Lsd main Manual

Using a Lsd Model

Introduction

The best way to learn to use a Lsd model is, like any software, to try and err. In the following is presented a tutorial listing the main steps in using a Lsd model, as guideline to start using Lsd models. The goal of a simulation exercise is to obtain interesting results and understand why they have been produced. Therefore it is not sufficient to obtain fancy graphs, but it is also necessary to get into the code of the model, and understand its functioning. After this tutorial you should be able to fully exploit an existing model, and to explore the Lsd interfaces even in the parts not explicitly covered here. Refer to the main Lsd manual for a complete description of the Lsd interfaces.

To run a simulation exercise with Lsd it is used:

a Lsd model program. This is a program mixing the C++ code implementing equations for a model and the general Lsd code. The modeller has created the code for the equations, and users cannot modify it by running the model program.
a model configuration. This is the definition of the model prepared by the modeller. It contains the description in terms of entities (Objects), Variables and Parameters. The configuration contains also all the necessary information used to run a simulation: the number of Objects, the initial values for Parameters, the number of time steps, etc. Users can easily modify each of these values to test different configurations.

Using Lsd entails the access to several windows, and sometime the one to use is hidden behind other ones. It is strongly advised to make use of the icon bar to access the window needed.

The table below consists of three columns:

Operation, summary of the operation to perform;
Progr. indicates the software to use: LMM (Lsd Model Manager, which is supposed to be running before starting this tutorial); Lsd; Netsc. (Netscape, or any web browser);
Menu choices and Comments The beginning of this cell contains always the operation to perform (the menu choices are written in bold), and then follow comments and explanations.

To use the tutorial you should run LMM, from the main manu Start of windows, or from clicking on its icon. Unix users need to locate the directory where it is installed and run ./lmm.

Now you can follow the steps indicated below. Using the program indicated in the Instr. column follow the instruction at the top of any cell in the right column. The text in bold indicates either a relevant window or a menu and the menu entry to choose: menu/menu_entry. Many windows will pop up during this exercise, partly from the program used, part from new Netscape windows if you click on a link. Use the icon bar of your screen to retrive the program you want to access.

Operation Progr. Menu choices and Comments

Run the Lsd model program LMM

Model/Select

Model/Run

Choose the model you want to explore using menu Model/Select Model, and then run the corresponding Lsd model program. LMM automatically starts the Lsd model program for you (ensuring that it has been properly compiled). If LMM cannot run the model, for example because the compilation fails, a log window informs you with the reasons of the failures. See the help page on possible problems.
When Lsd starts, it shows two windows, Browser and Log. The model interfaces are initially empty, since no configuration is loaded.

Load a configuration file Lsd

File/Load

Choose one of the proposed files with extension ".lsd". A model configuration contains the model description, the initial data, and everything it is required to run a simulation. The modeller has prepared at least one configuration, and more can be created with the Lsd interfaces.
The Lsd Browser now shows the Object Root as containing some elements. A graphical representation of the model is shown in a new window. The Browser is thought as a control center to issue commands to the Lsd model program, and as the inspector for one Object type. The Browser is always pointed on an Object, and lists its Variables and the contained Objects.
IMPORTANT: Close the windows using their buttons or keyboards shortcuts. Killing a window closes the whole Lsd model program.

