diff --git a/extension_cpp/csrc/include/extension/fast_sigmoid.h b/extension_cpp/csrc/include/extension/fast_sigmoid.h
new file mode 100644
index 0000000..c92e6bd
--- /dev/null
+++ b/extension_cpp/csrc/include/extension/fast_sigmoid.h
@@ -0,0 +1,13 @@
+#pragma once
+#include <torch/torch.h>
+
+namespace extension_cpp {
+
+TORCH_API torch::Tensor fast_sigmoid(
+    const torch::Tensor& input,
+    double min = -10.0,
+    double max = 10.0,
+    int64_t num_entries = 1000
+);
+
+} // namespace extension_cpp