Changes between Initial Version and Version 7 of Ticket #5934


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Timestamp:
2020-05-05T23:20:11Z (5 years ago)
Author:
Philip Hannebohm
Comment:

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  • Ticket #5934

    • Property Cc Francesco Casella added
    • Property Priority low → high

  • Ticket #5934 – Description

    initial v7  
    55In cases like {{{der(y^x)}}} this may even result in pretty ugly residual equations.
    66
    7 Instead we could introduce an alias {{{z = sin(x)*y}}}, s.t. {{{der(z) = 1}}}. I believe Karim has some convincing arguments towards this approach. I'll try to recap them from what I understand:
    8 a. If {{{x}}} and {{{y}}} appear only algebraically elsewhere, introducing an alias results in fewer states, thus a lower index.
     7Instead we could introduce an auxiliary variable {{{$aux = sin(x)*y}}}, s.t. {{{der($aux) = 1}}}. I believe Karim has some convincing arguments towards this approach. I'll try to recap them from what I understand:
     8a. If {{{x}}} and {{{y}}} appear only algebraically elsewhere, introducing an auxiliary results in fewer states, thus a lower index.
    99b. Otherwise ({{{der(x)}}} and {{{der(y)}}} exist elsewhere) the system may need index reduction anyways, because the states {{{x}}} and {{{y}}} are connected somehow. The alias might allow index reduction to pick a better choice.
    1010