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Coercing Array Types in Optimized FPGA VIs

Last Modified: March 30, 2016

Coercing array data types can increase the latency and initiation intervals of an Optimized FPGA VI.

If you see latency or initiation intervals that are higher than expected or desired in your Optimized FPGA VI, check for warnings about coercing array types. The coercion of data types in an array results in a larger performance hit than non-array data type coercions. LabVIEW uses coercion dots to identify code where data type coercion occurs.

Adjust your code to avoid coercing array data types whenever possible. If you can't avoid coercing the data type of an array, convert red coercion dots to blue coercion dots for better performance.

Select the node and set the data type on the Item tab to the same data type as the downstream terminal. The red coercion dot on the downstream terminal disappears. A blue coercion dot appears on the node to indicate that the fixed-point configuration is manually set and the output data type will not adjust automatically to avoid overflow and rounding errors.

Examples

In the following example, the data type of Increment outputs as I9 <4.5>, resulting in a red coercion dot at the downstream output terminal of Replace Array Subset.

In the following example, the red coercion dot from the previous example is changed to a blue coercion dot on the output of Increment by setting the data type of Increment to I8 <3.5>. Matching the data type of the node and the downstream output terminal results in better performance.

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