Give a first look to the model Lsd

See the structure of the model

Help/Model Help

Help/Model Report

Although you may already run a simulation, spend some time to look at how Lsd represents a model.
The "scheleton" of the model are Objects, elements containing Parameters, Variables, or other Objects. Therefore, a model is represented by a hierarchy of Objects, whose "top" element is conventionally called Root. Root is the only Object that is always present in a model with a single instance, while the other Objects can be multiplied in as many instances as desired. Actually, the number of instances for each Object type is a parameter stored in the configuration file. Users can change these values, as we will see later.
Variables and Parameters are labels attached with numbers. The obvious difference is that Variables can change values at each time step using a specific equation, while Parameters don't have an equation (although an equation for a Variable can overwrite the value of a Parameter). The goal of Objects in Lsd models is to contain Variables: multiplying the number of Objects, also all the Variables and the Parameters contained in that Object type are multiplied. This is similar to using vectors, but it is more efficient, and permits to easily create hierarchies. See the Lsd FAQ's for more details.
It is possible to explore the model with the Browser (square window on the top left part of the screen), which shows one single Object's content. This is shown with some headers and two list boxes: Variables (and Parameters) and the Descendants, Objects contained in that type of Object. Variables are indicated with a integer number (the lagged values used in the model for that Variable), and Parameters are indicated with the letter "P". Variables labels can also be double-clicked to set their options and see their documentation (see below).
The Browser can be moved from one Object to another double-clicking on the descendants of an Object (to go "down") or on the name of the Object's "parent" (to go "up"). You can also use the arrows to move along Objects and Variables.
Another representation of the model is shown (on the right of the Browser) in a symbolic format. It shows the hierarchy of the Objects and indicates also the number of copies, or instances, for each Object type. Moving the mouse pointer over the symbol for one Objects makes appear a small window listing the Variables and Parameters contained in the Object. It is possible to click on the symbol of an Object in the graphical representation of the model to move there with the Browser.
Besides showing the content of an Object, the main Browser is the interface of the Lsd model program. From its manus it is possible to change the configuration, run a simulation launch the analysis of results, etc.

The structure of a model and the exact role of each item (Object, Variable or Parameter) depends not only from its own content, but also from its relation with the rest of the model. To better grasp this aspect Lsd models offer the Model Reports. These may
The most detailed information on the model is contained in two documents prepared by the modellers: the model help and the model report. These are two HTML documents that appear in your system web browser (e.g. Netscape), when selecting their command in the menu Help of the Browser.
The model report is the most useful documentation of the model. It contains all the information presented in such a way to provide very quickly any information requested. Its links permit to see:

each Object with its content;

where each element is used (e.g the Variables using a Parameter)

which elements are used (e.g. which Parameters are used in a Variable's equation

For each Variable is also reported the actual C++ code used for the Variable, where the model elements in the code are links to their own section in the model report. For non expert programmers the code is provided with a brief description (represented as comment).
Spend some time to "play" with the links of the model report, to see how they show the model content. Do not try, at least for complex models, to read systematically the document and to understand the whole model structure. Just start from one component, look at its equations, or the equations that use it, and continue along creating your own path through the model structure.
The model help contains the list of the model element, possibly with a verbal descriptions prepared by the modeller. The model report contains the actual code used for the equations and other relevant information on the model structure. The two documents contain links to each other bringing at your attention all the relevant information for each element of the model.

Model Report Lsd The structure of a model and the exact role of each item (Object, Variable or Parameter) depends not only from its own content, but also from its relation with the rest of the model. To better grasp this aspect Lsd models offer the Model Reports. These standard HTML documents that can be opened using the menu Help/Model Report.
(It is possible that for some model configuration the Model Report is not available, which is indicated by an error message appearing when trying to open it. In this case you can create the report with two commands. Choose the command in menu Mode/Generate Automatic Description and after that the command in menu Model/Create Report, accepting the default options.)
The reports are extremely useful to understand how the model works. They contain an introductory section with a verbal description of the model and three sections reporting:

Summary: list of all Objects, Variables and Parameters indicating where they are used (that is, in which equation their label appear), and possibly a verbal description of their functioning.

Initial Values: list of all Objects, Variables and Parameters reporting the initial values used at the start of the simulation (Variables never used with a lag do not appear here since they don't have initial values).

Details: list of all Objects, Variables and Parameters reporting the actual code for Variables' equations, items used, and other information.

Each item in each section contains links to their location in the other sections, so that the report can be easily browsed to understand the working of a model even without a full understanding of the actual code used in the equations. Test the report trying to understand some part of the model.

