Fix GlobalPooling1D Layers

[jmduarte]

Address #398

Test script (to be turned into a real test): https://gist.github.com/jmduarte/99aee1eee92524ad3b1dbf5c5a863296

Changes to do:

• Fix parsing of configuration for GlobalPooling1D layers
• Add global_pooling1d_cl io_stream HLS implementation
• Add global_pooling1d_cl io_parallel HLS implementation
• Add testing module

@jmitrevs

[jmitrevs]

One issue discovered while creating the tests is that io_stream GlobalAveragePooling has a tendency to overflow when doing the sum. Unlike the io_parallel implementation, it does not use a wider accumulator size. I am trying to see what is the best way to fix this.

[jmitrevs]

I added a test (and also an include of nnet_dense.h in nn_conv_stream.h). For the average overflow issue, one can manually increase the bit width of the layer (as done in test_globalpooling1d.py). I am not sure if it is better to automatically choose a wider width, but #327 made me wonder if it was best to leave it for the user. Let me know what you think we should do.

[jmduarte]

@thesps if you could review this, that'd be great. I think it's ready, except for perhaps creating an optimizer that would set accum_t for io_stream (mimicking the way it's currently handed in the HLS for io_parallel):

hls4ml/hls4ml/templates/vivado/nnet_utils/nnet_pooling.h

Line 35 in 4564916

ap_fixed<W + ceillog2(N), I + ceillog2(N)> tmp = 0;

[thesps]

Thanks, looks good to me now! On the point about setting the accumulator type - the automated setting of the accumulator type would be a good follow up, but I think what we have here is already good enough to merge since the type can be configured properly in any case.

I just changed the directory name that the test writes to from hls4ml_... to hls4mlprj... like the other tests. It's partly convention, but also writing rm -r hls4ml* to clean up after running locally makes me nervous 😅