Softmax update

[bugracyln]

Description

📝 Please include a summary of the change.

The softmax table generation logic was updated. The implementation for writing the softmax tables was revised, and memory attributes were added to enable a more efficient FPGA compilation flow. In addition, the templates were modified to use weights directly from the configuration.

• Please also include relevant motivation and context.

The primary motivation for these changes was to bring the oneAPI backend closer to the Vivado backend in terms of implementation.

Memory attributes were added to enable memory banking on the FPGA, allowing for more efficient memory access. The weights are now copied directly into the configuration so that the compiler can recognise the entire table as a set of fixed values. This enables the memory to be implemented more efficiently, resulting in improved resource utilisation during FPGA compilation.

• List any dependencies that are required for this change.

N/A

Type of change

For a new feature or function, please create an issue first to discuss it
with us before submitting a pull request.

Note: Please delete options that are not relevant.

• Bug fix (non-breaking change that fixes an issue)
• Documentation update
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)
• A new research paper code implementation
• Other (Specify)

Tests

📝 Please describe the tests that you ran to verify your changes.

The changes were primarily verified using black-box tests on an isolated softmax unit. Testing was performed for both quantised and non-quantised implementations. For the quantised version, both configurations, with and without exp and inv table quantisers (QuantiserConfig(...)), were tested.

Additional testing included:

• Generating FPGA RTL reports.
• Building the emulator.
• Performing a hardware compilation using the new Intel oneAPI compiler.

This PR currently supports only the Intel oneAPI compiler. Support for the Altera HLS compiler will be added in a future PR.

The implementation was also evaluated with different table sizes, and the resulting RTL reports were inspected to verify improvements in resource utilisation.

• Provide instructions so we can reproduce.

A Python test file and a Keras model containing only a single softmax layer (Softmax or QSoftmax) were used. For the quantised implementation, the input and output quantisers for the exp and inv lookup tables were configured using QuantiserConfig(...). Tests were run with both the quantisers enabled and disabled.

The test configuration included:

• Standard Softmax and QSoftmax models.
• Explicit exp and inv table input output quantisation.
• FPGA RTL generation.
• Emulator build.
• Hardware compilation with the Altera HLS (newer version of Intel oneAPI)compiler.

• Please also list any relevant details for your test configuration.

Test Configuration:

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.

[jmitrevs]

We should probably squash the commits when merging. This should also be coordinated with #1476. We should see how best to do that.

[JanFSchulte]

Could we also get any form of description of what this is? I was about to close it as spam before I noticed that this was related to work by Lauri.

[calad0i]

About to close it as spam also if not seeing the please-test tag... Could you add some descriptions?