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Fatal Error: Number of ObjectDef Alpha Args > Size of AlphaArg Array

asked 2016-08-15 15:32:01 -0500

Hi Energy Modeling Community,

I'm setting up a very simple co-simulation between EnergyPlus and a Functional Mockup Unit (FMU). The FMU is configured to return a fraction that would be fed into an OtherEquipment object as the Schedule Name input. For now I just wanted to report the result of the simulation to check if the communication is working. I used the EnergyPlus example 1ZoneUncontrolled to which I added the lines below.

ExternalInterface,
    FunctionalMockupUnitImport;  !- Name of External Interface

ExternalInterface:FunctionalMockupUnitImport,
    OtherEquipmentFraction.fmu,  !- FMU File Name
    15,                      !- FMU Timeout {ms}
    0;                       !- FMU LoggingOn

ExternalInterface:FunctionalMockupUnitImport:From:Variable,
    ZONE ONE,                !- Output:Variable Index Key Name
    Zone Outdoor Air Drybulb Temperature,  !- Output:Variable Name
    OtherEquipmentFraction.fmu,  !- FMU File Name
    OtherEquipmentFraction,  !- FMU Instance Name
    EnvironmentAirTemp;      !- FMU Variable Name

ExternalInterface:FunctionalMockupUnitImport:From:Variable,
    ZONE ONE,                !- Output:Variable Index Key Name
    Zone Mean Air Temperature,  !- Output:Variable Name
    OtherEquipmentFraction.fmu,  !- FMU File Name
    OtherEquipmentFraction,                !- FMU Instance Name
    ZoneAirTemp;             !- FMU Variable Name

ExternalInterface:FunctionalMockupUnitImport:To:Schedule,
    TEST352aNewPowerLevel,   !- Name
    Fraction,              !- Schedule Type Limits Names
    OtherEquipmentFraction.fmu,  !- FMU File Name
    OtherEquipmentFraction,                !- FMU Instance Name
    OEFraction,              !- FMU Variable Name
    1;                       !- Initial Value

Output:Variable,*,Schedule Value,hourly;

I have previously had this model working on EnergyPlus 8.1.0x86 but wanted to try using EnergyPlus 8.5.0x86. When I setup and run the simulation I receive the error:

**  Fatal  ** IP: GetObjectItem: ExternalInterface:FunctionalMockupUnitImport:To:Schedule, Number of ObjectDef Alpha Args [5] > Size of AlphaArg array [3].

I looked into ObjectDef Alpha Args and AlphaArg array and found a discussion of EnergyPlus's IDD file and the developer guide. Do I need to edit the IDD file in some way to support the FMU functionality I am attempting to use above? Should I use an older version of EnergyPlus?

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answered 2016-08-15 16:34:47 -0500

Archmage gravatar image

I think that error indicates a coding problem that you will not be able to get around by editing the IDD. You might send the input file to the energyplus helpdesk so the developers can follow up.

In looking at the code, I think you could add in any type of a schedule input object that has 5 or more alpha input fields and that will serve as a workaround for this issue. This is because the "AlphaArg" array sizes should be dynamic and adjust to the longest schedule input object.

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Thank you for your response. Excuse my ignorance but can you describe to me what an alpha input field is and how a schedule would have 5 or more? Does it have to do with how the ExternalInterface creates a dynamic schedule that in some ways grows during simulation? I decided to try another example file (SmOffPSZ) and found that the simple example in my question works. The problem seems to be isolated to the configuration employed in 1ZoneUncontrolled.idf

JustinShultz gravatar image JustinShultz  ( 2016-08-15 16:46:09 -0500 )edit
1

1ZoneUncontrolled does not have lots of schedules, the only one it has has only 2 alpha fields because it is the simplest constant schedule type. Alpha fields are text entries in an input object. The file SmOffPSZ has many schedules so it has the workaround.

Archmage gravatar image Archmage  ( 2016-08-15 17:12:51 -0500 )edit

Oh okay, that makes sense to me now. Thank you for answering my questions!

JustinShultz gravatar image JustinShultz  ( 2016-08-15 17:32:58 -0500 )edit

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Asked: 2016-08-15 15:32:01 -0500

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Last updated: Aug 15 '16