stdlib: Add SparseHist to PyStats

This is inclusive of tests to ensure they have implemented correctly.

Change-Id: I5c84d5ffdb7b914936cfd86ca012a7b141eeaf42

src/python/m5/ext/pystats/statistic.py

@@ -253,3 +253,31 @@ class Distribution(Vector):
         # These check some basic conditions of a distribution.
         assert self.bin_size >= 0
         assert self.num_bins >= 1
+
+
+class SparseHist(Vector):
+    """A Sparse Histogram of values. A sparse histogram simply counts the "
+    frequency of each value in a sample. Ergo, it is, ineffect an disctionary
+    of values mapped to their count"""
+
+    def __init__(
+        self,
+        value: Dict[float, Scalar],
+        description: Optional[str] = None,
+    ):
+        super().__init__(
+            value=value,
+            type="SparseHist",
+            description=description,
+        )
+
+    def size(self) -> int:
+        """The number of unique sampled values."""
+        return len(self.value)
+
+    def count(self) -> int:
+        """
+        Returns the total number of samples.
+        """
+        assert self.value != None
+        return sum(self.value.values())

src/python/m5/stats/gem5stats.py

@@ -140,6 +140,8 @@ def __get_statistic(statistic: _m5.stats.Info) -> Optional[Statistic]:
         return __get_vector(statistic)
     elif isinstance(statistic, _m5.stats.Vector2dInfo):
         return __get_vector2d(statistic)
+    elif isinstance(statistic, _m5.stats.SparseHistInfo):
+        return __get_sparse_hist(statistic)
 
     return None
 
@@ -268,6 +270,24 @@ def __get_vector2d(statistic: _m5.stats.Vector2dInfo) -> Vector2d:
     return Vector2d(value=vector_rep, type="Vector2d", description=description)
 
 
+def __get_sparse_hist(statistic: _m5.stats.SparseHistInfo) -> SparseHist:
+    description = statistic.desc
+    value = statistic.values
+
+    parsed_values = {}
+    for val in value:
+        parsed_values[val] = Scalar(
+            value=value[val],
+            unit=statistic.unit,
+            datatype=StorageType["f64"],
+        )
+
+    return SparseHist(
+        value=parsed_values,
+        description=description,
+    )
+
+
 def _prepare_stats(group: _m5.stats.Group):
     """
     Prepares the statistics for dumping.

src/python/pybind11/stats.cc

@@ -78,6 +78,7 @@ cast_stat_info(const statistics::Info *info)
     TRY_CAST(statistics::VectorInfo);
     TRY_CAST(statistics::Vector2dInfo);
     TRY_CAST(statistics::DistInfo);
+    TRY_CAST(statistics::SparseHistInfo);
 
     return py::cast(info);
 
@@ -195,6 +196,15 @@ pybind_init_stats(py::module_ &m_native)
         .def_readonly("value", &statistics::Vector2dInfo::cvec)
         ;
 
+    py::class_<statistics::SparseHistInfo, statistics::Info,
+               std::unique_ptr<statistics::SparseHistInfo, py::nodelete>>(
+                    m, "SparseHistInfo")
+        .def_property_readonly("values", //A Dict[float, int] of sample & count
+            [](const statistics::SparseHistInfo &info) {
+                return info.data.cmap;
+            })
+        ;
+
     py::class_<statistics::FormulaInfo, statistics::VectorInfo,
                std::unique_ptr<statistics::FormulaInfo, py::nodelete>>(
                       m, "FormulaInfo")