(spark) branch branch-4.x updated: [MINOR][CORE] Fix swapped depth/width formulas in CountMinSketch class doc

[ma...@apache.org]

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MaxGekk pushed a commit to branch branch-4.x
in repository https://gitbox.apache.org/repos/asf/spark.git


The following commit(s) were added to refs/heads/branch-4.x by this push:
     new fe85bf284e7e [MINOR][CORE] Fix swapped depth/width formulas in CountMinSketch class doc
fe85bf284e7e is described below

commit fe85bf284e7eeb4d92101b00ee3793c3eed9c29b
Author: YangJie <ya...@baidu.com>
AuthorDate: Tue Jun 30 13:39:43 2026 +0200

    [MINOR][CORE] Fix swapped depth/width formulas in CountMinSketch class doc
    
    ### What changes were proposed in this pull request?
    
    This PR fixes the class-level Javadoc of `org.apache.spark.util.sketch.CountMinSketch`, which assigned the two table dimensions to the wrong symbols. The doc previously read:
    
    ```
    d = ceil(2 / eps)
    w = ceil(-log(1 - confidence) / log(2))
    ```
    
    but the implementation (`CountMinSketchImpl`, the `(eps, confidence, seed)` constructor) actually sets:
    
    ```java
    this.width = (int) Math.ceil(2 / eps);
    this.depth = (int) Math.ceil(-Math.log1p(-confidence) / Math.log(2));
    ```
    
    i.e. `width` is derived from `eps` and `depth` from `confidence` -- the opposite of what the doc stated. The fix swaps the two lines so the doc matches the code:
    
    ```
    w = ceil(2 / eps)
    d = ceil(-log(1 - confidence) / log(2))
    ```
    
    ### Why are the changes needed?
    
    Doc fix
    
    ### Does this PR introduce _any_ user-facing change?
    
    No. Documentation-only change; no behavior, serialization, or API impact.
    
    ### How was this patch tested?
    
    Pass Github Actions
    
    ### Was this patch authored or co-authored using generative AI tooling?
    
    Generated-by: Claude Code
    
    Closes #56897 from LuciferYang/minor-countminsketch-doc-fix.
    
    Authored-by: YangJie <ya...@baidu.com>
    Signed-off-by: Max Gekk <ma...@gmail.com>
    (cherry picked from commit 1409d88cfaab416b5bf61b875408418761004bb5)
    Signed-off-by: Max Gekk <ma...@gmail.com>
---
 .../src/main/java/org/apache/spark/util/sketch/CountMinSketch.java    | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java b/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java
index 06a248c9a27c..cc958f947b4d 100644
--- a/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java
+++ b/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java
@@ -45,8 +45,8 @@ import java.io.OutputStream;
  * Under the cover, a {@link CountMinSketch} is essentially a two-dimensional {@code long} array
  * with depth {@code d} and width {@code w}, where
  * <ul>
- *   <li>{@code d = ceil(2 / eps)}</li>
- *   <li>{@code w = ceil(-log(1 - confidence) / log(2))}</li>
+ *   <li>{@code w = ceil(2 / eps)}</li>
+ *   <li>{@code d = ceil(-log(1 - confidence) / log(2))}</li>
  * </ul>
  *
  * This implementation is largely based on the {@code CountMinSketch} class from stream-lib.


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