Add some comments

utils/ioda_example/gdas_meanioda.h

@@ -11,6 +11,12 @@
 #include "oops/util/Logger.h"
 
 namespace gdasapp {
+  // this is an example of how one can use OOPS and IODA to do something
+  // in this code, we will read in configuration from YAML
+  // and then use that configuration to read in a IODA formatted file,
+  // read one group/variable (with optional channel)
+  // and compute and print out the mean of the variable.
+  // Nothing fancy, but you can see how this could be expanded!
 
   class IodaExample : public oops::Application {
    public:
@@ -23,7 +29,7 @@ namespace gdasapp {
       // get the obs space configuration
       const eckit::LocalConfiguration obsConfig(fullConfig, "obs space");
       ioda::ObsTopLevelParameters obsparams;
-      obsparams.validateAndDeserialize(obsConfig);
+      obsparams.validateAndDeserialize(obsConfig);  // TODO CRM, can I remove this and then the simulated vars junk??
       oops::Log::info() << "obs space: " << std::endl << obsConfig << std::endl;
       // time window stuff
       std::string winbegin;
@@ -40,20 +46,25 @@ namespace gdasapp {
         fullConfig.get("channel", chan);
       }
       // read the obs space
+      // Note, the below line does a lot of heavy lifting
+      // we can probably go to a lower level function (and more of them) to accomplish the same thing
       ioda::ObsSpace ospace(obsparams, oops::mpi::world(), util::DateTime(winbegin), util::DateTime(winend), oops::mpi::myself());
       const size_t nlocs = ospace.nlocs();
       oops::Log::info() << "nlocs =" << nlocs << std::endl;
       std::vector<float> buffer(nlocs);
+      // below is grabbing from the IODA obs space the specified group/variable and putting it into the buffer
       if (chan == 0) {
         // no channel is selected
         ospace.get_db(group, variable, buffer);
       } else {
         // give it the channel as a single item list
         ospace.get_db(group, variable, buffer, {chan});
       }
+      // the below line computes the mean, aka sum divided by count
       const float mean = std::reduce(buffer.begin(), buffer.end()) / float(nlocs);
+      // write the mean out to the stdout
       oops::Log::info() << "mean value for " << group << "/" << variable << "=" << mean << std::endl;
-
+      // a better program should return a real exit code depending on result, but this is just an example!
       return 0;
     }
     // -----------------------------------------------------------------------------