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
* Progress on plumbing a string pool for full_keys through
* More plumbing for key_pool
* Don't keep features with identical locations as multiplier features
* Revert "Don't keep features with identical locations as multiplier features"
This reverts commit 413f0c8024.
* Adjust calculated maxzoom to account for duplicate feature locations
* Update changelog and version
* Add a test affected by the maxzoom change with duplicate locations
* Round the drop rate a little for cross-platform test consistency
* Add an all-mvt_value attribute accumulation path
* Only bin by ID, not geometrically
* A little cleanup; changelog and version; test
* Remove accidental double-conversion
* Replace duplicated code with template
* Update changelog
* Plumb bounding boxes through potential intersections
* Quick bbox reject for bins that can't possibly intersect
* Inching toward attribute accumulation in megatile handling
* Some sort of test for how all these things interact with each other.
Automatic numeric attribute accumulation does *not* apply to attributes
that have an explicit attribute accumulator set, because the order of
operations is too messy and weird
* More sketching
* More sketching
* Actually do some accumulation
* Put all that behind an --accumulate-numeric flag
* Use the same attribute accumulation logic in binning as in megatiles
* Fix backwards conditional
* Add means, but somehow I have some counts of 0
* Handle aggregated attributes with no base attribute in the feature
* Checkpoint before I break everything
* Found a flaw, now to debug
* Fix a typo that broke accumulation
* Add binning tests
* Make sure IDs make it through on the bins
* Fix count/mean accumulation
* Make the numeric accumulation prefix configurable
* Make sure the accumulate test still works with a different prefix
* Forgot to update this test
* More testing to make sure cluster sizes make it all the way through
* Fix neglected --accumulate-attribute when binning
* Mark unexercised attribute accumulation cases as "can't happen"
* Factor out numeric preservation
* Attrs with the accumulation prefix are just preserved, not accumulated
* Test behavior of prefixed attributes
* Plumbing for exclude and exclude-prefix
* Implement and test attribute prefix stripping in overzoom
* Update version and changelog
* For debugging, make an attribute list of source feature IDs
* Revert "For debugging, make an attribute list of source feature IDs"
This reverts commit 65fc99c9d1.
* Factoring out tilestats management from GeoJSON file reading
* Move code around so overzoom can link against parse_layers
* Read the file of bins
* Plumb the bins through to overzoom()
* Some zip code bins to test with
* (Currently non-functional) test of binning
* Starting to spell out the bin matching loop
* Can't flatten points, so don't flatten bins either
* More fleshing out bin traversal
* Bounding box of tile-relative mvt geometry
* Smallest enclosing tile from bbox
* Most of the bin scan
* Add point in polygon check. It crashes.
* Find the matching bins
* GDAL-style bounding boxes have eaten my brain
* Make some features to bin into
* Increment a count as features are found to be within the bins
* Fix longitude wraparound in overzoom bins
* Fix the tests
* Push off attribute copying until after bin assignment
* Carry sum of numeric attributes into the bins
* Also add mean, min, and max
* Add --calculate-feature-index since I keep needing it for testing
* Add an option to accumulate sum/mean/max/min/count of all numeric attrs
* Don't bake in tippecanoe:mean, since we redo it from sum and count
* Forgot to update this test fixture after removing tiled mean
* Update version and changelog
* Add a way to run tippecanoe single-threaded for profiling
* Do less work when the tilestats sample values list is already full
* Save a copy when retrieving the attribute key
* Fewer atomic operations
* Move string hashing from mbtiles to text
* Only do approximate attribute deduplication when writing tiles
* Feature dropping tests are sensitive to exact tile size
* All tile creators now create a string pool for the tile
* Features clipped away to nothing should not participate in that tile
* Revert "Only do approximate attribute deduplication when writing tiles"
This reverts commit c42b34b498.
* Also revert the related test changes
* Revert "Revert "Only do approximate attribute deduplication when writing tiles""
This reverts commit 18509876c3.
