[I] [Refactor] Add FloatElem trait and DataReader [mahout]

["0lai0 (via GitHub)" <gi...@apache.org>]

0lai0 opened a new issue, #1339:
URL: https://github.com/apache/mahout/issues/1339

   ### What
   
   Generalize `DataReader` from `Vec<f64>` to `Vec<T>` by introducing a `FloatElem` trait, so that `dtype=f32` data from file sources can stay as `f32` through the entire read path.
   
   ### Why
   
   `DataReader::read_batch` returns `Vec<f64>` only (`qdp-core/src/reader.rs`; the comment at line 100 marks this as structural debt). Until this is fixed, `dtype=f32` file sources are silently cast to f64, preventing a true f32 pipeline.
   
   ### How
   
   - Add `FloatElem` marker trait with `f32` / `f64` impls (or reuse existing `Dtype` mapping) in `qdp-core/src/types.rs` or a new `qdp-core/src/float_elem.rs`
   - Change `DataReader` → `DataReader<T: FloatElem>`, `read_batch -> Result<(Vec<T>, usize, usize)>`
   - Update `StreamingDataReader<T>` the same way
   - Fix call sites that no longer compile (minimal — non-Parquet readers may still produce `f64` for now)
   - No behavior change on existing `f64` paths; trait docs explain the f32 end-to-end goal
   
   **Out of scope:** Parquet schema/cast logic, pipeline_runner wiring
   **Acceptance criteria:**
   - [ ] `cargo test -p qdp-core` passes on Linux
   - [ ] Trait docs explain f32 end-to-end goal
   - [ ] No behavior change on existing f64 paths
   
   


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Re: [I] [Refactor] Add FloatElem trait and DataReader [mahout]

["guan404ming (via GitHub)" <gi...@apache.org>]

guan404ming closed issue #1339: [Refactor] Add FloatElem trait and DataReader<T>
URL: https://github.com/apache/mahout/issues/1339


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