Cyclus Defined Constants

Cyclus defines a set of constants to help standardize archetype properties and prevent unexpected simulation failures. These constants are determined at build time and may depend on your system’s architecture (specifically the size of an int type, in bytes). This set is defined twice, with identical values existing in the C++ namespace and Python library. The numeric values are as follows:

Name	Value
CY_LARGE_INT	2147483647 on most 64-bit machines. This should be equal to std::numeric_limits<int>::max().
CY_LARGE_DOUBLE	1e299
CY_NEAR_ZERO	1e-08

Accessing constants in C++

The constants are defined in cyclus/cyc_limits.h and exist in the cyclus:: namespace. They can be used in this way:

#include "cyclus.h"
...
int my_large_int = cyclus::CY_LARGE_INT;
...

Accessing constants in Python

The constants are defined in the cyclus.system module and can be imported and used as long as the cyclus package is in your Python path:

from cyclus.system import CY_LARGE_DOUBLE, CY_LARGE_INT, CY_NEAR_ZERO
...
my_small_value = CY_NEAR_ZERO
...

This holds true for Cyclus input files:

from cyclus.system import CY_LARGE_DOUBLE
SIMULATION = { 'simulation':
  ...
  'facility': [
    { 'config':
      { 'Source':
        { 'capacity': CY_LARGE_DOUBLE,
  ...

Warning

Only input files written in Python can access the constants in this way, since the variables are evaluated prior to schema validation. Any attempt to use them in an XML input file will likely fail schema validation since they will be evaluated as strings instead of the corresponding values in C++/Python.

Using constants with the Cyclus Preprocessor

Many archetype developers utilize the Cyclus Preprocessor and #pragma cyclus to define state variables within an archetype. The preprocessor allows any arbitrary Python code to be executed via #pragma cyclus exec. Thus one can import the set of Python constants into the global namespace that agent annotations are processed, and reference them in state variable definitions. Remember that the object following #pragma cyclus var is evaluated by the Python interpreter, so you can treat it as if it were Python code.

#pragma cyclus exec from cyclus.system import CY_LARGE_DOUBLE

...

#pragma cyclus var {"default": CY_LARGE_DOUBLE, \
                  "tooltip": "sink maximum inventory size", \
                  "uilabel": "Maximum Inventory", \
                  "uitype": "range", \
                  "range": [0.0, CY_LARGE_DOUBLE], \
                  "doc": "total maximum inventory size of sink facility"}
double max_inv_size;