Randomly perturb the bundle adjustment problem.

1. Add the ability to perturb the camera pose and the
point positions using user specified parameters.
2. Re-order the flags.
3. Minor name correction.
4. Added Box-Mueller generator to random.h

Change-Id: I2c9ce74c237f5bde9a7299cc71b205d1ca9bc742

internal/ceres/random.h

diff --git a/internal/ceres/random.h b/internal/ceres/random.h
index 769e0b4..cd7a0ea 100644
--- a/internal/ceres/random.h
+++ b/internal/ceres/random.h
@@ -27,19 +27,41 @@
 // POSSIBILITY OF SUCH DAMAGE.
 //
 // Author: keir@google.com (Keir Mierle)
+//         sameeragarwal@google.com (Sameer Agarwal)
 
 #ifndef CERES_INTERNAL_RANDOM_H_
 #define CERES_INTERNAL_RANDOM_H_
 
+#include <cmath>
+#include <cstdlib>
+
 namespace ceres {
 
-inline double RandDouble() {
-  double r = rand();
-  return r / RAND_MAX;
+inline void SetRandomState(int state) {
+  srandom(state);
 }
 
 inline int Uniform(int n) {
-  return rand() % n;
+  return random() % n;
+}
+
+inline double RandDouble() {
+  double r = static_cast<double>(random());
+  return r / RAND_MAX;
+}
+
+// Box-Muller algorithm for normal random number generation.
+// http://en.wikipedia.org/wiki/Box-Muller_transform
+inline double RandNormal() {
+  double x1, x2, w;
+  do {
+    x1 = 2.0 * RandDouble() - 1.0;
+    x2 = 2.0 * RandDouble() - 1.0;
+    w = x1 * x1 + x2 * x2;
+  } while ( w >= 1.0 || w == 0.0 );
+
+  w = sqrt((-2.0 * log(w)) / w);
+  return x1 * w;
 }
 
 }  // namespace ceres