= Description =
To simulate chemical or biological process in Diana the Initial Value Problem should be solved at first. A guess for initial conditions can be set in model file. [[BR]] Standard {{{ IDACalcIC() }}} method of Sundials package can calculate consistent initial conditions for homogeneous differential algebraic equations systems of the type

{{{
#!html
<table border="0" width="50%" align="center">
<tr>
  <td align = "center" fontsize ="50%" width="90%">
  dx<sub>1</sub>/dt = f<sub>1</sub>(x<sub>1</sub>, x<sub>2</sub>, ..., x<sub>n</sub>, t)<br>
  dx<sub>2</sub>/dt = f<sub>2</sub>(x<sub>1</sub>, x<sub>2</sub>, ..., x<sub>n</sub>, t)<br>
             ...            <br>
  dx<sub>n</sub>/dt = f<sub>n</sub>(x<sub>1</sub>, x<sub>2</sub>, ..., x<sub>n</sub>, t)
  </td>
  <td align="center">(1)
  </td>
</tr>
</table>
}}}

But in case of non-homogeneous differential algebraic equations systems of the type

{{{
#!html
<table border="0" width="50%" align="center">
<tr>
  <td align = "center" fontsize ="50%" width="90%">
  F<sub>1</sub>(dx<sub>1</sub>/dt, dx<sub>2</sub>/dt, ..., dx<sub>n</sub>/dt) = f<sub>1</sub>(x<sub>1</sub>, x<sub>2</sub>, ..., x<sub>n</sub>, t)<br>
  F<sub>2</sub>(dx<sub>1</sub>/dt, dx<sub>2</sub>/dt, ..., dx<sub>n</sub>/dt) = f<sub>2</sub>(x<sub>1</sub>, x<sub>2</sub>, ..., x<sub>n</sub>, t)<br>
             ...            <br>
  F<sub>n</sub>(dx<sub>1</sub>/dt, dx<sub>2</sub>/dt, ..., dx<sub>n</sub>/dt) = f<sub>n</sub>(x<sub>1</sub>, x<sub>2</sub>, ..., x<sub>n</sub>, t)
  </td>
  <td align="center">(2)
  </td>
</tr>
</table>
}}}

{{{IDACalcIC()}}} generates the exception
{{{
   ECapeUnknown in IDASolver (Diana) startIntegrator, IDACalcIC failed
}}}

Consistent initial conditions for differential algebraic equations system  of type (2) can be found with {{{IDACalcIC()}}} method, but the system should be manually changed to form (1) before.[[BR]]
'''''ICSolver''''' can calculate initial conditions for systems of the type (2) without any conversions of the system.

= Example =

[attachment:AdsColumn.mdl "Adsorption column model"] contains the equations system of type (2) example[[BR]]
[attachment:AdsColumn_error.py "Python script with calling standard IDACalcIC() method"] generates the exception[[BR]]
[attachment:AdsColumn.py "Python script with using ICSolver and nonzero output verbosity level"] shows the initial state vector and message

{{{
   ICSolver: Consistent initial conditions have been found
}}}

== Additional information ==

{{{ eso.GetAllVariables() }}} returns state vector values of equation set object[[BR]]
{{{ eso.GetAllResiduals() }}} returns vector of right hand side values of equations system with current values of state vector[[BR]]
''Note: With correct state vector initial values all residuals of equation set object should be equal to zeros''

== Additional examples ==

 * Hafke reactor[[BR]]
   [attachment:HafkeReactor.py "script"] [attachment:HafkeReactor.tar "script + model + results"]

 * Cstr model[[BR]]
   [attachment:Cstr.py "script"] [attachment:Cstr.tar "script + model + results"]

 * MATLAB example[[BR]]
   [attachment:matlab.tar "files"]