math

README.md

@@ -21,9 +21,10 @@ Jngen library provides several handy instruments for generating various kinds of
 * [[options.h] Parsing command-line options](/doc/getopt.md)
 * [[array.h] Array: wrapper for std::vector](/doc/array.md)
 * [[repr.h, printers.h] Printers and output modifiers](/doc/printers.md)
-* [[generic_graph.h] Graphs and trees: bacics](/doc/generic_graph.md)
+* [[generic_graph.h] Graphs and trees: basics](/doc/generic_graph.md)
     * [[graph.h] Graphs generation](/doc/graph.md)
     * [[tree.h] Trees generation](/doc/tree.md)
+* [[math.h] Math: primes and partitions](/doc/math.md)
 
 ### Examples
 Generate a random tree on *n* vertices with a 3-letter string assigned to each edge:

doc/math.md

@@ -0,0 +1,31 @@
+## Math-ish primitives
+
+Jngen provides several free functions and a generator class *MathRandom* to help generating numbers and combinatorial primitives. All interaction with *MathRandom* goes via its global instance called *rndm*. The source of randomness is *rnd*.
+
+### Standalone functions
+
+#### bool isPrime(long long n)
+* Returns: true if *n* is prime, false otherwise.
+* Supported for all *n* from 1 to 3.8e18.
+* Implemented with deterministic variation of the Miller-Rabin primality test so should work relatively fast (exact benchmark here).
+
+### MathRandom methods
+
+#### long long randomPrime(long long n)
+#### long long randomPrime(long long l, long long r)
+* Returns: random prime in range *[2, n)* or *[l, r]* respectively.
+* Throws if no prime is found on the interval.
+
+#### Array partition(int n, int numParts)
+#### Array partitionNonEmpty(int n, int numParts)
+#### Array64 partition(long long n, int numParts)
+#### Array64 partitionNonEmpty(long long n, int numParts)
+* Returns: a random ordered partition of *n* into *numParts* parts. In case of *partitionNonEmpty* each element of the result is positive.
+
+#### template&lt;typename T> <br> TArray&lt;TArray&lt;T>> partition(TArray&lt;T> elements, int numParts)
+#### template&lt;typename T> <br> TArray&lt;TArray&lt;T>> partitionNonEmpty(TArray&lt;T> elements, int numParts)
+* Returns: a random partition of the array *elements* into *numParts* parts.
+
+#### template&lt;typename T> <br> TArray&lt;TArray&lt;T>> partitionNonEmpty(TArray&lt;T> elements, const Array& sizes)
+* Returns: a random partition of the array *elements* into parts, where the size of each part is specified.
+* Note: sum(*sizes*) must be equal to *elements.size()*.