#5922 Rewrite Skyline code

[Han-Wen Nienhuys]

• 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()

https://codereview.appspot.com/547980044

[Anonymous]

Patch does not apply to current master.

[Han-Wen Nienhuys]

don't trim zero width buildings

https://codereview.appspot.com/547980044

[Han-Wen Nienhuys]

get rid of interval

https://codereview.appspot.com/547980044

[Anonymous]

Passes make, make check and a full make doc. Reg test diff attached.

[Han-Wen Nienhuys]

needs more benchmarking, but looks performance neutral .

[Anonymous]

Patch on countdown for April 30th

[Jonas Hahnfeld]

Hm, actually I had some comments yesterday that have not been addressed yet.

[Han-Wen Nienhuys]

I put this on "wait", no? This should not be merged as long as it's not
showing improved benchmarks

Op di 28 apr. 2020 09:43 schreef Jonas Hahnfeld hahnjo@users.sourceforge.net:

Hm, actually I had some comments yesterday that have not been addressed
yet.

---

• [issues:#5922] https://sourceforge.net/p/testlilyissues/issues/5922/
  Rewrite Skyline code*

Status: Started
Created: Sun Apr 19, 2020 09:42 PM UTC by Han-Wen Nienhuys
Last Updated: Tue Apr 28, 2020 07:33 AM UTC
Owner: Han-Wen Nienhuys

-

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()

https://codereview.appspot.com/547980044

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[Han-Wen Nienhuys]

setting to needs_work for now; this needs to be performance neutral at the very least.