filterbench

This is a primitive benchmark for the note filters in LMMS. The test is basically filtering 100 seconds of 96k stereo sound, and the reported units/second reflects how many of these units the filter handles in a second.

1. Edit bench.shto select filters to benchmark and set optimization options
2. Run bench.sh --compile to generate the following binaries in directory tests:

• baseline is the original, with standard LMMS compilation options
• optimized is the original filter code, optimized
• modified is the modified filter code (in basic_filters_modified.h), optimized

3. Run bench.sh --check to verify the results are identical between original and modified code (NB Harder optimizations, like --fast-math seem to sometimes create small differences even in untouched parts of the code, somewhere around the fifth decimal or so)
4. Run bench.sh --run [N] to test the selected filters. The optional numeric argument N selects the number of iterations.