nushell/crates/nu-command/src/math/arctan.rs
Stefan Holderbach a52386e837
Box ShellError in Value::Error (#8375)
# Description

Our `ShellError` at the moment has a `std::mem::size_of<ShellError>` of
136 bytes (on AMD64). As a result `Value` directly storing the struct
also required 136 bytes (thanks to alignment requirements).

This change stores the `Value::Error` `ShellError` on the heap.

Pro:
- Value now needs just 80 bytes
- Should be 1 cacheline less (still at least 2 cachelines)

Con:
- More small heap allocations when dealing with `Value::Error`
  - More heap fragmentation
  - Potential for additional required memcopies

# Further code changes

Includes a small refactor of `try` due to a type mismatch in its large
match.

# User-Facing Changes

None for regular users.

Plugin authors may have to update their matches on `Value` if they use
`nu-protocol`

Needs benchmarking to see if there is a benefit in real world workloads.
**Update** small improvements in runtime for workloads with high volume
of values. Significant reduction in maximum resident set size, when many
values are held in memory.

# Tests + Formatting
2023-03-12 09:57:27 +01:00

101 lines
2.9 KiB
Rust

use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Span, Type, Value};
#[derive(Clone)]
pub struct SubCommand;
impl Command for SubCommand {
fn name(&self) -> &str {
"math arctan"
}
fn signature(&self) -> Signature {
Signature::build("math arctan")
.switch("degrees", "Return degrees instead of radians", Some('d'))
.input_output_types(vec![(Type::Number, Type::Float)])
.vectorizes_over_list(true)
.category(Category::Math)
}
fn usage(&self) -> &str {
"Returns the arctangent of the number."
}
fn search_terms(&self) -> Vec<&str> {
vec!["trigonometry", "inverse"]
}
fn run(
&self,
engine_state: &EngineState,
_stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let head = call.head;
let use_degrees = call.has_flag("degrees");
// This doesn't match explicit nulls
if matches!(input, PipelineData::Empty) {
return Err(ShellError::PipelineEmpty { dst_span: head });
}
input.map(
move |value| operate(value, head, use_degrees),
engine_state.ctrlc.clone(),
)
}
fn examples(&self) -> Vec<Example> {
let pi = std::f64::consts::PI;
vec![
Example {
description: "Get the arctangent of 1",
example: "1 | math arctan",
result: Some(Value::test_float(pi / 4.0f64)),
},
Example {
description: "Get the arctangent of -1 in degrees",
example: "-1 | math arctan -d",
result: Some(Value::test_float(-45.0)),
},
]
}
}
fn operate(value: Value, head: Span, use_degrees: bool) -> Value {
match value {
numeric @ (Value::Int { .. } | Value::Float { .. }) => {
let (val, span) = match numeric {
Value::Int { val, span } => (val as f64, span),
Value::Float { val, span } => (val, span),
_ => unreachable!(),
};
let val = val.atan();
let val = if use_degrees { val.to_degrees() } else { val };
Value::Float { val, span }
}
Value::Error { .. } => value,
other => Value::Error {
error: Box::new(ShellError::OnlySupportsThisInputType {
exp_input_type: "numeric".into(),
wrong_type: other.get_type().to_string(),
dst_span: head,
src_span: other.expect_span(),
}),
},
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(SubCommand {})
}
}