[RELAY] Add sigmoid relay operator (#1836)

docs/langref/relay_op.rst

@@ -25,6 +25,7 @@ This level enables fully connected multi-layer perceptron.
    tvm.relay.log
    tvm.relay.sqrt
    tvm.relay.exp
+   tvm.relay.sigmoid
    tvm.relay.add
    tvm.relay.expand_dims
 
@@ -61,6 +62,7 @@ Level 1 Definitions
 .. autofunction:: tvm.relay.log
 .. autofunction:: tvm.relay.sqrt
 .. autofunction:: tvm.relay.exp
+.. autofunction:: tvm.relay.sigmoid
 .. autofunction:: tvm.relay.add
 
 

python/tvm/relay/op/tensor.py

@@ -60,6 +60,22 @@ def sqrt(data):
     return _make.sqrt(data)
 
 
+def sigmoid(data):
+    """Compute elementwise sigmoid of data.
+
+    Parameters
+    ----------
+    data : relay.Expr
+        The input data
+
+    Returns
+    -------
+    result : relay.Expr
+        The computed result.
+    """
+    return _make.sigmoid(data)
+
+
 def add(lhs, rhs):
     """Addition with numpy-style broadcasting.
 

src/relay/op/tensor/unary.cc

@@ -65,6 +65,17 @@ RELAY_REGISTER_UNARY_OP("sqrt")
 .add_type_rel("Identity", IdentityRel);
 
 
+RELAY_REGISTER_UNARY_OP("sigmoid")
+.describe(R"code(Returns the sigmoid input array, computed element-wise.
+
+.. math::
+   sigmoid(x)
+
+)code" TVM_ADD_FILELINE)
+.set_support_level(1)
+.add_type_rel("Identity", IdentityRel);
+
+
 // Concat
 TVM_REGISTER_API("relay.op._make.concat")
   .set_body_typed<Expr(Expr)>([](Expr tuple) {

tests/python/relay/test_op_level1.py

@@ -16,5 +16,21 @@ def test_expand_dims_infer_type():
         (n, t, 1, 100), "float32")
 
 
+def test_unary_op():
+    for op in [relay.exp,
+               relay.log,
+               relay.sqrt,
+               relay.sigmoid]:
+        ib = relay.ir_builder.IRBuilder()
+        x = ib.param("x", relay.TensorType((10, 4), "int32"))
+        with ib.function(x) as func:
+            ib.ret(op(x.var))
+        ib.ret(func)
+        func = relay.ir_pass.infer_type(ib.env, func.to_func())
+        ftype = func.checked_type()
+        assert ftype.ret_type == relay.TensorType((10, 4), "int32")
+
+
 if __name__ == "__main__":
     test_expand_dims_infer_type()
+    test_unary_op()