sampling from a distribution and from a choice

src/storm/generator/Choice.cpp

@@ -45,6 +45,11 @@ namespace storm {
             }
         }
 
+        template<typename ValueType, typename StateType>
+        StateType Choice<ValueType, StateType>::sampleFromDistribution(ValueType const& quantile) const {
+            return distribution.sampleFromDistribution(quantile);
+        }
+        
         template<typename ValueType, typename StateType>
         typename storm::storage::Distribution<ValueType, StateType>::iterator Choice<ValueType, StateType>::begin() {
             return distribution.begin();

src/storm/generator/Choice.h

@@ -29,6 +29,17 @@ namespace storm {
              */
             void add(Choice const& other);
 
+            /**
+             * Given a value q, find the event in the ordered distribution that corresponds to this prob.
+             * Example: Given a (sub)distribution { x -> 0.4, y -> 0.3, z -> 0.2 },
+             * A value q in [0,0.4] yields x, q in [0.4, 0.7] yields y, and q in [0.7, 0.9] yields z.
+             * Any other value for q yields undefined behavior.
+             *
+             * @param quantile q, a value in the CDF.
+             * @return A state
+             */
+            StateType sampleFromDistribution(ValueType const& quantile) const;
+            
             /*!
              * Returns an iterator to the distribution associated with this choice.
              *

src/storm/storage/Distribution.cpp

@@ -177,6 +177,20 @@ namespace storm {
             }
         }
 
+        template<typename ValueType, typename StateType>
+        StateType Distribution<ValueType, StateType>::sampleFromDistribution(const ValueType &quantile) const {
+            ValueType sum = storm::utility::zero<ValueType>();
+            storm::utility::ConstantsComparator<ValueType> comp;
+            for (auto const& entry: distribution) {
+                sum += entry.second;
+                if (comp.isLess(quantile,sum)) {
+                    return entry.first;
+                }
+            }
+            STORM_LOG_ASSERT(false,"This point should not be reached.");
+            return 0;
+        }
+    
         
         template class Distribution<double>;
         template std::ostream& operator<<(std::ostream& out, Distribution<double> const& distribution);

src/storm/storage/Distribution.h

@@ -149,6 +149,17 @@ namespace storm {
              */
             void normalize();
 
+            /**
+            * Given a value q, find the event in the ordered distribution that corresponds to this prob.
+            * Example: Given a (sub)distribution { x -> 0.4, y -> 0.3, z -> 0.2 },
+            * A value q in [0,0.4] yields x, q in [0.4, 0.7] yields y, and q in [0.7, 0.9] yields z.
+            * Any other value for q yields undefined behavior.
+            *
+            * @param quantile q, a value in the CDF.
+            * @return A state
+            */
+            StateType sampleFromDistribution(ValueType const& quantile) const;
+            
         private:
             // A list of states and the probabilities that are assigned to them.
             container_type distribution;