Reviewers: , Message: (this still needs some work, but the speedup might be worth an early look)
Description: Rewrite Skyline code With this change, Carver MSDM goes from 38 seconds to 32 seconds, a 15% improvement. * Do not use contiguous buildings. Instead, Y=-infinity is represented by simply omitting the building. This reduces memory requirements (for example, an empty skyline needs no buildings at all.), and obviates the Skyline::normalize() call which takes ~1 % of CPU. * Buildings store Y coordinate of the left edge, rather than the intercept at x==0.0. This avoid excessive rounding problems when X is large, and lets us compute building.height_at(x[LEFT]) cheaply. * Avoid using infinity and NaN. We only let the X coordinates at the be infinite (which is only necessary if a minimum height is specified) * Aggressively prune zero width buildings. Adjust input/regression/skyline-point-extent to match this behavior * Simplify the merge code, using less nested if statements. * Add a unittest for the Skyline code * Debug output is produced with Lookup::segments_to_line_stencil() Please review this at https://codereview.appspot.com/547980044/ Affected files (+716, -421 lines): M input/regression/skyline-point-extent.ly A input/regression/unittests.ly M lily/axis-group-interface.cc M lily/include/lookup.hh M lily/include/skyline.hh M lily/lookup.cc M lily/separation-item.cc M lily/skyline.cc M lily/system.cc