Run a simulation Lsd

Run/Run

Observe the Run Time Plot

Run a simulation exercise accepting all the default initialization defined by the modeller. Before running the symulation, the system issues a confirmation message listing the options used for the simulation.
A simulation run consist in several time steps, during each of which all the Variables of the models are updated, using their equations to compute the new values.
During the simulation run some Variables may be plotted in a self-scaling window called Run Time Plot, if the configuration is set for this. If no Variable is set to be plotted during the simulation (the so-called Run Time Plot), the Log window prints a line for each time step completed. More series are saved in the memory for later analysis (but not all data produced by the model at every time step are saved by default).
During a simulation it is possible to use the buttons in the Log window:

Stop: abort the simulation

Fast: make run the simulation faster not issuing any message, if possible (to accellerate the simulation minimize the Run Time Plot window, if exists)

Observe: run the simulation in normal (message issuing) mode, if requested by the configuration.

Debug: interrupt the simulation when an equation marked to be debugged is computed. The simulation run may be resumed after that.

Help: help on the Log window

Analyse the results Lsd

Data/Analysis of Results

The Run Time Plot may have given you some intuition of the simulation results. However, the modeller is likely to have set more data to be saved, besides the ones shown at run time. In fact, Lsd models allow to choose the Variables and Parameters values to be saved for later analysis.
This command makes available the data stored in memory after a simulation run, or previously saved on a file (when requested choose Simulation for using the data from the latest exercise, or File to get data from a file). It permits to observe in detail the series of the simulation.
The overall structure of this module is to list the elements available for analysis on the left box. Some of these must be selected and moved to the central box for elaboration, activated with the buttons in the lower part of the window. The right box contains the list of the graphs produced. Try to explore the data available (see here for the manual on this topic).
There is a large number of possible options to produce time series, cross-section or XY scatter plot graphs. Moreover, users can produce statistics on the data available and save data files in a variety of formats. It is also possible to launch gnuplot, a package for function and data-plotting (Lsd distribution for Windows contains also Gnuplot for Windows, while Unix users are expected to already have it).
See carefully the manual for this module to fully exploit its functionalities.

Interpret the results Lsd
and
Netsc.

plot graphs and statistics of the simulation data (See here for the manual)

use Model Report to make sense of the series' meaning

Search in the documentation the elements of interest and look at their functioning in the model to understand the reasons for ther results obtained. In fact, in the section Summary of the report it is either contained the verbal description of the Variable computation or, in case of a Parameter, it is at least indicated the Variable(s) that may have changed its values.
When finished, exit the Analysis of Result module with the menu Exit.

Reload the configuration Lsd

File/Reload

Reset the model to contain again the values for beginning a simulation.
After a simulation exercise Lsd contains in memory the values computed at the last time step. The system prevents the use of these values as the starting values of a new simulation run, and therefore a new configuration must be loaded.
Note that it is possible to save the model status as new configuration, which can be loaded to continue a simulation exercise.

Edit the number of instances
for the Objects Lsd

Data/Set Number of Objects/All types of Objects

Modify the number of Objects.
One obvious request to test a simulation model is to modify the number of Objects (and therefore the number of Variables, Parameters and other Objects they contain).
With this interface it is possible to modify any group of Objects, always maintaining the same model structure (i.e. the new Objects at higher level in the hierarchy will contain the same type of descending Objects at lower levels. But there will be, by default, only one instance of such descending Objects). See the Lsd help on this.
When finished, click on Exit to the return to the Browser.

Edit the initial values Lsd

Browse the model

Data/Init. Values

Change the initial values used to start a simulation.
When starting a simulation Lsd needs to know the values to assign to the Parameters. Moreover, the models usually contain Variables used with past values, that must be inserted for use in the very first steps of the simulation. This command allows users to modify such values, for one Object type. Note that the hierarchical structure of the Lsd models forces to use multi-digit indexing to identify the Object instance containing a given Parameter or lagged Variable value.
The initialization of values is requested also for the Objects created when modifying the number of Objects. They are assigned a default value (copied from the very first instance of that type of Object in the model), but usually the user may want to modify this.
Although the data may be inserted manually, when there are very many values it is convenient to use the Set All button to set all the initial values for a single line.
See the Lsd manual on this.
When finished, click on Ok to return to the Browser.

