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Reducing Long Estimation Times in Optimized FPGA VIs

Last Modified: August 9, 2019

The compiler explores multiple possibilities for the most efficient implementation of an Optimized FPGA VI on hardware. Exploring the possibilities can lead to long estimation times.

If it takes longer than ten minutes to estimate the Optimized FPGA VI, utilize any combination of the following strategies to reduce the load on the compiler and speed up the estimation.
Strategy Description
Keep loop iterations low

Loops that iterate more than 10,000 times significantly increase estimation times and can sometimes prevent successful compilation.

To address unnecessarily high loop iterations, remove loops from Optimized FPGA VIs when the loop is not part of the algorithm. For example, if you need to run an algorithm through a large sample set, call the Optimized FPGA VI from a loop located in a top-level VI instead of incorporating a loop in the algorithm design.

Share an array across multiple loops

If your Optimized FPGA VI has multiple loops, share a common array input across the loops to achieve the fastest estimation times.


If the loops in your VI cannot share a common array, keep the loops in separate Optimized FPGA VIs to reduce the possible combinations of loop unrolling factors that the compiler optimizes for.

Adjust the throughput and FPGA resource budget

Throughput and the FPGA resource budget affect the amount of exploration the compiler performs as it tries to find the fastest solution that meets both the throughput and the resource constraints.

To reduce estimation time, increase the FPGA resource budget or lower the specified throughput. You can adjust the throughput and routing margin using the estimation options in the following locations:

  • On the Item tab when you select an Optimized FPGA VI integration node from the diagram of a top-level FPGA VI.
  • From the VI Estimation dialog box that appears when you click FPGA Estimates on the Document tab in an Optimized FPGA VI.
Reduce the number of cases in a Case Structure Implementing Case Structures with more than 50 cases tends to lead to long estimation times. Reduce the number of cases in a Case Structure or reorganize a Case Structure into nested Case Structures to reduce estimation time.

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