reset_example_6_variablesastestvalues.rst

Example: Using variables as test values

Description: A simple example showing the behaviour when a reset test value is given by a variable.

Note that:

• all elements are in the same component;
• the order values of resets are not shown; and
• all variables have dimensionless units.

component: 
  ├─ math: 
  │   └─ ode(A, t) = 1
  │
  ├─ variable: A initially 1
  │
  └─ variable: B initially 2
      └─ reset: 
          ├─ when B == A
          └─ then B = B + 1

See CellML syntax

<variable name="t" units="dimensionless" />
<variable name="A" units="dimensionless" initial_value="1" />
<variable name="B" units="dimensionless" initial_value="2" />

<math>
    <apply><eq/>
        <diff>
            <ci>B</ci>
            <bvar>t</bvar>
        </diff>
        <cn cellml:units="dimensionless">1</cn>
    </apply>
</math>

<reset variable="B" test_variable="B">
    <test_value>
        <ci>A</ci>
    </test_value>
    <!-- Variable B is given a value of B+1 when B equals A. -->
    <reset_value>
        <apply><plus/>
            <ci>B</ci>
            <cn cellml:units="dimensionless">1</cn>
        </apply>
    </reset_value>
</reset>

At t = 1 the following situation occurs:

t	0	0.1	...	1
A	1	1.1	...	2
B	2	2	...	2

The reset for B is now active, leading to the following update:

t	0	0.1	...	1
A	1	1.1	...	2
B	2	2	...	2 → 3

A change has been made, so a second cycle of evaluations is started. No resets are found to be active (B no longer equals A), and so model dynamics continue.

t	0	0.1	...	1	1.1	...	2	2.1
A	1	1.1	...	2	2.1	...	3	3.1
B	2	2	...	2 → 3	3	3	3 → 4	4

At t = 2 the reset rule is triggered a second time, in a similar fashion.