Executing Simulation

One crop plan, a sequence of crop plans ending with a Stop event, or the entire Crop Plans worksheet may be executed. A group of Crop Plan worksheets may be executed sequentially using the Batch CP projections button found in the MGMTools menu on the MGM Toolbar. For more information on the operation and usage see the MGM workbook section.

What happens when you execute a growth simulation?

When a crop plan is executed, stand summary information is placed into other worksheets in the MGM workbook. Then, following the growth schedule, the tree list and other stand characteristics are repeatedly projected 1 year into the future by updating tree diameters, heights, and densities to reflect increment and mortality. At the end of each projection interval, information in the other worksheets is updated. This cycle continues until the growth schedule is completed.

Each event in the sequence of events (one or several crop plans) is executed sequentially until the last event is reached. During evaluation, several worksheets are updated as the projection proceeds including the Record, Stand, and Yields worksheets. Charts are not updated until all events have been processed.

The Excel Status Bar displays the name of the Crop Plan currently being projected. The longer the projection schedule, the more simulation time is required. Depending on the speed of your machine, this could be anywhere from less than one minute to 10 minutes or more depending on the complexity and number of crop plans being executed.

How are Crop Plan Options settings determined?

When a series of crop plans are executed, including executing the entire Crop Plans worksheet or a sequence of crop plans, the Options settings remain in effect until replaced by another Options event. For example, the Options event may be inserted before the first crop plan and it remains in effect for all subsequent crop plans unless another Options event is executed.

When a single crop plan is executed, most settings are taken from the events occurring within the Crop Plan itself. However, there are several exceptions to this rule:

  • If the Options event is not present in the crop plan, the most recent Options event above (towards the top of the worksheet) the crop plan will be
  • If there are any Notes above the current crop plan, they will be included in the Record file.

Making many projections: General considerations

MGM was not designed for projecting a great many stands, though enhanced computing resources are reducing concerns about computational speed. There are a number of approaches to processing a modest number of stands and Crop Plans. There is no limit on the number of Crop Plans, but excessively long processing time may become a factor when the number gets extremely large.

Processing multiple Crop Plans within one Crop Plans worksheet

The Crop Plans worksheet allows any number of individual crop plans to be processed. Development of the plans is relatively easy using the MGM Toolbar
buttons and also some Excel tools. For example, Crop Plans can be copied and pasted multiple times into the Crop Plans worksheet using the Excel Copy/Paste buttons. Editing the settings for individual events and initiating the projections is best handled using the MGM Toolbar.

Placing too many CP in the Crop Plans worksheet may provide too much detail and charts that become difficult to interpret. It is usually better to have a modest number of CP that have some common elements. Additional CP worksheets can be constructed, saved, and then executed at once using the Batch processing features described below.

Batch processing of multiple Crop Plans worksheets

Batch processing of one or more Crop Plans worksheets already saved into the MGM Crop Plans workbook is initiated by clicking the Batch CP projections button on the MGM Tools menu found on the MGM Toolbar. A dialog is presented from which one or more Crop Plans worksheets may be selected. Each of the selected worksheets is then processed without user input and the Record worksheets are automatically saved into the MGM Records workbook. Note that this overwrites any previous Record for the worksheets being processed.

Managing MGM projections from outside the MGM workbook

For advanced users, limited access to the MGM internal Excel Visual Basic for Applications (VBA) macros is permitted. These tools may be used to import CP worksheets, make projections, and save results using an external Excel workbook and Excel VBA programming tools. This ability allows greater flexibility for automating the preparation of data and Crop Plans as well as making the growth projections and saving results of Crop Plan projections. These features are described in VBA User Interface.

(NOT CURRENTLY IMPLEMENTED) Processing multiple external stands with the same Crop Plan

  • Stands may be created in external files provided they follow the tab-delimited format of the Stands worksheet. They can also be created using the Create Stand Dialog and then exported from the MGM Stands workbook.
  • The stands may be placed into any directory.
  • A special file "standlist.txt" must be placed in the same directory to list the names of stand files to be processed.
  • Finally, the Establish event in the Crop Plan must be edited to indicate the location of the sub-directory where the external stands are found.