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Posted to github@arrow.apache.org by "js8544 (via GitHub)" <gi...@apache.org> on 2023/07/28 14:56:53 UTC

[GitHub] [arrow] js8544 opened a new pull request, #36932: GH-36931: [C++] Add cumulative_mean function

js8544 opened a new pull request, #36932:
URL: https://github.com/apache/arrow/pull/36932

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   If this is not a [minor PR](https://github.com/apache/arrow/blob/main/CONTRIBUTING.md#Minor-Fixes). Could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose
   
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   Then could you also rename the pull request title in the following format?
   
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   ### Rationale for this change
   
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   Add `cumulative_mean` function
   
   ### What changes are included in this PR?
   
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   There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR.
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   Implement `cumulative_mean` function. The current cumulative_* kernel generator can only be based on a simple binary arithmetic op and the state can only be a single value. I refactored it to using of a generic state such that it can handle complex operations such as `mean`, `median`, `var` etc.
   
   ### Are these changes tested?
   
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   Yes
   
   ### Are there any user-facing changes?
   No
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   <!-- **This PR contains a "Critical Fix".** -->


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[GitHub] [arrow] js8544 commented on a diff in pull request #36932: GH-36931: [C++] Add cumulative_mean function

Posted by "js8544 (via GitHub)" <gi...@apache.org>.

js8544 commented on code in PR #36932:
URL: https://github.com/apache/arrow/pull/36932#discussion_r1288501904


##########
cpp/src/arrow/compute/kernels/vector_cumulative_ops.cc:
##########
@@ -217,53 +253,142 @@ const FunctionDoc cumulative_min_doc{
      "start as the new minimum)."),
     {"values"},
     "CumulativeOptions"};
+
+const FunctionDoc cumulative_mean_doc{
+    "Compute the cumulative mean over a numeric input",
+    ("`values` must be numeric. Return an array/chunked array which is the\n"
+     "cumulative mean computed over `values`. CumulativeOptions::start_value is \n"
+     "ignored."),
+    {"values"},
+    "CumulativeOptions"};
 }  // namespace
 
+// Kernel factory for simple arithmetic operations.
+// Op is a compute kernel representing any binary associative operation with
+// an identity element (add, product, min, max, etc.), i.e. ones that form a monoid.
+template <typename Op, typename OptionsType>
+struct CumulativeBinaryOpKernelFactory {

Review Comment:
   Thanks! This is a `Today I Learned` for me.



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