Edit the simulation settings Lsd

Run/Sim. Settings

Choose the number of time step per simulation, the seed for the random generator, and number of simulation exercises to be run in a sequence (each with the same initialization values and different random generator seed). See the Lsd manual on this.
Note that running more than a simulation exercise cause the system to save the data in files.

Edit the choices on which
series to save, to plot
at run time, or to debug Lsd

Browse the model

double-click on the Variable of interest

For each Variables and Parameters it is possible to decide whether:

it must be included in the data saved for analysis after a simulation (To Save)

it must appear in the Run Time Plot, to observe its values during the simulation run (Run Time Plot)

it should cause the simulation to be interrupted immediately after its equation has been computed (Debug). Only for Variables

This options are passed in the configuration file, but it is possible to change them (saving too many data makes the simulation slower).
See the Lsd manual on this.
These choices can also be changed individually for each element, or can be set off for the whole model using Remove ... in menu Run.

Save the configuration Lsd

File/Save

A modified configuration should be saved with a different name from the configuration loaded before the changes since, when running a simulation, the system overwrites the original configuration loaded with the new options.

Run the newly configured model Lsd

Run/Run

It is possible that an attempt to run a modified model does not succeed. The system prevents running model configurations not adapt, issuing messages to fix the errors (some message can be printed in the Log window, that may be hiddeen behind the graphical representation). Typical errors are:

model already run. The configuration is derived from the last step of a simulation exercise, and not from a "fresh" configuration file. Load a new configuration, makes the changes as indicated above, save the configuration with a new name, and finally run the newly configured model.

data non initialized. If the number of Objects is increased, then the newly created instances contain Parameters and lagged Variables that must be initialized before they can be used for a simulation run. Move the Browser to point to the Object indicated in the error message (in the Log window) and choose Data/Init. Values.

It is also possible some configurations are initialized with non-consistent values, causing, for example, divisions by zero during the computation of some equation. The simulation results are, in these cases, erratic, and may even cause sudden crashes of Lsd. To avoid this keep always a copy of a working configuration, and try few changes per time.

Test other aspects of Lsd Lsd

Any menu, any entry

Explore any menu entry of the Browser (see the help on the Browser). As general advice:

the menu Model modifies the structure of the model, and should be used only by modellers since it likely entails modifications of the equations' code;

remember that when running a simulation the configuration is written on file, overwriting the last configuration loaded with the same name;

keep open the Lsd help pages, explaining in detail the effects of any operation

Open another model LMM

Model/Select

Model/Run

After closing the current model, try another model and follow the same instructions to appreciate the differences (and the common interfaces) between two Lsd models.

Create your own model LMM As you have seen, using an existing model permit to modify every numerical aspect of the simulation, but you are constrained to keep the model structure (Objects, Variables and Parameters) and the equations unchanged. This is because the structure influences the way the equations compute their values for the Variables. And the equations are implemented as compiled code within the Lsd model program. Follow the tutorial 3 to learn to create a new Lsd model.

