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At first glance each of the above scenarios seems very different. Some of the examples work with already running engines while others dynamically launch engines. Some work with local engines while others connect to engines running on a different machine. Despite these differences, they all use the same basic logic to accomplish their tasks. Therefore, it will be well worth the effort to build a generic or “black box” system for working with multiple engines. This white paper will help you to design this foundation.
Getting Started Anchor Getting Started Getting Started
| Getting Started | |
| Getting Started |
Our intent is to provide you everything you need in this document to begin designing applications capable of using multiple engines. Nevertheless, you might be interested in getting a copy of the previously mentioned OI 4.1 New Features.pdf document. In some areas it has more detail regarding the new OpenEngine which might be helpful to programmers who desire to dig a little deeper.
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Once RemoteRequest has successfully executed our process, it is our responsibility to monitor the status of the remote engine. Two functions are available for this: WaitForReply and PollForReply. In the Getting the Big Picture chart above only PollForReply is mentioned. This is because WaitForReply does exactly what its name implies; that is, it waits for a reply from the remote engine before proceeding. Therefore, if our remote process is busy performing a long process then our local engine will be forced to wait until it is completed. Actually, to be technically correct, if the remote process uses the Send_Info or Send_Dyn commands to send information back then WaitForReply will allow the local engine to receive it. WaitForReply must then be called again to wait for the next information update or until the remote process has completed. Because many processes do not use Send_Dyn or Send_Info (like RList selects), WaitForReply is only a little better than using CallFunction or CallSubroutine.
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Whenever any of our functions returns a value other than 0 we need to compare this with the list of errors from the Error Definitions (REVCERRS.H) file (see the [[1]]the References section below for a complete list.) Here is a portion of code that can be used:
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With this final piece tied together you now have a “black box” approach toward managing remote engines. While this does not exhaust all that is possible with remote engines, we believe this will give many applications a significant enhancement boost in functionality. We hope that you will agree.
References Anchor References References
| References | |
| References |
Further information we think will be helpful are listed here for your convenience:
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