT(1);
S = INPUT(2);

lsfval = R - S

end

The ordering of the random variables in the vector INPUT corresponds to the order in which they appear in the stochastic model of STRUREL.

Alternatively, the Matlab script file could look as follows:

function [lsfval] = my_model(INPUT)

global R;
global S;

lsfval = R - S

end

where the variable names R and S must match the names of the random variables of the stochastic model of STRUREL.

By means of the STRUREL command matlabs, you can integrate any limit-state function written in Matlab-Syntax directly in your reliability analysis performed with STRUREL.

# How to use in-line Matlab in Strurel

In the last post, we showed you how to work with in-line Python functions directly in STRUREL. Did you know? You can also use in-line Matlab functions directly in a symbolic expression in STRUREL.

For example, assume a problem for which you have the two random variables R and S in your stochastic model, where R represents the resistance of a system of interest and S is the system load. The symbolic expression for the corresponding limit-state function in the native syntax of STRUREL would be:

FLIM(1) = R-S

However, if you have Matlab installed on your system and if the Matlab interface of STRUREL is configured correctly, you could also use the following expression:

FLIM(1) = matlabf("R-S")

Sure, calling the Matlab interpreter for this simple demonstration example is like taking a sledgehammer to crack a nut. However, the interface-function matlabf is a tool that gives you access to the full power of Matlab directly in the symbolic expression of STRUREL.

# How to use in-line Python in Strurel

Did you know? You can use in-line Python functions directly in a symbolic expression in STRUREL.

For example, assume a problem for which you have the two random variables R and S in your stochastic model, where R represents the resistance of a system of interest and S is the system load. The symbolic expression for the corresponding limit-state function in the native syntax of STRUREL would be:

FLIM(1) = R-S

However, if you have Python installed on your system and if the Python interface of Strurel is configured correctly, you could also use the following expression:

FLIM(1) = pythonf("R-S")

Sure, calling the Python interpreter for this simple demonstration example is like taking a sledgehammer to crack a nut. However, the interface-function pythonf is a tool that gives you access to the full power of Python directly in the symbolic expression of Strurel.