uhd: math: Add interpolation.hpp

- Moves linear_interp from cal to utils
- Moves the interp_mode enum class to interpolation.hpp
- Adds three interpolation methods for maps: at_interpolate_1d(),
  at_nearest(), at_lin_interp()
- Adds unit tests

1 files changed, 35 insertions, 0 deletions

diff --git a/host/tests/interpolation_test.cpp b/host/tests/interpolation_test.cpp
new file mode 100644
index 000000000..b3314c34a
--- /dev/null
+++ b/host/tests/interpolation_test.cpp
@@ -0,0 +1,35 @@
+//
+// Copyright 2020 Ettus Research, a National Instruments Brand
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#include <uhdlib/utils/interpolation.hpp>
+#include <boost/test/unit_test.hpp>
+
+BOOST_AUTO_TEST_CASE(test_interp)
+{
+    const double x0 = 1.0, x1 = 2.0;
+    const double y0 = 2.0, y1 = 4.0;
+    const double x     = 1.5;
+    const double y_exp = 3.0;
+
+    BOOST_CHECK_EQUAL(uhd::math::linear_interp<double>(x, x0, y0, x1, y1), y_exp);
+}
+
+BOOST_AUTO_TEST_CASE(test_map_interp)
+{
+    using namespace uhd::math;
+    std::map<double, double> test_data{{1.0, 1.0}, {2.0, 2.0}, {3.0, 3.0}};
+
+    BOOST_CHECK_EQUAL(at_nearest(test_data, 1.1), 1.0);
+    BOOST_CHECK_EQUAL(at_nearest(test_data, 1.9), 2.0);
+    BOOST_CHECK_EQUAL(at_nearest(test_data, 2.1), 2.0);
+    BOOST_CHECK_EQUAL(at_nearest(test_data, 1e9), 3.0);
+
+    BOOST_CHECK_CLOSE(at_lin_interp(test_data, 1.5), 1.5, 1e-6);
+    BOOST_CHECK_EQUAL(at_lin_interp(test_data, 0.1), 1.0);
+    BOOST_CHECK_EQUAL(at_lin_interp(test_data, 2.0), 2.0);
+    BOOST_CHECK_EQUAL(at_lin_interp(test_data, 137.0), 3.0);
+}
+