The transmute was unsound.
There are many instances of .unwrap_or('\x00') for "ignoring" EOF which
either do not make the situation worse than it was (well, actually make
it better, since it's easy to grep for places that don't handle EOF) or
can never ever be read.
Fixes#8971.
This also drops support for the managed pointer POISON_ON_FREE feature
as it's not worth adding back the support for it. After a snapshot, the
leftovers can be removed.
This pull request:
1) Changes the initial insertion sort to be in-place, and defers allocation of working set until merge is needed.
2) Increases the increases the maximum run length to use insertion sort for from 8 to 32 elements. This increases the size of vectors that will not allocate, and reduces the number of merge passes by two. It seemed to be the sweet spot in the benchmarks that I ran.
Here are the results of some benchmarks. Note that they are sorting u64s, so types that are more expensive to compare or copy may have different behaviors.
Before changes:
```
test vec::bench::sort_random_large bench: 719753 ns/iter (+/- 130173) = 111 MB/s
test vec::bench::sort_random_medium bench: 4726 ns/iter (+/- 742) = 169 MB/s
test vec::bench::sort_random_small bench: 344 ns/iter (+/- 76) = 116 MB/s
test vec::bench::sort_sorted bench: 437244 ns/iter (+/- 70043) = 182 MB/s
```
Deferred allocation (8 element insertion sort):
```
test vec::bench::sort_random_large bench: 702630 ns/iter (+/- 88158) = 113 MB/s
test vec::bench::sort_random_medium bench: 4529 ns/iter (+/- 497) = 176 MB/s
test vec::bench::sort_random_small bench: 185 ns/iter (+/- 49) = 216 MB/s
test vec::bench::sort_sorted bench: 425853 ns/iter (+/- 60907) = 187 MB/s
```
Deferred allocation (16 element insertion sort):
```
test vec::bench::sort_random_large bench: 692783 ns/iter (+/- 165837) = 115 MB/s
test vec::bench::sort_random_medium bench: 4434 ns/iter (+/- 722) = 180 MB/s
test vec::bench::sort_random_small bench: 187 ns/iter (+/- 38) = 213 MB/s
test vec::bench::sort_sorted bench: 393783 ns/iter (+/- 85548) = 203 MB/s
```
Deferred allocation (32 element insertion sort):
```
test vec::bench::sort_random_large bench: 682556 ns/iter (+/- 131008) = 117 MB/s
test vec::bench::sort_random_medium bench: 4370 ns/iter (+/- 1369) = 183 MB/s
test vec::bench::sort_random_small bench: 179 ns/iter (+/- 32) = 223 MB/s
test vec::bench::sort_sorted bench: 358353 ns/iter (+/- 65423) = 223 MB/s
```
Deferred allocation (64 element insertion sort):
```
test vec::bench::sort_random_large bench: 712040 ns/iter (+/- 132454) = 112 MB/s
test vec::bench::sort_random_medium bench: 4425 ns/iter (+/- 784) = 180 MB/s
test vec::bench::sort_random_small bench: 179 ns/iter (+/- 81) = 223 MB/s
test vec::bench::sort_sorted bench: 317812 ns/iter (+/- 62675) = 251 MB/s
```
This is the best I could manage with the basic merge sort while keeping the invariant that the original vector must contain each element exactly once when the comparison function is called. If one is not married to a stable sort, an in-place n*log(n) sorting algorithm may have better performance in some cases.
for #12011
cc @huonw
Added a seperate in-place insertion sort for short vectors.
Increased threshold for insertion short for 8 to 32 elements
for small types and 16 for larger types. Added benchmarks
for sorting larger types.
