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WaterGEMS Water Age analysis - different results when running on different computers?

We are running a model of a large network (20,000 customers, and including 40 tanks plus a large number of pumps and control valves).

Every time we run the model for water age (running a 90-day EPS), we seem to get a different set of results for the water age in the tank. In most cases the difference is only in the order of one day or so, but sometimes it's up to 9-10 days. We have done a number of tests (changing nothing but the location of the file) and it looks like each time the model is run on a different computer, the results are different, but if we keep to the one computer then they are the same.

This inability to replicate the same result each time is causing us (and our client) some concern, so I'm just after some more detail about how the water age is calculated and whether this is a known or expected result? Is there an element of randomisation in the calculation?

Thanks, Liz

  • Hello Liz,

    Are both computers, that you've run the model on, using the same version of WaterGEMS and patch set? Check the date and version number by going to Help > About WaterGEMS.

    Where in the model are you seeing a difference in calculated age?

    Try the suggestions in the following article.
    How can I troubleshoot my model when my water age results don't appear correct?

    If that doesn't help then please provide the model as explained in the following article.
    Sharing Hydraulic Model Files on the Haestad Forum

     

    Regards,

    Craig Calvin

    Bentley Technical Support

  • Also, are both computers running the same bitness (32-bit vs 64-bit)?

     

    Regards,

    Craig Calvin

    Bentley Technical Support

  • Regarding bitness - you can check this in the Welcome dialog if using CONNECT Edition, or under File>Help>About (or Help>About, if using CONNECT Edition). You should see "32-bit" or "64-bit" next to the version number in the lower-left corner.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • Hi Craig,

    We have now tested this across five different computers, all running the same version and patch set (08.11.05.61 1/08/14) and all 64-bit. I do realise that this is not the latest version of the software but we are restricted in that we cannot upgrade until our client does given that the software is not back-compatible to older versions.

    The post regarding troubleshooting incorrect results does not help us at this stage, as it’s not that the results are incorrect/unexpected, it’s that they are completely different. In all five cases we took a copy of the model from the network location, saved it to the local drive and ran the same scenarios without changing a thing, then graphed the water age in all tanks. By the end of a 90-day simulation the water age is different by up to ten days in some tanks in three out of five models (three produced the same result, with two others different). We then checked the processors used by each computer, and this does not help us – two computers with the same processor produced different results whereas two different processors gave matching results. This is true across multiple scenarios. We have not yet run similar tests across other models from previous projects but are considering doing so to determine whether the problem is more widespread.

    Whilst we could look at the “three-out-of-five” result and assume that this is the correct answer, we are still concerned and not keen to make recommendations to our client with regards to water quality treatment requirements on this basis. We run models on the basis that the results are always repeatable, and this isn't proving to be the case.

    I'm in the process of uploading the files to Bentley server - file is named "Rev4.zip" with reference made to this thread.
  • The .zip you provided contains the .wtg and .dwh model files.
    Please provide the .wtg and .sqlite model files.

     

    Regards,

    Craig Calvin

    Bentley Technical Support