[IMP-dev] Remove uniform_01 from Monte Carlo code

[Ben Webb <>]

The attached patch removes the code from the Monte Carlo 
NormalMover::generate_move method that uses boost::uniform_01, and 
replaces it with code that uses boost::variate_generator instead. This 
is because uniform_01 takes the random number generator by value rather 
than reference; thus, it creates a temporary copy of it and doesn't 
update the generator state (so that every time you call the method, you 
get the same result, unless you call some other method somewhere which 
_does_ update the RNG). At least, this is what was happening in the MD 
code, which also used uniform_01, until I fixed it in r454.

variate_generator in the attached patch takes a reference to the 
underlying RNG, so *does* update the state. variate_generator seems to 
be the "official" Boost way to tie a distribution with a random number 
generator these days anyway.

Comments?

	Ben
--
                      http://salilab.org/~ben/
"It is a capital mistake to theorize before one has data."
	- Sir Arthur Conan Doyle

Index: kernel/src/optimizers/movers/NormalMover.cpp
===================================================================
--- kernel/src/optimizers/movers/NormalMover.cpp	(revision 452)
+++ kernel/src/optimizers/movers/NormalMover.cpp	(working copy)
@@ -26,13 +26,15 @@
 
 void NormalMover::generate_move(float scale)
 {
-  std::vector<Float> center(number_of_float_keys());
-  boost::uniform_01<RandomNumberGenerator> u01(random_number_generator);
   boost::normal_distribution<double> mrng(0, stddev_);
+  boost::variate_generator<RandomNumberGenerator&,
+                           boost::normal_distribution<double> >
+                          sampler(random_number_generator, mrng);
+
   for (unsigned int i = 0; i < number_of_particles(); ++i) {
     for (unsigned int j = 0; j < number_of_float_keys(); ++j) {
       float c = get_float(i, j);
-      float r = mrng(u01);
+      float r = sampler();
       // Check for NaN (x!=x when x==NaN) (can only use std::isnan with C99)
       IMP_assert(r == r, "Bad random");
       IMP_assert(c == c, "Bad stored");