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Merging, Diverging, and Routing Flow
Features of the Merge and Diverge blocks
Competing Requests for Flow model
This model demon- strates how the pri- orities in two routing blocks com- pete against each other.
In this example:
• The Diverge
block’s outflow
branch priorities
have been speci-
fied in descend-
ing order while
the Merge blocks'
inflow branch pri-
orities have been specified ascending order.
• The two blocks share common flow streams.
While the Diverge block in this model will try to satisfy its top outflow branch first, the Merge block will oppose that by trying to satisfy its bottom inflow branch. To resolve this conflict, the Diverge block's priorities have been biased over the Merge block. This was accomplished by selecting Each block defines its own bias order in the Discrete Rate tab of the Executive block, then selecting the Diverge block in the Executive’s table and entering a bias of 1.
Selecting the option “Show bias order on icon” in the Discrete Rate tab of the Executive block causes the bias value to be displayed near block icons as “<x>”. In the above model, the bias order is indicated as <1> for the Diverge block and <2> for the Merge block, indicating that the Diverge block has precedence over the Merge block’s requests.
☞ To see how the Bias block is used instead of Merge/Diverge blocks to resolve competing pref- erences for flow, see the “Prioritize With Bias Blocks” model located in the folder \Exam- ples\Discrete Rate\Merge and Diverge and discussed on page 432.
Managing flow attributes
When flow is merged or diverged, the management of flow attributes is based on settings in the dialogs of the Merge and Diverge blocks.
The Flow Attributes tab of the Merge and Diverge blocks has several options that determine how attribute values are handled when flow is merged or diverged. Default behaviors for layer and string layer attributes are specified separately.
Whichever option is selected becomes the default option for that type of flow as it passes through the block. For exceptions to the default, the blocks provide a table for specifying cus- tom behavior for each attribute.
Internal throw and catch
While the Rate library has two blocks, Throw Flow and Catch Flow, specifically designed to transport flow without the use of connection lines, the Diverge and Merge blocks have been
Competing Requests for Flow model
Discrete Rate

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