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Keep order for par-each (#10249)
# Description
This PR adds new flag `--keep-order/-k` for the `par_each` filter. This
flag keeps sequence of output same as the order of input.
Output without the flag:
```nu
> 1..6 | par-each {|n| $n * 2 }
╭────╮
│ 4 │
│ 10 │
│ 2 │
│ 8 │
│ 12 │
│ 6 │
╰────╯
```
Output with the `--keep-order` flag:
```nu
> 1..6 | par-each --keep-order {|n| $n * 2 }
╭────╮
│ 2 │
│ 4 │
│ 6 │
│ 8 │
│ 10 │
│ 12 │
╰────╯
```
I think the presence of this flag is justified, since:
- Much easier to use than `.. | enumerate | par-each {|p| update item
..} | sort-by index | get item`
- Faster, as it uses internally parallel sorting in the same thread pool
A note about naming: it may conflict with `--keep-empty/-k` flag of the
`each` filter if the same feature will be used in `par-each`, so maybe
it needs some other name.
This commit is contained in:
Nano
GitHub
parent
eddff46155
commit
7b89fab327
@ -37,6 +37,11 @@ impl Command for ParEach {
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"the number of threads to use",
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Some('t'),
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)
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.switch(
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"keep-order",
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"keep sequence of output same as the order of input",
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Some('k'),
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)
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.required(
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"closure",
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SyntaxShape::Closure(Some(vec![SyntaxShape::Any, SyntaxShape::Int])),
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@ -49,39 +54,43 @@ impl Command for ParEach {
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fn examples(&self) -> Vec<Example> {
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vec![
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Example {
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example: "[1 2 3] | par-each {|| 2 * $in }",
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example: "[1 2 3] | par-each {|e| $e * 2 }",
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description:
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"Multiplies each number. Note that the list will become arbitrarily disordered.",
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result: None,
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},
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Example {
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example: r#"[foo bar baz] | par-each {|e| $e + '!' } | sort"#,
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description: "Output can still be sorted afterward",
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result: Some(Value::list(
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vec![
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Value::test_string("bar!"),
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Value::test_string("baz!"),
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Value::test_string("foo!"),
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],
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Span::test_data(),
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)),
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example: r#"[1 2 3] | par-each --keep-order {|e| $e * 2 }"#,
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description: "Multiplies each number, keeping an original order",
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result: Some(Value::test_list(vec![
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Value::test_int(2),
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Value::test_int(4),
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Value::test_int(6),
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])),
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},
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Example {
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example: r#"1..3 | enumerate | par-each {|p| update item ($p.item * 2)} | sort-by item | get item"#,
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description: "Enumerate and sort-by can be used to reconstruct the original order",
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result: Some(Value::list(
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vec![Value::test_int(2), Value::test_int(4), Value::test_int(6)],
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Span::test_data(),
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)),
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result: Some(Value::test_list(vec![
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Value::test_int(2),
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Value::test_int(4),
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Value::test_int(6),
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])),
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},
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Example {
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example: r#"[foo bar baz] | par-each {|e| $e + '!' } | sort"#,
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description: "Output can still be sorted afterward",
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result: Some(Value::test_list(vec![
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Value::test_string("bar!"),
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Value::test_string("baz!"),
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Value::test_string("foo!"),
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])),
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},
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Example {
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example: r#"[1 2 3] | enumerate | par-each { |e| if $e.item == 2 { $"found 2 at ($e.index)!"} }"#,
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description:
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"Iterate over each element, producing a list showing indexes of any 2s",
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result: Some(Value::list(
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vec![Value::test_string("found 2 at 1!")],
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Span::test_data(),
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)),
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result: Some(Value::test_list(vec![Value::test_string("found 2 at 1!")])),
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},
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]
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}
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@ -114,6 +123,7 @@ impl Command for ParEach {
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let capture_block: Closure = call.req(engine_state, stack, 0)?;
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let threads: Option<usize> = call.get_flag(engine_state, stack, "threads")?;
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let max_threads = threads.unwrap_or(0);
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let keep_order = call.has_flag("keep-order");
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let metadata = input.metadata();
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let ctrlc = engine_state.ctrlc.clone();
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let outer_ctrlc = engine_state.ctrlc.clone();
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@ -123,14 +133,27 @@ impl Command for ParEach {
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let redirect_stdout = call.redirect_stdout;
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let redirect_stderr = call.redirect_stderr;
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// A helper function sorts the output if needed
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let apply_order = |mut vec: Vec<(usize, Value)>| {
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if keep_order {
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// It runs inside the rayon's thread pool so parallel sorting can be used.
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// There are no identical indexes, so unstable sorting can be used.
