[SPARK-58177][GRAPHX] Fix wrong operand in SVD++ aggregateMessages combiner#57314
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Ma77Ball wants to merge 1 commit into
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[SPARK-58177][GRAPHX] Fix wrong operand in SVD++ aggregateMessages combiner#57314Ma77Ball wants to merge 1 commit into
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cc @srowen @dongjoon-hyun @HyukjinKwon, PTAL when you have time. |
srowen
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Jul 16, 2026
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Yep, good catch, you are right.
I've long since lost my setup to merge PRs, so I hope someone else who's active can merge this.
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Hello @srowen, thank you for the information and I'll keep that in mind for the future. I greatly appreciate the review. |
HyukjinKwon
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Jul 19, 2026
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Thank you @uros-b and @HyukjinKwon for the review. For the regression test, I can open another Jira ticket and PR to work on this. Or would you prefer it to be done on this PR? |
Yicong-Huang
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I will help merge this then. Also LGTM
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…mbiner
### What changes were proposed in this pull request?
Fix the Phase-2 `aggregateMessages` combiner in `SVDPlusPlus.run`, which seeded the `_2` accumulator from the wrong operand:
```diff
- val out2 = g2._2.clone()
+ val out2 = g1._2.clone()
BLAS.nativeBLAS.daxpy(out2.length, 1.0, g2._2, 1, out2, 1)
```
### Why are the changes needed?
The next line adds `g2` on top, so the result should be `g1 + g2`. Because the code started with `g2` instead of `g1`, it computed `g2 + g2` and discarded `g1`. Any node with two or more edges ended up with the wrong value. The matching code just below already does it the right way (`g1 + g2`).
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Verified with a unit test (UT) that feeds two concrete updates through the combiner and checks the merged `_2` value, plus the existing suite: `build/sbt "graphx/testOnly org.apache.spark.graphx.lib.SVDPlusPlusSuite"` passes. With the faulty code, the output does not match the expected sum; with the fix, it does:
| | `_2` value |
|---|---|
| Input `g1._2` | `[3, 4]` |
| Input `g2._2` | `[30, 40]` |
| Expected (`g1._2 + g2._2`) | `[33, 44]` |
| Faulty code output | `[60, 80]` (wrong: `2 * g2._2`, drops `g1._2`) |
| Corrected code output | `[33, 44]` (correct) |
### Was this patch authored or co-authored using generative AI tooling?
No
Closes #57314 from Ma77Ball/SPARK-58177.
Authored-by: Matthew B. <mgball@uci.edu>
Signed-off-by: Yicong-Huang <17627829+Yicong-Huang@users.noreply.github.com>
(cherry picked from commit b5e242e)
Signed-off-by: Yicong-Huang <17627829+Yicong-Huang@users.noreply.github.com>
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What changes were proposed in this pull request?
Fix the Phase-2
aggregateMessagescombiner inSVDPlusPlus.run, which seeded the_2accumulator from the wrong operand:Why are the changes needed?
The next line adds
g2on top, so the result should beg1 + g2. Because the code started withg2instead ofg1, it computedg2 + g2and discardedg1. Any node with two or more edges ended up with the wrong value. The matching code just below already does it the right way (g1 + g2).Does this PR introduce any user-facing change?
No
How was this patch tested?
Verified with a unit test (UT) that feeds two concrete updates through the combiner and checks the merged
_2value, plus the existing suite:build/sbt "graphx/testOnly org.apache.spark.graphx.lib.SVDPlusPlusSuite"passes. With the faulty code, the output does not match the expected sum; with the fix, it does:_2valueg1._2[3, 4]g2._2[30, 40]g1._2 + g2._2)[33, 44][60, 80](wrong:2 * g2._2, dropsg1._2)[33, 44](correct)Was this patch authored or co-authored using generative AI tooling?
No