add symbol and symbolic forward check for histogram

python/mxnet/ndarray/ndarray.py

@@ -3754,7 +3754,7 @@ def histogram(a, bins=10, range=None):
         If bins is an int, it defines the number of equal-width bins in the
         given range (10, by default). If bins is a sequence, it defines the bin edges,
         including the rightmost edge, allowing for non-uniform bin widths.
-    range_ : (float, float), optional
+    range : (float, float), optional
         The lower and upper range of the bins. If not provided, range is simply (a.min(), a.max()).
         Values outside the range are ignored. The first element of the range must be less than or
         equal to the second. range affects the automatic bin computation as well, the range will
@@ -3766,7 +3766,7 @@ def histogram(a, bins=10, range=None):
         return _internal._histogram(data=a, bins=bins)
     elif isinstance(bins, integer_types):
         if range is None:
-            warnings.warn("range_ is not specified, using numpy's result "
+            warnings.warn("range is not specified, using numpy's result "
                           "to ensure consistency with numpy")
             res, bin_bounds = np.histogram(a.asnumpy(), bins=bins)
             return array(res), array(bin_bounds)

python/mxnet/symbol/symbol.py

@@ -34,7 +34,7 @@
 
 from ..attribute import AttrScope
 from ..base import _LIB, numeric_types, c_array, c_array_buf, c_str, c_str_array, c_handle_array
-from ..base import mx_uint, py_str, string_types
+from ..base import mx_uint, py_str, string_types, integer_types
 from ..base import NDArrayHandle, ExecutorHandle, SymbolHandle
 from ..base import check_call, MXNetError, NotImplementedForSymbol
 from ..context import Context, current_context
@@ -47,7 +47,8 @@
 from ._internal import SymbolBase, _set_symbol_class
 
 __all__ = ["Symbol", "var", "Variable", "Group", "load", "load_json",
-           "pow", "maximum", "minimum", "hypot", "eye", "zeros", "ones", "full", "arange"]
+           "pow", "maximum", "minimum", "hypot", "eye", "zeros", "ones", "full", "arange",
+           "histogram"]
 
 
 class Symbol(SymbolBase):
@@ -2862,4 +2863,29 @@ def arange(start, stop=None, step=1.0, repeat=1, name=None, dtype=None):
     return _internal._arange(start=start, stop=stop, step=step, repeat=repeat,
                              name=name, dtype=dtype)
 
+def histogram(a, bins=10, range=None, **kwargs):
+    """Compute the histogram of the input data.
+
+    Parameters
+    ----------
+    a : NDArray
+        Input data. The histogram is computed over the flattened array.
+    bins : int or sequence of scalars
+        If bins is an int, it defines the number of equal-width bins in the
+        given range (10, by default). If bins is a sequence, it defines the bin edges,
+        including the rightmost edge, allowing for non-uniform bin widths.
+    range : (float, float), required if bins is an integer
+        The lower and upper range of the bins. If not provided, range is simply (a.min(), a.max()).
+        Values outside the range are ignored. The first element of the range must be less than or
+        equal to the second. range affects the automatic bin computation as well, the range will
+        be equally divided by the number of bins.
+    """
+    if isinstance(bins, Symbol):
+        return _internal._histogram(data=a, bins=bins, **kwargs)
+    elif isinstance(bins, integer_types):
+        if range is None:
+            raise ValueError("null range is not supported in symbol mode")
+        return _internal._histogram(data=a, bin_cnt=bins, range=range, **kwargs)
+    raise ValueError("bins argument should be either an integer or an NDArray")
+
 _set_symbol_class(Symbol)

src/operator/tensor/histogram.cc

@@ -138,7 +138,10 @@ Example::
 .set_num_outputs(2)
 .set_attr<nnvm::FListInputNames>("FListInputNames",
   [](const NodeAttrs& attrs) {
-    return std::vector<std::string>{"data", "bins"};
+    const HistogramParam& params = nnvm::get<HistogramParam>(attrs.parsed);
+    return params.bin_cnt.has_value() ?
+           std::vector<std::string>{"data"} :
+           std::vector<std::string>{"data", "bins"};
   })
 .set_attr<FResourceRequest>("FResourceRequest",
   [](const NodeAttrs& attrs) {

tests/python/unittest/test_operator.py

@@ -6024,6 +6024,18 @@ def f(x, bins=10, range=None):
         assert_almost_equal(mx_histo2.asnumpy(), np_histo2, rtol=1e-3, atol=1e-5)
         assert_almost_equal(mx_bins2.asnumpy(), np_bins2, rtol=1e-3, atol=1e-5)
 
+        data = mx.sym.Variable("data")
+
+        bins = mx.sym.Variable("bins")
+        histo1 = mx.sym.histogram(a=data, bins=bin_cnt, range=bin_range)
+        histo2 = mx.sym.histogram(a=data, bins=bins)
+        executor1 = histo1.bind(ctx=default_context(), args={"data" : x})
+        executor1.forward(is_train=False)
+        assert_almost_equal(np_histo1, executor1.outputs[0].asnumpy(), 0, 0, ("EXPECTED_histo1", "FORWARD_histo1"), equal_nan=False)
+        executor2 = histo2.bind(ctx=default_context(), args={"data" : x, "bins" : mx_bins})
+        executor2.forward(is_train=False)
+        assert_almost_equal(np_histo2, executor2.outputs[0].asnumpy(), 0, 0, ("EXPECTED_histo2", "FORWARD_histo2"), equal_nan=False)
+
 
 def test_op_output_names_monitor():
     def check_name(op_sym, expected_names):