This reverts commit 3370d58956.
This commit was done with an LLVM build that did not have assertions
enabled. There are LLVM assertions being triggered due to this commit.
Reopens#10627Reopens#12013Reopens#12027
There are still a few occurrences of "stage1" in the standard library
and self-hosted compiler source, however, these instances need a bit
more careful inspection to ensure no breakage.
The previous float-parsing method was lacking in a lot of areas. This
commit introduces a state-of-the art implementation that is both
accurate and fast to std.
Code is derived from working repo https://github.com/tiehuis/zig-parsefloat.
This includes more test-cases and performance numbers that are present
in this commit.
* Accuracy
The primary testing regime has been using test-data found at
https://github.com/tiehuis/parse-number-fxx-test-data. This is a fork of
upstream with support for f128 test-cases added. This data has been
verified against other independent implementations and represents
accurate round-to-even IEEE-754 floating point semantics.
* Performance
Compared to the existing parseFloat implementation there is ~5-10x
performance improvement using the above corpus. (f128 parsing excluded
in below measurements).
** Old
$ time ./test_all_fxx_data
3520298/5296694 succeeded (1776396 fail)
________________________________________________________
Executed in 28.68 secs fish external
usr time 28.48 secs 0.00 micros 28.48 secs
sys time 0.08 secs 694.00 micros 0.08 secs
** This Implementation
$ time ./test_all_fxx_data
5296693/5296694 succeeded (1 fail)
________________________________________________________
Executed in 4.54 secs fish external
usr time 4.37 secs 515.00 micros 4.37 secs
sys time 0.10 secs 171.00 micros 0.10 secs
Further performance numbers can be seen using the
https://github.com/tiehuis/simple_fastfloat_benchmark/ repository, which
compares against some other well-known string-to-float conversion
functions. A breakdown can be found here:
0d9f020f1a/PERFORMANCE.md (commit-b15406a0d2e18b50a4b62fceb5a6a3bb60ca5706)
In summary, we are within 20% of the C++ reference implementation and
have about ~600-700MB/s throughput on a Intel I5-6500 3.5Ghz.
* F128 Support
Finally, f128 is now completely supported with full accuracy. This does
use a slower path which is possible to improve in future.
* Behavioural Changes
There are a few behavioural changes to note.
- `parseHexFloat` is now redundant and these are now supported directly
in `parseFloat`.
- We implement round-to-even in all parsing routines. This is as
specified by IEEE-754. Previous code used different rounding
mechanisms (standard was round-to-zero, hex-parsing looked to use
round-up) so there may be subtle differences.
Closes#2207.
Fixes#11169.
We already have a LICENSE file that covers the Zig Standard Library. We
no longer need to remind everyone that the license is MIT in every single
file.
Previously this was introduced to clarify the situation for a fork of
Zig that made Zig's LICENSE file harder to find, and replaced it with
their own license that required annual payments to their company.
However that fork now appears to be dead. So there is no need to
reinforce the copyright notice in every single file.
* Add support for recursive objects to std.json.parse
* Remove previously defined error set
* Try with function which returns an error set
* Don't analyze already inferred types
* Add comptime to inferred_type parameter
* Make ParseInternalError to accept only a single argument
* Add public `ParseError` for `parse` function
* Use error.Foo syntax for errors instead of a named error set
* Better formatting
* Update to latest code changes
Comparisons with absolute epsilons are usually useful when comparing
numbers to zero, for non-zero numbers it's advised to switch to relative
epsilons instead to obtain meaningful results (check [1] for more
details).
The new API introduces approxEqAbs and approxEqRel, where the former
aliases and deprecated the old `approxEq`, allowing the user to pick the
right tool for the job.
The documentation is meant to guide the user in the choice of the
correct alternative.
[1] https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/
