Add binary generators

In this commit, we add a set of binary generators to
generate discrete/binary versions of the swarm.

Signed-off-by: Lester James V. Miranda <ljvmiranda@gmail.com>

pyswarms/backend/generators.py

@@ -64,6 +64,42 @@ def generate_swarm(n_particles, dimensions, bounds=None, center=1.00, init_pos=N
     else:
         return pos
 
+def generate_discrete_swarm(n_particles, dimensions, binary=False, init_pos=None):
+    """Generates a discrete swarm
+    
+    Parameters
+    ----------
+    n_particles : int
+        number of particles to be generated in the swarm.
+    dimensions: int
+        number of dimensions to be generated in the swarm.
+    binary : bool (default is :code:`False`)
+        generate a binary matrix
+    init_pos : :code:`numpy.ndarray` (default is :code:`None`)
+        option to explicitly set the particles' initial positions. Set to
+        :code:`None` if you wish to generate the particles randomly.
+    """
+    try:
+        if init_pos is not None:
+            # There is user-defined initial position
+            if binary:
+                # Check if the initialized position is binary
+                if not len(np.unique(init_pos)) == 2:
+                    raise ValueError('User-defined init_pos is not binary!')
+                pos = init_pos
+            else:
+                pos = init_pos
+        else:
+            # There is no user-defined initial position
+            if binary:
+                pos = np.random.randint(2, size=(n_particles, dimensions))
+            else:
+                pos = np.random.random_sample(size=(n_particles, dimensions)).argsort(axis=1)
+    except ValueError:
+        raise
+    else:
+        return pos
+
 def generate_velocity(n_particles, dimensions, clamp=None):
     """Initializes a velocity vector
 
@@ -72,7 +108,7 @@ def generate_velocity(n_particles, dimensions, clamp=None):
     n_particles : int
         number of particles to be generated in the swarm.
     dimensions: int
-        number of dimensions to be generated in the swarm
+        number of dimensions to be generated in the swarm.
     clamp : tuple of floats (default is :code:`None`)
         a tuple of size 2 where the first entry is the minimum velocity
         and the second entry is the maximum velocity. It
@@ -93,8 +129,8 @@ def generate_velocity(n_particles, dimensions, clamp=None):
     else:
         return velocity
 
-def create_swarm(n_particles, dimensions, discrete=False, options=None,
-                 bounds=None, center=1.0, clamp=None):
+def create_swarm(n_particles, dimensions, discrete=False, binary=False,
+                options=None, bounds=None, center=1.0, init_pos=None, clamp=None):
     """Abstracts the generate_swarm() and generate_velocity() methods
     
     Parameters
@@ -107,12 +143,17 @@ def create_swarm(n_particles, dimensions, discrete=False, options=None,
         Swarm options, for example, c1, c2, etc.
     discrete : bool (default is :code:`False`)
         Creates a discrete swarm
+    binary : bool (default is :code:`False`)
+        generate a binary matrix
     bounds : tuple of :code:`np.ndarray` or list (default is :code:`None`)
         a tuple of size 2 where the first entry is the minimum bound while
         the second entry is the maximum bound. Each array must be of shape
         :code:`(dimensions,)`.
-    center : :code:`numpy.ndarrray` (default is :code:`1`)
+    center : :code:`numpy.ndarray` (default is :code:`1`)
         a list of initial positions for generating the swarm
+    init_pos : :code:`numpy.ndarray` (default is :code:`None`)
+        option to explicitly set the particles' initial positions. Set to
+        :code:`None` if you wish to generate the particles randomly.
     clamp : tuple of floats (default is :code:`None`)
         a tuple of size 2 where the first entry is the minimum velocity
         and the second entry is the maximum velocity. It
@@ -123,6 +164,11 @@ def create_swarm(n_particles, dimensions, discrete=False, options=None,
     pyswarms.backend.swarms.Swarm
         a Swarm class
     """
-    position = generate_swarm(n_particles, dimensions, bounds, center)
-    velocity = generate_velocity(n_particles, dimensions, clamp)
+    if discrete:
+        position = generate_discrete_swarm(n_particles, dimensions, binary=binary)
+    else:
+        position = generate_swarm(n_particles, dimensions, bounds=bounds,
+                                  center=center, init_pos=init_pos)
+
+    velocity = generate_velocity(n_particles, dimensions, clamp=clamp)
     return Swarm(position, velocity, options=options)