Document result distribution and implement as part of qsim app

app/qir-qsim.cc

@@ -8,14 +8,11 @@
 #include <cstdlib>
 #include <iostream>
 #include <string>
-#include <string_view>
 #include <CLI/CLI.hpp>
 
-#include "qiree_version.h"
-
 #include "qiree/Executor.hh"
 #include "qiree/Module.hh"
-#include "qiree/QuantumNotImpl.hh"
+#include "qiree/ResultDistribution.hh"
 #include "qirqsim/QsimDefaultRuntime.hh"
 #include "qirqsim/QsimQuantum.hh"
 
@@ -25,50 +22,25 @@ namespace qiree
 {
 namespace app
 {
+//---------------------------------------------------------------------------//
 void run(std::string const& filename, int num_shots)
-// bool group_tuples = false)
 {
     // Load the input
     Executor execute{Module{filename}};
 
     // Set up qsim
     QsimQuantum sim(std::cout, 0);
-
-    // Collect the statistics
-    std::unique_ptr<RuntimeInterface> rt;
-    rt = std::make_unique<QsimDefaultRuntime>(std::cout, sim);
+    QsimDefaultRuntime rt(std::cout, sim);
+    ResultDistribution distribution;
 
     // Run several time = shots (default 1)
     for (int i = 0; i < num_shots; i++)
     {
-        execute(sim, *rt);
+        execute(sim, rt);
+        distribution.accumulate(rt.result());
     }
 
-    std::cout << std::endl;
-    std::cout << "Measurement output:" << std::endl;
-    std::cout << "-------------------" << std::endl;
-    std::cout << "Number of shots: " << num_shots << std::endl;
-    std::cout << "Number of qubits: " << sim.num_qubits() << std::endl;
-
-    for (int q_index = 0; q_index < sim.num_qubits(); q_index++)
-    {
-        int value_0 = 0;
-        int value_1 = 0;
-        if (auto value
-            = sim.manager.getBufferValue("q" + std::to_string(q_index), "0");
-            value.has_value())
-        {
-            value_0 = value.value();
-        }
-        if (auto value
-            = sim.manager.getBufferValue("q" + std::to_string(q_index), "1");
-            value.has_value())
-        {
-            value_1 = value.value();
-        }
-        std::cout << "q" << q_index << " {0: " << value_0 << ","
-                  << " 1: " << value_1 << "}\n";
-    }
+    std::cout << distribution.to_json() << std::endl;
 }
 
 //---------------------------------------------------------------------------//
@@ -83,7 +55,6 @@ int main(int argc, char* argv[])
 {
     int num_shots{1};
     std::string filename;
-    // bool group_tuples{false};
 
     CLI::App app;
 
@@ -95,14 +66,8 @@ int main(int argc, char* argv[])
         = app.add_option("-s,--shots", num_shots, "Number of shots");
     nshot_opt->capture_default_str();
 
-    // app.add_flag("--group-tuples,!--no-group-tuples",
-    //             group_tuples,
-    //             "Print per-tuple measurement statistics rather than "
-    //             "per-qubit");
-
     CLI11_PARSE(app, argc, argv);
 
-    // qiree::app::run(filename, num_shots, group_tuples);
     qiree::app::run(filename, num_shots);
 
     return EXIT_SUCCESS;

src/qiree/ResultDistribution.hh

@@ -16,14 +16,17 @@ class RecordedResult;
 //---------------------------------------------------------------------------//
 /*!
  * Distribution of recorded results from shots.
-
-The distribution is formed by accumulating multiple \c RecordedResult
-instances into a sparse map of {bit string -> count}. The length of the bit
-string is the same for all keys. We provide accessors by string key such
-as \c 01001 which corresponds to a bit string `{false, true, ...}`. It is
-serializable to JSON, creating an object that has bit strings as keys and
-counts as values.
-
+ * The distribution is formed by accumulating multiple \c RecordedResult
+ * instances into a sparse map of {bit string -> count}. The length of the bit
+ * string is the same for all keys. We provide accessors by little-endian
+ * string key such as \c "01001" which corresponds to a bit string \code
+ * {false, true, false, false, true}
+ * \endcode
+ * Little-endian is an "array-like" representation (the initial
+ * character corresponds to the zeroth qubit) rather than a "number-like"
+ * representation (i.e., a base-2 encoding of the qubits). It is serializable
+ * to JSON, creating an object that has bit strings as keys and counts as
+ * values.
  */
 class ResultDistribution
 {