Operation	Progr.	Menu choices and Comments
Run the Lsd model program	LMM	Model/Select Model/Run Choose the model you want to explore using menu Model/Select Model, and then run the corresponding Lsd model program. LMM automatically starts the Lsd model program for you (ensuring that it has been properly compiled). If LMM cannot run the model, for example because the compilation fails, a log window informs you with the reasons of the failures. See the help page on possible problems. When Lsd starts, it shows two windows, Browser and Log. The model interfaces are initially empty, since no configuration is loaded.
Load a configuration file	Lsd	File/Load Choose one of the proposed files with extension ".lsd". A model configuration contains the model description, the initial data, and everything it is required to run a simulation. The modeller has prepared at least one configuration, and more can be created with the Lsd interfaces. The Lsd Browser now shows the Object Root as containing some elements. A graphical representation of the model is shown in a new window. The Browser is thought as a control center to issue commands to the Lsd model program, and as the inspector for one Object type. The Browser is always pointed on an Object, and lists its Variables and the contained Objects. IMPORTANT: Close the windows using their buttons or keyboards shortcuts. Killing a window closes the whole Lsd model program.
Give a first look to the model	Lsd	See the structure of the model Help/Model Help Help/Model Report Although you may already run a simulation, spend some time to look at how Lsd represents a model. The "scheleton" of the model are Objects, elements containing Parameters, Variables, or other Objects. Therefore, a model is represented by a hierarchy of Objects, whose "top" element is conventionally called Root. Root is the only Object that is always present in a model with a single instance, while the other Objects can be multiplied in as many instances as desired. Actually, the number of instances for each Object type is a parameter stored in the configuration file. Users can change these values, as we will see later. Variables and Parameters are labels attached with numbers. The obvious difference is that Variables can change values at each time step using a specific equation, while Parameters don't have an equation (although an equation for a Variable can overwrite the value of a Parameter). The goal of Objects in Lsd models is to contain Variables: multiplying the number of Objects, also all the Variables and the Parameters contained in that Object type are multiplied. This is similar to using vectors, but it is more efficient, and permits to easily create hierarchies. See the Lsd FAQ's for more details. It is possible to explore the model with the Browser (square window on the top left part of the screen), which shows one single Object's content. This is shown with some headers and two list boxes: Variables (and Parameters) and the Descendants, Objects contained in that type of Object. Variables are indicated with a integer number (the lagged values used in the model for that Variable), and Parameters are indicated with the letter "P". Variables labels can also be double-clicked to set their options and see their documentation (see below). The Browser can be moved from one Object to another double-clicking on the descendants of an Object (to go "down") or on the name of the Object's "parent" (to go "up"). You can also use the arrows to move along Objects and Variables. Another representation of the model is shown (on the right of the Browser) in a symbolic format. It shows the hierarchy of the Objects and indicates also the number of copies, or instances, for each Object type. Moving the mouse pointer over the symbol for one Objects makes appear a small window listing the Variables and Parameters contained in the Object. It is possible to click on the symbol of an Object in the graphical representation of the model to move there with the Browser. Besides showing the content of an Object, the main Browser is the interface of the Lsd model program. From its manus it is possible to change the configuration, run a simulation launch the analysis of results, etc. The structure of a model and the exact role of each item (Object, Variable or Parameter) depends not only from its own content, but also from its relation with the rest of the model. To better grasp this aspect Lsd models offer the Model Reports. These may The most detailed information on the model is contained in two documents prepared by the modellers: the model help and the model report. These are two HTML documents that appear in your system web browser (e.g. Netscape), when selecting their command in the menu Help of the Browser. The model report is the most useful documentation of the model. It contains all the information presented in such a way to provide very quickly any information requested. Its links permit to see: each Object with its content; where each element is used (e.g the Variables using a Parameter) which elements are used (e.g. which Parameters are used in a Variable's equation For each Variable is also reported the actual C++ code used for the Variable, where the model elements in the code are links to their own section in the model report. For non expert programmers the code is provided with a brief description (represented as comment). Spend some time to "play" with the links of the model report, to see how they show the model content. Do not try, at least for complex models, to read systematically the document and to understand the whole model structure. Just start from one component, look at its equations, or the equations that use it, and continue along creating your own path through the model structure. The model help contains the list of the model element, possibly with a verbal descriptions prepared by the modeller. The model report contains the actual code used for the equations and other relevant information on the model structure. The two documents contain links to each other bringing at your attention all the relevant information for each element of the model.
