Tippecanoe formatted every double it wrote through milo::dtoa_milo, a
vendored Grisu2. Grisu2 is fast, but it guarantees neither the shortest
digit string nor the correctly rounded one: it only guarantees that what
it prints parses back to the value it came from. In practice it prints a
digit more than necessary about 0.16% of the time, and picks a neighbor
of the correctly rounded digits about 32% of the time.
This ports Russ Cox's fpfmt (https://github.com/rsc/fpfmt) to C++ in
fpfmt/ and formats through it instead. fpfmt is both shortest and
correctly rounded, and it is faster:
full std::string formatting Grisu2 fpfmt speedup
random bit patterns 156.62 ns 66.83 ns 2.34x
geo coordinates 124.07 ns 58.62 ns 2.12x
short decimals 69.37 ns 49.16 ns 1.41x
small integers 44.18 ns 38.06 ns 1.16x
digit generation only Grisu2 fpfmt speedup
random bit patterns 90.07 ns 20.81 ns 4.33x
geo coordinates 80.64 ns 20.18 ns 4.00x
short decimals 55.61 ns 21.90 ns 2.54x
small integers 40.23 ns 22.50 ns 1.79x
(Intel Xeon @ 2.80GHz, g++ 13.3 -O3. `make fpfmt-bench` reproduces this,
and `./fpfmt-bench -check` reruns the correctness sweep, which is why
milo/dtoa_milo.h is kept even though nothing links it any more.)
The port is deliberately literal, so it can be diffed against fpfmt.go.
Its Short() agrees bit for bit with the Go original's on 445,640 values
covering powers of ten, small integers and reciprocals, subnormals, and
random bit patterns. Over 38.5 million values, fpfmt::dtoa always round
trips, is never longer than Grisu2's output, and is shorter 61,329 times.
Output is otherwise formatted exactly as before, including the choice
between plain and exponential notation, so 26 expected test outputs
change: some numbers lose digits (-26.170044999999999 becomes
-26.170045), and some have a corrected final digit (9.823748927348929e+55
becomes 9.823748927348928e+55). Every changed token was checked to parse
back to the identical double; none of the values themselves moved.
milo/milo.h, whose only job was to declare the C shim jsonpull calls, is
replaced by fpfmt/fpfmt.h, and the shim is renamed dtoa_shortest.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014wJRAuhMninQE4wK2TUfuZ
* Add a flag to use an H3 index for the feature index
* Give mvt_value and serial_val a double-with-count concept
* Switch mean over to internal accumulation state
* Get rid of the attribute accumulation map
* Change vectors of features to vectors of pointers to features
* Fix --coalesce
* Revert "Add a flag to use an H3 index for the feature index"
This reverts commit b9b48f42c9.
* Update version and changelog
* Add an option to retain N times as many points as usual at each zoom
* Tests for point multipler with specified and guessed maxzooms
* Work in progress on inverse spatial ordering
* Fix inverse spatial feature order
* --reorder was depending on a feature index that wasn't being preserved
* Separate ordering by feature_minzoom from ordering inverse-spatially
* Add a test for the inverse spatial ordering
* Store the basezoom/droprate/multiplier decisions in tileset metadata
* Progress on adding filters to tippecanoe-overzoom
* Type promotion for comparison
* Look up the attribute value for ordering
* Add test of thinning and ordering features
* Plumb tippecanoe_decisions metadata through pmtiles
* Be careful not to put infinities in JSON
* Fix accidental dropping in what is meant to preserve sparse points
* Start distinguishing true, false, and null in expressions
* Most of the type conversions
* Add boolean conversions
* Literals and conjunctions
* Add filtering to tippecanoe-overzoom
* Add a test of filtering in overzoom
* Fix boolean conjunctions
* Handle the combination of cluster size and filtering
* Rework dot dropping to reconcile density threshold and multiplier
* Revert "Rework dot dropping to reconcile density threshold and multiplier"
This reverts commit f253a66382.
* Retain points by multiplier within each tile, not in global probability
* Test that intends to verify that the multiplier is reversible
* Get the test to detect the discrepancy
* Mark the start of multiplier clusters with a magic attribute
* Add string-contains
* Add in and ni operators
* Revert "Look up the attribute value for ordering"
This reverts commit 56bc73e49a.
* Revert "Type promotion for comparison"
This reverts commit 6f3256f5af.
* Make number formatting in tippecanoe_decisions consistent
* Revert "Add a test for the inverse spatial ordering"
This reverts commit c8047de9ab.
* Revert "Separate ordering by feature_minzoom from ordering inverse-spatially"
This reverts commit 35b19a223c.
* Revert "Fix inverse spatial feature order"
This reverts commit 5978ecdb44.
* Revert "Work in progress on inverse spatial ordering"
This reverts commit fdf230f632.
