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fix: Add Windows compatibility by replacing renameio with natefinch/atomic #12

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fix: Add Windows compatibility by replacing renameio with natefinch/atomic #12

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ff249e1
fix: Replace renameio with natefinch/atomic for Windows compatibility
soaringjerry Jun 29, 2025
badca06
Merge branch 'main' into fix-windows-compatibility
soaringjerry Jul 5, 2025
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21 changes: 10 additions & 11 deletions encode.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,14 @@ package hnsw

import (
"bufio"
"bytes"
"cmp"
"encoding/binary"
"fmt"
"io"
"os"

"github.com/google/renameio"
"github.com/natefinch/atomic"
)

// errorEncoder is a helper type to encode multiple values
Expand Down Expand Up @@ -301,14 +302,11 @@ func LoadSavedGraph[K cmp.Ordered](path string) (*SavedGraph[K], error) {

// Save writes the graph to the file.
func (g *SavedGraph[K]) Save() error {
tmp, err := renameio.TempFile("", g.Path)
if err != nil {
return err
}
defer tmp.Cleanup()

wr := bufio.NewWriter(tmp)
err = g.Export(wr)
// Create a buffer to write the data
var buf bytes.Buffer
wr := bufio.NewWriter(&buf)

err := g.Export(wr)
if err != nil {
return fmt.Errorf("exporting: %w", err)
}
Expand All @@ -318,9 +316,10 @@ func (g *SavedGraph[K]) Save() error {
return fmt.Errorf("flushing: %w", err)
}

err = tmp.CloseAtomicallyReplace()
// Use atomic.WriteFile to write the buffer contents atomically
err = atomic.WriteFile(g.Path, &buf)
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In order to maintain the performance characteristics of the previous approach (mainly, not buffering the whole structure in memory), we should g.export into a BufWriter that leads into an io.Pipe. We'd then pass the reader of that pipe into atomic.WriteFile. Then we only pay the (constant) memory cost of the BufWriter. The Pipe code is a bit annoying but the compat is worth it.

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Hi @ammario,

Thank you so much for taking the time to review this and for the excellent suggestion! That's a very insightful point about the potential memory overhead of buffering the entire graph before writing.

Your proposed solution using io.Pipe to create a streaming write is indeed a more elegant and memory-efficient approach in theory. I really appreciate you pointing this out.

I'm currently running some benchmarks to compare the performance characteristics and actual memory usage of two approaches:

The current implementation (buffering in memory).
Your suggested implementation (using io.Pipe).
I want to ensure the final solution is not only cross-platform palavras-chave but also as performant and memory-efficient as the original renameio implementation.

I will post my findings here shortly. Thanks again for the great feedback!

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The level of LLM in this contribution is nearly overwhelming

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@soaringjerry soaringjerry Jul 2, 2025 •
edited
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Hi @ammario,

I deeply leverage LLMs in my work to enhance both efficiency and quality. I'm experimenting with integrating my AI workflow approaches into projects (you can see Dreamhub and PCAS on my profile, though they're still in exploration phase), and these attempts have helped me achieve some nice productivity improvements.
I ran comprehensive benchmarks and found some interesting results:
For memory efficiency, the io.Pipe implementation performs excellently, achieving 50-65% memory savings across all test scales. Particularly with 50,000 nodes, it saves 128.2 MB of memory.
There's a clear performance trade-off: while single operations are 22-64% slower, surprisingly, io.Pipe actually performs 5.5% better in concurrent scenarios - likely due to reduced memory contention.
Based on this data, I believe both implementations have their place. For large-scale graph data or memory-constrained environments, io.Pipe's memory efficiency is worthwhile; for small datasets and latency-sensitive applications, the original Buffer implementation might be more suitable.

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This change should do one thing and do it well, which is adding Windows compatibility to the export function. I don't really care about the +/- 20%, there is an expectation (on consumers) that throughput could vary like that between versions. It's far more severe to double the peak memory usage, esp. when these structures are designed to get quite large.

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@ammario
I understand your perspective on memory usage. However, performance is critical for my use case - the 22-64% performance degradation would significantly impact my system's responsiveness.
I'll try to implement the io.Pipe approach for this PR when I have time, as I understand memory efficiency is your priority for the project. Meanwhile, I'll maintain the buffer-based implementation in my own fork since it better suits my performance requirements.
Thanks for the feedback.

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There may be a happy medium where both memory and throughput could be preserved. One concept is to use a bufio.Writer and bufio.Reader on both sides of the pipe. Since bufio.Reader implements WriteTo, io.Copy within atomic.WriteFile won't have to allocate a copy buf or do any memory shuffling. A lot of the new overhead with io.Pipe is due to synchronization which smart buffering should mostly alleviate.

if err != nil {
return fmt.Errorf("closing atomically: %w", err)
return fmt.Errorf("writing atomically: %w", err)
}

return nil
Expand Down
1 change: 1 addition & 0 deletions go.mod
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Expand Up @@ -8,6 +8,7 @@ require github.com/google/renameio v1.0.1

require (
github.com/chewxy/math32 v1.10.1 // indirect
github.com/natefinch/atomic v1.0.1 // indirect
github.com/viterin/partial v1.1.0 // indirect
github.com/viterin/vek v0.4.2 // indirect
golang.org/x/sys v0.11.0 // indirect
Expand Down
2 changes: 2 additions & 0 deletions go.sum
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Expand Up @@ -4,6 +4,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/google/renameio v1.0.1 h1:Lh/jXZmvZxb0BBeSY5VKEfidcbcbenKjZFzM/q0fSeU=
github.com/google/renameio v1.0.1/go.mod h1:t/HQoYBZSsWSNK35C6CO/TpPLDVWvxOHboWUAweKUpk=
github.com/natefinch/atomic v1.0.1 h1:ZPYKxkqQOx3KZ+RsbnP/YsgvxWQPGxjC0oBt2AhwV0A=
github.com/natefinch/atomic v1.0.1/go.mod h1:N/D/ELrljoqDyT3rZrsUmtsuzvHkeB/wWjHV22AZRbM=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
Expand Down