Model Report	Lsd	The structure of a model and the exact role of each item (Object, Variable or Parameter) depends not only from its own content, but also from its relation with the rest of the model. To better grasp this aspect Lsd models offer the Model Reports. These standard HTML documents that can be opened using the menu Help/Model Report. (It is possible that for some model configuration the Model Report is not available, which is indicated by an error message appearing when trying to open it. In this case you can create the report with two commands. Choose the command in menu Mode/Generate Automatic Description and after that the command in menu Model/Create Report, accepting the default options.) The reports are extremely useful to understand how the model works. They contain an introductory section with a verbal description of the model and three sections reporting: Summary: list of all Objects, Variables and Parameters indicating where they are used (that is, in which equation their label appear), and possibly a verbal description of their functioning. Initial Values: list of all Objects, Variables and Parameters reporting the initial values used at the start of the simulation (Variables never used with a lag do not appear here since they don't have initial values). Details: list of all Objects, Variables and Parameters reporting the actual code for Variables' equations, items used, and other information. Each item in each section contains links to their location in the other sections, so that the report can be easily browsed to understand the working of a model even without a full understanding of the actual code used in the equations. Test the report trying to understand some part of the model.
Run a simulation	Lsd	Run/Run Observe the Run Time Plot Run a simulation exercise accepting all the default initialization defined by the modeller. Before running the symulation, the system issues a confirmation message listing the options used for the simulation. A simulation run consist in several time steps, during each of which all the Variables of the models are updated, using their equations to compute the new values. During the simulation run some Variables may be plotted in a self-scaling window called Run Time Plot, if the configuration is set for this. If no Variable is set to be plotted during the simulation (the so-called Run Time Plot), the Log window prints a line for each time step completed. More series are saved in the memory for later analysis (but not all data produced by the model at every time step are saved by default). During a simulation it is possible to use the buttons in the Log window: Stop: abort the simulation Fast: make run the simulation faster not issuing any message, if possible (to accellerate the simulation minimize the Run Time Plot window, if exists) Observe: run the simulation in normal (message issuing) mode, if requested by the configuration. Debug: interrupt the simulation when an equation marked to be debugged is computed. The simulation run may be resumed after that. Help: help on the Log window
Analyse the results	Lsd	Data/Analysis of Results The Run Time Plot may have given you some intuition of the simulation results. However, the modeller is likely to have set more data to be saved, besides the ones shown at run time. In fact, Lsd models allow to choose the Variables and Parameters values to be saved for later analysis. This command makes available the data stored in memory after a simulation run, or previously saved on a file (when requested choose Simulation for using the data from the latest exercise, or File to get data from a file). It permits to observe in detail the series of the simulation. The overall structure of this module is to list the elements available for analysis on the left box. Some of these must be selected and moved to the central box for elaboration, activated with the buttons in the lower part of the window. The right box contains the list of the graphs produced. Try to explore the data available (see here for the manual on this topic). There is a large number of possible options to produce time series, cross-section or XY scatter plot graphs. Moreover, users can produce statistics on the data available and save data files in a variety of formats. It is also possible to launch gnuplot, a package for function and data-plotting (Lsd distribution for Windows contains also Gnuplot for Windows, while Unix users are expected to already have it). See carefully the manual for this module to fully exploit its functionalities.
Interpret the results	Lsd and Netsc.	plot graphs and statistics of the simulation data (See here for the manual) use Model Report to make sense of the series' meaning Search in the documentation the elements of interest and look at their functioning in the model to understand the reasons for ther results obtained. In fact, in the section Summary of the report it is either contained the verbal description of the Variable computation or, in case of a Parameter, it is at least indicated the Variable(s) that may have changed its values. When finished, exit the Analysis of Result module with the menu Exit.
Reload the configuration	Lsd	File/Reload Reset the model to contain again the values for beginning a simulation. After a simulation exercise Lsd contains in memory the values computed at the last time step. The system prevents the use of these values as the starting values of a new simulation run, and therefore a new configuration must be loaded. Note that it is possible to save the model status as new configuration, which can be loaded to continue a simulation exercise.