This PR extends the tidy formatting check to rust files in the test folder. To facilitate this, a few flags were added to tidy:
* `xfail-tidy-cr` - Disables the check for CR characters for all following lines in the file
* `xfail-tidy-tab` - Disables the check for tab characters for all following lines in the file
* `xfail-tidy-linelength` - Disables the line length check for all following lines in the file
Checks should not have to be disabled often. I disabled line length checks in `debug-info` tests that use `debugger:` checks, but aside from that, there were relatively few exclusions. Running tidy on all the tests does slow down the formatting check, so it may be worth investigating further optimization.
cc #4534
`from_utf8_lossy()` takes a byte vector and produces a `~str`, converting
any invalid UTF-8 sequence into the U+FFFD REPLACEMENT CHARACTER.
The replacement follows the guidelines in §5.22 Best Practice for U+FFFD
Substitution from the Unicode Standard (Version 6.2)[1], which also
matches the WHATWG rules for utf-8 decoding[2].
[1]: http://www.unicode.org/versions/Unicode6.2.0/ch05.pdf
[2]: http://encoding.spec.whatwg.org/#utf-8Closes#9516.
Part of #8784
Changes:
- Everything labeled under collections in libextra has been moved into a new crate 'libcollection'.
- Renamed container.rs to deque.rs, since it was no longer 'container traits for extra', just a deque trait.
- Crates that depend on the collections have been updated and dependencies sorted.
- I think I changed all the imports in the tests to make sure it works. I'm not entirely sure, as near the end of the tests there was yet another `use` that I forgot to change, and when I went to try again, it started rebuilding everything, which I don't currently have time for.
There will probably be incompatibility between this and the other pull requests that are splitting up libextra. I'm happy to rebase once those have been merged.
The tests I didn't get to run should pass. But I can redo them another time if they don't.
from_utf8_lossy() takes a byte vector and produces a ~str, converting
any invalid UTF-8 sequence into the U+FFFD REPLACEMENT CHARACTER.
The replacement follows the guidelines in §5.22 Best Practice for U+FFFD
Substitution from the Unicode Standard (Version 6.2)[1], which also
matches the WHATWG rules for utf-8 decoding[2].
[1]: http://www.unicode.org/versions/Unicode6.2.0/ch05.pdf
[2]: http://encoding.spec.whatwg.org/#utf-8
This has been a long time coming. Conditions in rust were initially envisioned
as being a good alternative to error code return pattern. The idea is that all
errors are fatal-by-default, and you can opt-in to handling the error by
registering an error handler.
While sounding nice, conditions ended up having some unforseen shortcomings:
* Actually handling an error has some very awkward syntax:
let mut result = None;
let mut answer = None;
io::io_error::cond.trap(|e| { result = Some(e) }).inside(|| {
answer = Some(some_io_operation());
});
match result {
Some(err) => { /* hit an I/O error */ }
None => {
let answer = answer.unwrap();
/* deal with the result of I/O */
}
}
This pattern can certainly use functions like io::result, but at its core
actually handling conditions is fairly difficult
* The "zero value" of a function is often confusing. One of the main ideas
behind using conditions was to change the signature of I/O functions. Instead
of read_be_u32() returning a result, it returned a u32. Errors were notified
via a condition, and if you caught the condition you understood that the "zero
value" returned is actually a garbage value. These zero values are often
difficult to understand, however.
One case of this is the read_bytes() function. The function takes an integer
length of the amount of bytes to read, and returns an array of that size. The
array may actually be shorter, however, if an error occurred.
Another case is fs::stat(). The theoretical "zero value" is a blank stat
struct, but it's a little awkward to create and return a zero'd out stat
struct on a call to stat().
In general, the return value of functions that can raise error are much more
natural when using a Result as opposed to an always-usable zero-value.
* Conditions impose a necessary runtime requirement on *all* I/O. In theory I/O
is as simple as calling read() and write(), but using conditions imposed the
restriction that a rust local task was required if you wanted to catch errors
with I/O. While certainly an surmountable difficulty, this was always a bit of
a thorn in the side of conditions.
