Parameterisation

First Order Parameters

To define a variable, the user uses curly braces in a comment line within the MCNP input.

Plain text
Copy
1c { var1 = 1 }

Complex variables can span multiple lines, provided there is a starting comment card on each line.

Plain text
Copy
1c { var1
2c =
3c 1 }

To use a parameter in the MCNP input, substitute the variable name enclosed by curly braces (cannot be used in a comment card).

Plain text
Copy
11 PX {var1}
22 RPP -{var1} {var1} -50 50 {var2} {var3}

Mathematical operations can be performed when defining a variable, or in the evaluation of the variable at substitution time, for example.

Plain text
Copy
11 PX {var1 + sin(1.25)}

Second Order Parameters

Variables can depend on other variables, and can involve mathematical operations, as follows:

Plain text
Copy
1c { var2 = var1 + 1.0 }

Range Parameters

A range variable can be defined in several ways, with the most common method using commas, for instance.

Plain text
Copy
1c { var1 = 1.0, 2.0, 3.0, 4.0 }

A second way to define a range is with colons, where the first value is the starting value, the second value is the stop-before value, and the third value is the increment value.

Plain text
Copy
1c { var1 = 1 : 10 : 2 }

This is the equivalent of:

Plain text
Copy
1c { var1 = 1, 3, 5, 7, 9 }

When more than one range is present, Cyclone will create files for every possible variable combination, for example.

Plain text
Copy
1c { var1 = 10.0, 20.0, 30.0 }
2c { var2 = 40.0, 50.0, 60.0 }

This will generate the following files with var1 and var2 expanded as follows:

Plain text
Copy
1Input 1: var1=10, var2=40
2Input 2: var1=10, var2=50
3Input 3: var1=10, var2=60
4Input 4: var1=20, var2=40
5Input 5: var1=20, var2=50
6Input 6: var1=20, var2=60
7Input 7: var1=30, var2=40
8Input 8: var1=30, var2=50
9Input 9: var1=30, var2=60

Sometimes it is not desirable to generate inputs for every possible combination; instead, it is desirable to step through variable ranges one at a time. To instruct Cyclone to step through a range, use $ to separate the values, instead of using a comma.

Plain text
Copy
1c { var1 = 10.0$ 20.0$ 30.0 }
2c { var2 = 40.0$ 50.0$ 60.0 }
3c { var3 = 70.0$ 80.0$ 90.0 }

Will generate the following input files:

Plain text
Copy
1Input 1: var1=10, var2=40, var3=70
2Input 2: var1=20, var2=50, var3=80
3Input 3: var1=30, var2=60, var3=90

Currently, range parameters are limited to “first order”; that is, they cannot contain another variable.

For example, the following usage is not permitted:

Plain text
Copy
1c { var1 = var2, var3, var4, var5 }

Preprocessors

Cyclone provides a basic preprocessor that can handle if-else statements. These preprocessors must appear at the beginning of a line and cannot be placed behind a comment sign. The preprocessors are defined as follows:

Plain text
Copy
1|IF {variable} {expressions} {expression answer}
2|ELSE IF {variable} {expressions} {expression answer} or
3|ELIF {variable} {expressions} {expression answer}
4|ELSE
5|ENDIF

For example:

Plain text
Copy
1|IF var1 == 8
21 px 8
3|ELSE IF var1 == 9
41 px 9
5|ELSE IF var1 == 10, 11, 12 #eg var1 is either 10, 11 or 12
61 px 10
7|ELSE IF var1 > 12
81 px 15
9|ELSE
101 px 7
11|ENDIF

There is no limit to the number of lines that can be used within the if-else blocks; the only limitation is that variables cannot be defined within these blocks.

Expressions

Expressions can be simple:

Plain text
Copy
1c { var1 = 1 }

Or they can be complex ternary operations:

Plain text
Copy
1c { var2 = var1 > 10 ? 25 : 5 }

Multiple nested ternary operations are also possible:

Plain text
Copy
1c { var3 = var2 > 10 ? 25 : var1 < 10 ? 15 : 5 }

The more complicated the function becomes, the harder it is to read, so it is advisable to use multi-line inputs.

Booleans

Boolean logic can be applied to preprocessor macros or ternary operations, see Table 1.

In-Operator

The '==' operator can also be used to check if a variable is equal to a value in an array, for example:

Plain text
Copy
1var1 == 1, 2, 3, 40, 50, 60

This would return true if var1 is one of the values; otherwise, it would return false. The in-operator can be used in the preprocessors or ternary statements.

The user cannot use a range variable to compare against, however other variables can be used.

This is allowed:

Plain text
Copy
1var1 == var2, var3, 40, 50, 60

This is NOT allowed:

Plain text
Copy
1{var2 = 1, 2, 3, 40, 50, 60}
2var1 == var2

Random and Seed Values

Random and Seed variables can be used. To define a random variable, the user can either use random(upper) to produce a random number between 0 and the upper value, or they can use randint(lower, upper) to generate a random integer between lower and upper. By default, the seed is set to an integer value. If the user needs to set the seed value to replicate runs, they can set the seed via:

Plain text
Copy
1c { seed = 123456 }

The seed value used is printed in the MCNP outputs.

Significant Figures

By default, the number of significant figures is set to 5. While local changes can be made on the substitution line with the following extension to the string substitution

Plain text
Copy
1{ var1, SFIG=0 }

This would effectively change var1 to an integer in this case.

Maths Symbols and Functions

Table 2 shows the full list of available math symbols and Table 3 shows the full list of available math functions that can be used in defining variables.

Naming Convention

It is strongly recommended to use a sensible name when creating parameters that are easy to understand in the context of any MCNP input. The user should not use numbers in naming variables, and a name that matches any of the available mathematical functions cannot be used; doing so will result in a parameterisation error.

Changing View Parameters

Parametrised models can be viewed in the 2D and 3D views. A Change Parameter button will appear in the Code Editor toolbar that allows the user to modify the viewed model and set of parameters if range parameters are used. See Figure 30.

CSV Parameter File

For large and complex models with many parameters, the input can become difficult to manage. To simplify this, a CSV file can be supplied containing a list of all required first-order parameters. The first line of the CSV file defines the variable names, and each subsequent line specifies a new input, with the variables read from that line.

Plain text
Copy
1var1, var2, var3, var4, var5, var6
21,2,3,4,5,6
37,8,9,10,11,12
413,14,15,16,17,18
519,20,21,22,23,24

This produces 4 inputs where the values of variables 1-6 change for each input.

Parameters used internally to Cyclone

Cyclone has a list of parameters that are used internally and can be added to executable commands or the queue template used with the remote server, see Table 4 for a full list of parameters. Appendix 1 shows how to use them in the remote server template.

Figure 30: Change view parameters

Table 1: Boolean Logic | Logic | Evaluation | |-------|----------------------------------------------------------| | == | Checks if two arguments are the same | | >= | Checks if the first argument is equal to or greater than | | <= | Checks if the first argument is equal to or less than | | > | Checks if the first argument is equal to or less than | | < | Checks if the first argument is less than |

Table 2: Math Symbols | Symbol | Details | Symbol | Details | |--------|------------------------------|---------|---------------------------| | + | Addition | - | Subtraction | | * | Multiplication | / | Division | | ^ | To the power of | % | Modulus | | () | Parenthesis | & | And | | | | Or | = | Equals | | > | Greater than | < | Less than | | >= | Greater than or equal to | <= | Less than or equal to |

Table 3: Available Math Functions

Table 4: Cyclone Backend Symbols