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

88 lines
2.4 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 ceil"
}
fn signature(&self) -> Signature {
Signature::build("math ceil")
.input_output_types(vec![(Type::Number, Type::Int)])
.vectorizes_over_list(true)
.category(Category::Math)
}
fn usage(&self) -> &str {
"Returns the ceil of a number (smallest integer greater than or equal to that number)."
}
fn search_terms(&self) -> Vec<&str> {
vec!["ceiling", "round up", "rounding", "integer"]
}
fn run(
&self,
engine_state: &EngineState,
_stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let head = call.head;
// 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),
engine_state.ctrlc.clone(),
)
}
fn examples(&self) -> Vec<Example> {
vec![Example {
description: "Apply the ceil function to a list of numbers",
example: "[1.5 2.3 -3.1] | math ceil",
result: Some(Value::List {
vals: vec![Value::test_int(2), Value::test_int(3), Value::test_int(-3)],
span: Span::test_data(),
}),
}]
}
}
fn operate(value: Value, head: Span) -> Value {
match value {
Value::Int { .. } => value,
Value::Float { val, span } => Value::Int {
val: val.ceil() as i64,
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 {})
}
}