* Functions raising conditions are not always clear that they are raising
conditions. This suffers a similar problem to exceptions where you don't
actually know whether a function raises a condition or not. The documentation
likely explains, but if someone retroactively adds a condition to a function
there's nothing forcing upstream users to acknowledge a new point of task
failure.
* Libaries using I/O are not guaranteed to correctly raise on conditions when an
error occurs. In developing various I/O libraries, it's much easier to just
return `None` from a read rather than raising an error. The silent contract of
"don't raise on EOF" was a little difficult to understand and threw a wrench
into the answer of the question "when do I raise a condition?"
Many of these difficulties can be overcome through documentation, examples, and
general practice. In the end, all of these difficulties added together ended up
being too overwhelming and improving various aspects didn't end up helping that
much.
A result-based I/O error handling strategy also has shortcomings, but the
cognitive burden is much smaller. The tooling necessary to make this strategy as
usable as conditions were is much smaller than the tooling necessary for
conditions.
Perhaps conditions may manifest themselves as a future entity, but for now
we're going to remove them from the standard library.
Closes#9795Closes#8968
This has been a long time coming. Conditions in rust were initially envisioned
as being a good alternative to error code return pattern. The idea is that all
errors are fatal-by-default, and you can opt-in to handling the error by
registering an error handler.
While sounding nice, conditions ended up having some unforseen shortcomings:
* Actually handling an error has some very awkward syntax:
let mut result = None;
let mut answer = None;
io::io_error::cond.trap(|e| { result = Some(e) }).inside(|| {
answer = Some(some_io_operation());
});
match result {
Some(err) => { /* hit an I/O error */ }
None => {
let answer = answer.unwrap();
/* deal with the result of I/O */
}
}
This pattern can certainly use functions like io::result, but at its core
actually handling conditions is fairly difficult
* The "zero value" of a function is often confusing. One of the main ideas
behind using conditions was to change the signature of I/O functions. Instead
of read_be_u32() returning a result, it returned a u32. Errors were notified
via a condition, and if you caught the condition you understood that the "zero
value" returned is actually a garbage value. These zero values are often
difficult to understand, however.
One case of this is the read_bytes() function. The function takes an integer
length of the amount of bytes to read, and returns an array of that size. The
array may actually be shorter, however, if an error occurred.
Another case is fs::stat(). The theoretical "zero value" is a blank stat
struct, but it's a little awkward to create and return a zero'd out stat
struct on a call to stat().
In general, the return value of functions that can raise error are much more
natural when using a Result as opposed to an always-usable zero-value.
* Conditions impose a necessary runtime requirement on *all* I/O. In theory I/O
is as simple as calling read() and write(), but using conditions imposed the
restriction that a rust local task was required if you wanted to catch errors
with I/O. While certainly an surmountable difficulty, this was always a bit of
a thorn in the side of conditions.
* Functions raising conditions are not always clear that they are raising
conditions. This suffers a similar problem to exceptions where you don't
actually know whether a function raises a condition or not. The documentation
likely explains, but if someone retroactively adds a condition to a function
there's nothing forcing upstream users to acknowledge a new point of task
failure.
* Libaries using I/O are not guaranteed to correctly raise on conditions when an
error occurs. In developing various I/O libraries, it's much easier to just
return `None` from a read rather than raising an error. The silent contract of
"don't raise on EOF" was a little difficult to understand and threw a wrench
into the answer of the question "when do I raise a condition?"
Many of these difficulties can be overcome through documentation, examples, and
general practice. In the end, all of these difficulties added together ended up
being too overwhelming and improving various aspects didn't end up helping that
much.
A result-based I/O error handling strategy also has shortcomings, but the
cognitive burden is much smaller. The tooling necessary to make this strategy as
usable as conditions were is much smaller than the tooling necessary for
conditions.
Perhaps conditions may manifest themselves as a future entity, but for now
we're going to remove them from the standard library.
Closes#9795Closes#8968
