Merge pull request #2980 from rcurtin/dataset-info-resize-fix

LoadCSV: only reset the DatasetMapper if the dimensionality is wrong.

HISTORY.md

@@ -61,6 +61,8 @@
 
   * Fix Julia model serialization bug (#2970).
 
+  * Fix `LoadCSV()` to use pre-populated `DatasetInfo` objects (#2980).
+
 ### mlpack 3.4.2
 ###### 2020-10-26
   * Added Mean Absolute Percentage Error.

src/mlpack/core/data/load.hpp

@@ -273,8 +273,12 @@ bool Load(const std::string& filename,
  * mlpack requires column-major matrices, this should be left at its default
  * value of 'true'.
  *
- * The DatasetMapper object passed to this function will be re-created, so any
- * mappings from previous loads will be lost.
+ * If the given `info` has already been used with a different `data::Load()`
+ * call where the dataset has the same dimensionality, then the mappings and
+ * dimension types inside of `info` will be *re-used*.  If the given `info` is a
+ * new `DatasetMapper` object (e.g. its dimensionality is 0), then new mappings
+ * will be created.  If the given `info` has a different dimensionality of data
+ * than what is present in `filename`, an exception will be thrown.
  *
  * @param filename Name of file to load.
  * @param matrix Matrix to load contents of file into.

src/mlpack/core/data/load_csv.hpp

@@ -96,7 +96,20 @@ class LoadCSV
     {
       ++rows;
     }
-    info = DatasetMapper<MapPolicy>(rows);
+
+    // Reset the DatasetInfo object, if needed.
+    if (info.Dimensionality() == 0)
+    {
+      info.SetDimensionality(rows);
+    }
+    else if (info.Dimensionality() != rows)
+    {
+      std::ostringstream oss;
+      oss << "data::LoadCSV(): given DatasetInfo has dimensionality "
+          << info.Dimensionality() << ", but data has dimensionality "
+          << rows;
+      throw std::invalid_argument(oss.str());
+    }
 
     // Now, jump back to the beginning of the file.
     inFile.clear();
@@ -179,8 +192,19 @@ class LoadCSV
         qi::parse(line.begin(), line.end(),
             stringRule[findRowSize] % delimiterRule);
 
-        // Now that we know the dimensionality, initialize the DatasetMapper.
-        info.SetDimensionality(rows);
+        // Reset the DatasetInfo object, if needed.
+        if (info.Dimensionality() == 0)
+        {
+          info.SetDimensionality(rows);
+        }
+        else if (info.Dimensionality() != rows)
+        {
+          std::ostringstream oss;
+          oss << "data::LoadCSV(): given DatasetInfo has dimensionality "
+              << info.Dimensionality() << ", but data has dimensionality "
+              << rows;
+          throw std::invalid_argument(oss.str());
+        }
       }
 
       // If we need to do a first pass for the DatasetMapper, do it.