adding rad2diam utility function with test

Author: zdaq12

src/pypartmc.cpp

@@ -201,6 +201,11 @@ PYBIND11_MODULE(_PyPartMC, m) {
         "Convert mass-equivalent volume (m^3) to geometric radius (m) for spherical particles."
     );
 
+    m.def(
+        "rad2diam", &rad2diam, py::return_value_policy::copy,
+        "Convert radius (m) to diameter (m)."
+    );
+
     m.attr("__version__") = MACRO_STRINGIFY(VERSION_INFO);
 
     m.attr("__all__") = py::make_tuple(
@@ -218,6 +223,7 @@ PYBIND11_MODULE(_PyPartMC, m) {
         "pow2_above",
         "histogram_1d",
         "histogram_2d",
-        "sphere_vol2rad"
+        "sphere_vol2rad",
+        "rad2diam"
     );
 }

src/util.F90

@@ -27,4 +27,12 @@ subroutine f_sphere_vol2rad(v, rad) bind(C)
 
 end subroutine
 
+subroutine f_rad2diam(rad, d) bind(C)
+   real(c_double), intent(in) :: rad
+   real(c_double), intent(out) :: d
+
+   d = rad2diam(rad)
+
+end subroutine
+
 end module

src/util.hpp

@@ -8,6 +8,7 @@
 
 extern "C" void py_pow2_above(int*, int*);
 extern "C" void f_sphere_vol2rad(const double*, double*);
+extern "C" void f_rad2diam(const double*, double*);
 
 auto pow2_above(int n) {
     int res;
@@ -21,5 +22,11 @@ double sphere_vol2rad(double v) {
     return rad;
 }
 
+double rad2diam(double rad) {
+    double d;
+    f_rad2diam(&rad, &d);
+    return  d;
+}
+
 extern "C" double py_deg2rad(double);
 

tests/test_util.py

@@ -34,3 +34,14 @@ def test_sphere_vol2rad():
 
         # assert
         np.testing.assert_almost_equal(1e-6, rad)
+
+    @staticmethod
+    def test_rad2diam():
+        # arrange
+        arg = 0.5e-6
+
+        # act
+        diam = ppmc.rad2diam(arg)
+
+        # assert
+        assert diam == 2*arg