id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
2864	Replace homotopy with actual expression in non-initial sections	Martin Sjölund	Lennart Ochel	"We need to replace homotopy with actual expression in non-initial sections since the expression cannot be simplified or differentiated properly unless you do so. ModelicaTest 3.2.1: ModelicaTest.Fluid.TestComponents.Vessels.TestVolume gives the following error:

{{{#!mo
Notification: Model statistics after passing the front-end and creating the data structures used by the back-end:
 * Number of equations: 151
 * Number of variables: 151
[/var/lib/hudson/jobs/OpenModelica_TEST_ALL_LIBRARIES/workspace/OpenModelica/build/lib/omlibrary/Modelica 3.2.1/Fluid/Vessels.mo:358:11-391:17:writable] Error: Internal error 
Differentiate.differentiateEquationTime failed for 0.0 = if Volume.regularFlow[2] then Volume.ports[2].p - homotopy(Volume.medium.p + 0.5 * Volume.portAreas[2] ^ -2.0 * Modelica.Fluid.Utilities.regSquare2(-1.0, Volume.m_flow_small, (-1.0 + Volume.portsData[2].zeta_in + (Volume.portAreas[2] / 2.593327596953829) ^ 2.0) * Volume.ports_penetration[2] / Volume.portInDensities[2], (1.0 + Volume.portsData[2].zeta_out - (Volume.portAreas[2] / 2.593327596953829) ^ 2.0) / (Volume.ports_penetration[2] * Volume.medium.d), false, 1.0), Volume.medium.p) else if Volume.inFlow[2] then Volume.ports[2].p - Volume.medium.p else -1.0
Error: Internal error - IndexReduction.pantelidesIndexReduction1 failed! Use +d=bltdump to get more information.
Error: Internal error - IndexReduction.pantelidesIndexReduction failed!
Error: Internal error Transformation Module PFPlusExt index Reduction Method Pantelides failed!
}}}

See also #2751 for similar issues with keeping initial parts in the non-initial partitions."	defect	closed	high	1.9.4	Backend	trunk	fixed