* Somehow missed the tests associated with that last revert
* Round-robin assign attributes to partials from across the multiplier
* Count the multiplier separately in each layer
* Fix distribution of accumulated attribute across multiplier features
* Update changelog, version, and docs
* Add "is null" and "isnt null" expressions
* Update interpretation of FSL expressions to pass the tests
* Test to assert that polygons are unaffected by the multiplier
* Clean up and comment
* Remove accidental unused case
* Put all of this back in geometry.cpp for conflict resolution
* Stabilize line simplification to behave the same regardless of winding
* Round instead of truncating when clipping lines
* Restore non-Wagyu polygon clipping from prior to 2fdec7d2
* Make it round, not truncate, which reverts the last commit's test diffs
* Clip in floating point, not integers, which makes no difference
* Track nodes added at tile edges during clipping
* Scale geometry up before wagyu to prevent changes from precision loss
* Actually do the shared edge detection
* Fix cases where nodes were not being added at the tile boundary
* One more place I should have rounded
* Narrow down where the discrepancy comes in
* Revert "Narrow down where the discrepancy comes in"
This reverts commit 221c4c5fc0ac9a6567e091c6a94b3d87dc8ade83.
* Another attempt to narrow it down
* The discrepancy seems to be introduced in reordering. No obvious bug
* Was still truncating instead of rounding in projection
* Also makes no difference...
* Just forget that line reversal exists for a minute
* Just reversal no coalescing
* Try clipping in integers instead of floating point
* Don't simplify after coalescing if they said no simplification
* Check whether behavior is consistent with intentional simplification
* Replace more floating point with integer
* Are these three features enough to demonstrate the problem?
* Add a few more nearby borders
* All the features that touch tile 6/16/23
* Stay in integers in line simplification
* More attempts to solve failures to simplify consistently
* Fix most of the overflow errors
* Fix known cases of integer overflow
* All the tests change again
* Pull clipping and scaling code back out into clip.cpp
* Resolve the test conflicts
* Stabilize choice of which three points to keep with different windings
* Almost right, I think!
* Fix collapse of islands to shards
* Self-intersections in the same feature don't count
* Revert "Self-intersections in the same feature don't count"
This reverts commit e04b19916e.
* Don't scale down geometry if we are going to look for shared nodes
* Fix the missing multiply that was keeping simplification from happening
* Fix one more opportunity for overflow
* Somehow I deleted this test?
* Lost this test too
* Clean up debugging printfs
* Restore code sequence from main to make it reviewable
* Remove unneeded rounding
* Update documentation
* This test is no longer useful
* Back to floating point Douglas-Peucker to fix undersimplification
* Try an older ubuntu
* Revert "Try an older ubuntu"
This reverts commit 13fefacfd7.
* Log OS info
* Remove tests that are no longer needed
* Oops, did need that one after all
* Fix the arm vs x86 discrepancy?
* Try another quantization
* Cleanup from review
* Add a test for the actual purpose of this PR
* Starting on --set-attributes
* Add a JSON form to accumulate-attribute
* Fix formatting
* Set attributes, JSON form
* Also handle setting attributes to unquoted values
* Factoring out character-mangling in the names of tests
* Rename tests for new quoting convention
* Test for JSON form of attribute setting
* Test for JSON form of attribute accumulation
* Forgot to increment the version
* Calculate a new antimeridian-adjusted bounding box
* Add antimeridian bounding box to pmtiles, dirtiles, and tile-join
* Don't take out-of-bounds latitudes into account in the adjusted bbox
* Update changelog
* Forgot to adjust tests after the last change
* Round coordinates instead of truncating them
* Update all the tests for coordinate rounding changes
* Curses, integer division still truncates
* Fix tests
* Also round instead of shifting when looking for no-op linetos
* Should I worry that the same change for moveto doesn't change any tests?
* Also round instead of shifting when scaling down to maxzoom resolution
* Replace another explicit shift, for origin point
* Round instead of shift when writing clipped geometries to the next zoom
* Fix low-zoom gridding and smaller-than-a-pixel checks
* Don't guess an excessively large maxzoom when there is only one feature
* Add a test for guessing the maxzoom of a single point
* Explicitly sort by index if no other order distinguishes features
* Another affected test
* add pmtiles.hpp from github.com/protomaps/PMTiles [#10]
* tippecanoe main writes pmtiles output. [#10]
* detect output format using suffix
* after mbtiles is done writing, replace with pmtiles based on map/image tables.
* add method to write_json for writing json sub-object.
* tippecanoe-decode reads pmtiles input. [#10]
* tile-join reads and writes pmtiles. [#10]
* pmtiles test suite for decode and tile-join [#10]
* add base GitHub CI action for compiling and test suite.
* update pmtiles.hpp with z>15 fix
* Fix some ordering problems with pmtiles decode
* Pmtiles should also pass the raw tiles tests
* Eradicate spaces from tileset metadata JSON fields
* Eradicate spaces from more test fixtures
* Update more tests
* Pmtiles tests pass now too
* Remove unnecessary sort (and make indent)
* Update changelog
* The allow-existing test for pmtiles needs -o, not -e
* Declare --allow-existing to be unsupported for pmtiles.
It was always a bad idea even for mbtiles.
Co-authored-by: Brandon Liu <bdon@bdon.org>
* Handle points too when dropping or coalescing the "smallest" features.
* Add statistics of tile size reduction strategies to tileset metadata
* Update changelog and version
* Update documentation
Claude