Determining When to Use Reentrant or Non-Reentrant SubVIs

You can configure a subVI as reentrant or non-reentrant. By default, subVIs created under an FPGA target are reentrant. The following table provides recommendations for specific use cases.

SubVI Type Design
Reentrant Use when a subVI does not access shared resources, such as I/O.
Non-reentrant Use when a subVI accesses shared resources.
Non-reentrant Use when multiple instances of a subVI share data in a VI, such as functional global variables.

For other design implementations, use the estimated device utilization and timing reports from the Reports pull-down menu of the Compilation Status window to verify which subVI configuration meets the needs of your FPGA application. The Compilation Status window appears after you compile an FPGA VI. You may need to iterate several times before finding the subVI type that works best for your application.