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vec.par_sort_unstable_by_key(|(index, _)| *index);
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}
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vec.into_iter().map(|(_, val)| val)
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};
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match input {
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PipelineData::Empty => Ok(PipelineData::Empty),
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PipelineData::Value(Value::Range { val, .. }, ..) => Ok(create_pool(max_threads)?
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.install(|| {
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val.into_range_iter(ctrlc.clone())
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let vec = val
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.into_range_iter(ctrlc.clone())
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.expect("unable to create a range iterator")
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.enumerate()
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.par_bridge()
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.map(move |x| {
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.map(move |(index, x)| {
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let block = engine_state.get_block(block_id);
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let mut stack = stack.clone();
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@ -144,7 +167,7 @@ impl Command for ParEach {
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let val_span = x.span();
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let x_is_error = x.is_error();
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match eval_block_with_early_return(
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let val = match eval_block_with_early_return(
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engine_state,
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&mut stack,
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block,
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@ -153,21 +176,24 @@ impl Command for ParEach {
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redirect_stderr,
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) {
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Ok(v) => v.into_value(span),
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Err(error) => Value::error(
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chain_error_with_input(error, x_is_error, val_span),
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val_span,
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),
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}
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};
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(index, val)
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})
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.collect::<Vec<_>>()
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.into_iter()
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.into_pipeline_data(ctrlc)
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.collect::<Vec<_>>();
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apply_order(vec).into_pipeline_data(ctrlc)
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})),
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PipelineData::Value(Value::List { vals: val, .. }, ..) => Ok(create_pool(max_threads)?
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.install(|| {
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val.par_iter()
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.map(move |x| {
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let vec = val
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.par_iter()
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.enumerate()
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.map(move |(index, x)| {
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let block = engine_state.get_block(block_id);
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let mut stack = stack.clone();
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@ -181,7 +207,7 @@ impl Command for ParEach {
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let val_span = x.span();
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let x_is_error = x.is_error();
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match eval_block_with_early_return(
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let val = match eval_block_with_early_return(
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engine_state,
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&mut stack,
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block,
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@ -194,16 +220,19 @@ impl Command for ParEach {
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chain_error_with_input(error, x_is_error, val_span),
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val_span,
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),
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}
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};
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(index, val)
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})
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.collect::<Vec<_>>()
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.into_iter()
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.into_pipeline_data(ctrlc)
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.collect::<Vec<_>>();
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apply_order(vec).into_pipeline_data(ctrlc)
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})),
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PipelineData::ListStream(stream, ..) => Ok(create_pool(max_threads)?.install(|| {
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stream
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let vec = stream
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.enumerate()
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.par_bridge()
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.map(move |x| {
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.map(move |(index, x)| {
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let block = engine_state.get_block(block_id);
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let mut stack = stack.clone();
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@ -217,7 +246,7 @@ impl Command for ParEach {
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let val_span = x.span();
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let x_is_error = x.is_error();
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match eval_block_with_early_return(
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let val = match eval_block_with_early_return(
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engine_state,
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&mut stack,
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block,
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@ -230,23 +259,26 @@ impl Command for ParEach {
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chain_error_with_input(error, x_is_error, val_span),
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val_span,
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),
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}
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};
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(index, val)
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})
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.collect::<Vec<_>>()
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.into_iter()
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.into_pipeline_data(ctrlc)
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.collect::<Vec<_>>();
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apply_order(vec).into_pipeline_data(ctrlc)
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})),
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PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
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PipelineData::ExternalStream {
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stdout: Some(stream),
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..
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} => Ok(create_pool(max_threads)?.install(|| {
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stream
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let vec = stream
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.enumerate()
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.par_bridge()
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.map(move |x| {
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.map(move |(index, x)| {
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let x = match x {
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Ok(x) => x,
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Err(err) => return Value::error(err, span),
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Err(err) => return (index, Value::error(err, span)),
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};
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let block = engine_state.get_block(block_id);
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@ -259,7 +291,7 @@ impl Command for ParEach {
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}
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}
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match eval_block_with_early_return(
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let val = match eval_block_with_early_return(
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engine_state,
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&mut stack,
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block,
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@ -269,11 +301,13 @@ impl Command for ParEach {
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) {
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Ok(v) => v.into_value(span),
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Err(error) => Value::error(error, span),
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}
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};
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(index, val)
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})
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.collect::<Vec<_>>()
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.into_iter()
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.into_pipeline_data(ctrlc)
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.collect::<Vec<_>>();
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apply_order(vec).into_pipeline_data(ctrlc)
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})),
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// This match allows non-iterables to be accepted,
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// which is currently considered undesirable (Nov 2022).
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