Edit the number of instances for the Objects	Lsd	Data/Set Number of Objects/All types of Objects Modify the number of Objects. One obvious request to test a simulation model is to modify the number of Objects (and therefore the number of Variables, Parameters and other Objects they contain). With this interface it is possible to modify any group of Objects, always maintaining the same model structure (i.e. the new Objects at higher level in the hierarchy will contain the same type of descending Objects at lower levels. But there will be, by default, only one instance of such descending Objects). See the Lsd help on this. When finished, click on Exit to the return to the Browser.
Edit the initial values	Lsd	Browse the model Data/Init. Values Change the initial values used to start a simulation. When starting a simulation Lsd needs to know the values to assign to the Parameters. Moreover, the models usually contain Variables used with past values, that must be inserted for use in the very first steps of the simulation. This command allows users to modify such values, for one Object type. Note that the hierarchical structure of the Lsd models forces to use multi-digit indexing to identify the Object instance containing a given Parameter or lagged Variable value. The initialization of values is requested also for the Objects created when modifying the number of Objects. They are assigned a default value (copied from the very first instance of that type of Object in the model), but usually the user may want to modify this. Although the data may be inserted manually, when there are very many values it is convenient to use the Set All button to set all the initial values for a single line. See the Lsd manual on this. When finished, click on Ok to return to the Browser.
Edit the simulation settings	Lsd	Run/Sim. Settings Choose the number of time step per simulation, the seed for the random generator, and number of simulation exercises to be run in a sequence (each with the same initialization values and different random generator seed). See the Lsd manual on this. Note that running more than a simulation exercise cause the system to save the data in files.
Edit the choices on which series to save, to plot at run time, or to debug	Lsd	Browse the model double-click on the Variable of interest For each Variables and Parameters it is possible to decide whether: it must be included in the data saved for analysis after a simulation (To Save) it must appear in the Run Time Plot, to observe its values during the simulation run (Run Time Plot) it should cause the simulation to be interrupted immediately after its equation has been computed (Debug). Only for Variables This options are passed in the configuration file, but it is possible to change them (saving too many data makes the simulation slower). See the Lsd manual on this. These choices can also be changed individually for each element, or can be set off for the whole model using Remove ... in menu Run.
Save the configuration	Lsd	File/Save A modified configuration should be saved with a different name from the configuration loaded before the changes since, when running a simulation, the system overwrites the original configuration loaded with the new options.
Run the newly configured model	Lsd	Run/Run It is possible that an attempt to run a modified model does not succeed. The system prevents running model configurations not adapt, issuing messages to fix the errors (some message can be printed in the Log window, that may be hiddeen behind the graphical representation). Typical errors are: model already run. The configuration is derived from the last step of a simulation exercise, and not from a "fresh" configuration file. Load a new configuration, makes the changes as indicated above, save the configuration with a new name, and finally run the newly configured model. data non initialized. If the number of Objects is increased, then the newly created instances contain Parameters and lagged Variables that must be initialized before they can be used for a simulation run. Move the Browser to point to the Object indicated in the error message (in the Log window) and choose Data/Init. Values. It is also possible some configurations are initialized with non-consistent values, causing, for example, divisions by zero during the computation of some equation. The simulation results are, in these cases, erratic, and may even cause sudden crashes of Lsd. To avoid this keep always a copy of a working configuration, and try few changes per time.
Test other aspects of Lsd	Lsd	Any menu, any entry Explore any menu entry of the Browser (see the help on the Browser). As general advice: the menu Model modifies the structure of the model, and should be used only by modellers since it likely entails modifications of the equations' code; remember that when running a simulation the configuration is written on file, overwriting the last configuration loaded with the same name; keep open the Lsd help pages, explaining in detail the effects of any operation
Open another model	LMM	Model/Select Model/Run After closing the current model, try another model and follow the same instructions to appreciate the differences (and the common interfaces) between two Lsd models.
Create your own model	LMM	As you have seen, using an existing model permit to modify every numerical aspect of the simulation, but you are constrained to keep the model structure (Objects, Variables and Parameters) and the equations unchanged. This is because the structure influences the way the equations compute their values for the Variables. And the equations are implemented as compiled code within the Lsd model program. Follow the tutorial 3 to learn to create a new Lsd model.