Design Space Explorer (DSE) Design Example

Design Space Explorer (DSE) is a simple and easy-to-use design optimization utility that ships with the Quartus^® II software. DSE explores and reports Quartus II options that are optimal for your design and targets design performance, area utilization, or power dissipation improvements.

DSE searches through a predefined set of Quartus II options that make it easy to determine optimal settings for a particular design.

In this design example you will do the following steps:

• Explore available DSE options
• Learn how to use DSE to find the best settings for a sample design
• Understand how to interpret the DSE report file

This example was developed using the Quartus II software version 9.0 SP1 running on a PC. This archived design example has an OpenCore Ethernet MAC instance targeted to a Cyclone^® III device. The core is constrained within a LogicLock^TM region in the selected device.

Default Compilation

To run the default compilation, perform the following steps:

1. Download the MAC_top.qar project archive file and save it to your computer.
2. Start Quartus II GUI and un-archive the design. Restore the archived project MAC_top_for_dse.qar file by selecting the Restore Archived Project option under the Project menu, and pointing to the archive file location.
3. Use the default directory name prompted in the dialog box, and click OK.
4. Compile the project with default settings by choosing Start Compilation under the Processing menu. You can also click on the Explore     icon on the Quartus II GUI to compile the design. The compilation takes a few minutes to complete.
5. After the compilation is complete, open the Compilation Report panel by selecting Compilation Report from the Processing menu of the Quartus II GUI. Click on the + sign next to TimeQuest Timing Analyzer report section under the compilation report to view timing failures. You will see that the design has setup violations on the Clk_user and Clk_125M domain, and hold violations on Rx_clk the domain. Here are the expected screenshots for setup summary and hold summary.

This is the base compilation for this design, and clearly it does not meet timing.

Run a DSE Exploration

Now run a DSE exploration to determine best settings for this design with the following steps:

1. From the Tools menu of the Quartus II GUI, select Launch Design Space Explorer. Click on Yes when prompted. This closes the Quartus II GUI and starts the DSE GUI.
2. From the Options menu on the DSE GUI, turn on the following options:

Your options selection should match the following screenshot.

3. On the Project Settings page under the Settings tab, check the Project Uses Quartus II Integrated Synthesis option.
4. In the seeds fields, type in two values: 1 and 2 separated by a white space. Seeds affect the initial random placement. We are using 2 seed values here for our exploration. (In general, using more than one seed value helps us determine if changes in results are due to changes in settings and not due to some randomness in the Fitter algorithms.)
5. Select Search for Best Performance option.
6. For the effort level, select Selective (Selected Performance Optimizations). This is likely to minimize exploration time. Your exploration options should look like the following screenshot.

7. Start exploring the design with DSE, by clicking on the Explore  icon on the GUI. By default, results of DSE exploration are saved in the directory named dse under your project directory.

The time for DSE exploration depends on the compute resources available on your machine.

Understand the DSE Report File

In this DSE exploration example, the compilation point 9 gives a result that meets all timing constraints. Since we have chosen to stop exploration after zero failing paths have been reached, the DSE exploration ends after compiling the 9^th compilation point. On the DSE GUI, you get a visual indication of which compilation point the DSE is working on.

After the DSE exploration is complete, open the DSE report file from the DSE GUI by selecting View Last DSE Report for Project from the Processing  menu. The DSE report summarizes the results and the compilation settings for all the compilation points in the DSE run. A section of the DSE report that compares the base compilation settings and the best compilation settings in the following screenshot.

The results.csv file in the dse directory under the project directory contains the timing results from all the compilation points in the exploration space. The best compilation is flagged in the .csv file too

Design Examples Disclaimer

These design examples may only be used within Altera Corporation devices and remain the property of Altera. They are being provided on an “as-is” basis and as an accommodation; therefore, all warranties, representations, or guarantees of any kind (whether express, implied, or statutory) including, without limitation, warranties of merchantability, non-infringement, or fitness for a particular purpose, are specifically disclaimed. Altera expressly does not recommend, suggest, or require that these examples be used in combination with any other product not provided by Altera.