* Be more specific about the string hash function
* Use fnv1a instead of std::hash for everything
* Reduce the chance of hash collisions
* Stick a hash search on the front of the tree search in addpool
* Eliminate repeated hashing of the same string
* Switch instead of ifs in json parsing
* A few more cases to populate the hash in addpool
* Store the hash in the tree instead of recalculating
* Add explanatory comment for mysterious argument
* Fewer copies in attribute stringification
* Clean up ancient weirdness in JSON attribute stringification
* More serial_val cleanup
* Pass a serial_feature to rewrite instead of many broken-down arguments
* Get rid of the multiple geometries within `partial`
* Revert "Pass a serial_feature to rewrite instead of many broken-down arguments"
This reverts commit 6f4ab9b725.
* Goodbye, struct coalesce
* Revert "Features clipped away to nothing should not participate in that tile"
This reverts commit 124462fbdc.
* Migrating fields from partial to serial_feature
* Name reconciliation between serial_feature and partial
* Replace struct partial with an augmented serial_feature
* Fix some overzealous search-and-replace renaming
* Don't say struct so often
* Remove more of the former partial construction
* Commenting and cleaning up
* Trying again to avoid all these arguments to rewrite
* I swear I did this same thing before and it didn't work.
* More rewrite cleanup
* Exile --detect-shared-borders to its own file
* Add missing headers
* More commenting and cleanup
* More comments
* Sprinkle consts around
* Emplacing and std::moving
* More cleanup
* That shouldn't have worked after a std::move
* Don't need to allocate memory to compare keys
* Reduce use of the global string pool in tiling
* Another avoidable mvt_value construction
* Further reduction to explicit string pool passing
* These reverses are no longer optimizations
* These layernames can all be references
* Don't drag an unused layername string around with every feature
* Heed a compiler warning about potential buffer overflow
* Fix my confusion about which feature's string pool is relevant
* Avoid some unnecessary allocations in attribute accumulation
* Maybe faster serialization?
* Eliminate a comparison
* Do the same here
* Save a couple of allocations when parsing numbers in JSON
* Immediately assign features to layers instead of subdividing later
* Maintain tilestats for tippecanoe:retain_points_multiplier_sequence
* Crunch out more duplicate attribute values when writing out the tile
* Do tilestats for tippecanoe:retain_points_multiplier_first too
* Shell filters need to be real threads, even if nothing else does
* Simplify tippecanoe_minzoom/maxzoom representation
* Update version and changelog
* Speed up mvt_value comparison
* Converting repetitive ifs to cases
* More conversions from ifs to cases
* Optimize the always-true filter case
* Don't convert types of attributes without accumulators
* Unordered map seems to be faster than map
* Add missing header
* Fix some warnings
* Fix the warnings better
* Avoid an int->string->int conversion
* Lazily initialize layer key and values maps when actually needed
* More switches from maps to unordered_maps
* Sure, I'll take the microoptimization
* More emplacement
* Save some copies
* Emplaces and moves
* Lazy linear scan of attributes instead of building a map
* Extra printfs, missing header
* Avoid clipping if the input and output tiles are the same
* But do clip if the tile extent is being reduced
* Make sure I'm not constructing std::strings here at runtime
* More worrying about runtime string construction
* A couple more std::moves
* Const references!
* More const references
* Another std::move
* Make the string_value of mvt_value std::optional
* Reserve storage when decoding
* Provision for different mvt_values to share a string pool
* Use the string pool when decoding
* Avoid another string construction
* Try limiting the depth of the search for duplicate attributes
* Revert "Try limiting the depth of the search for duplicate attributes"
This reverts commit 9ec94a15ff.
* Update changelog
* Fix typo noticed during code review
* Starting to factor out attribute accumulation into its own file
* Continuing to factor out attribute accumulation
* Reduce duplicate code
* Plumbing the accumulate-attribute option around
* Call the attribute accumulator
* Test that accumulation works
* Add missing #includes
* Don't sort within individual multiplier clusters
Doing so throws off the spatial distribution of the low zooms
* Docs and changelog
* Add comments
Claude