1 files changed, 46 insertions, 0 deletions
diff --git a/symbolic/generator.py b/symbolic/generator.py
new file mode 100644
index 0000000..e57154c
--- /dev/null
+++ b/symbolic/generator.py
@@ -0,0 +1,46 @@
+from sympy import *
+from sympy.codegen.ast import Assignment
+
+class LBM():
+    def __init__(self, descriptor):
+        self.descriptor = descriptor
+        self.f_next = symarray('f_next', descriptor.q)
+        self.f_curr = symarray('f_curr', descriptor.q)
+
+    def moments(self, optimize = True):
+        rho = symbols('rho')
+        u   = Matrix(symarray('u', self.descriptor.d))
+
+        exprs = [ Assignment(rho, sum(self.f_curr)) ]
+
+        for i, u_i in enumerate(u):
+            exprs.append(
+                Assignment(u_i, sum([ (c_j*self.f_curr[j])[i] for j, c_j in enumerate(self.descriptor.c) ]) / sum(self.f_curr)))
+
+        if optimize:
+            return cse(exprs, optimizations='basic', symbols=numbered_symbols(prefix='m'))
+        else:
+            return ([], exprs)
+
+    def equilibrium(self):
+        rho = symbols('rho')
+        u   = Matrix(symarray('u', self.descriptor.d))
+
+        f_eq = []
+
+        for i, c_i in enumerate(self.descriptor.c):
+            f_eq_i = self.descriptor.w[i] * rho * ( 1
+                                                  + c_i.dot(u)    /    self.descriptor.c_s**2
+                                                  + c_i.dot(u)**2 / (2*self.descriptor.c_s**4)
+                                                  - u.dot(u)      / (2*self.descriptor.c_s**2) )
+            f_eq.append(f_eq_i)
+
+        return f_eq
+
+    def bgk(self, tau, f_eq, optimize = True):
+        exprs = [ Assignment(self.f_next[i], self.f_curr[i] + 1/tau * (f_eq_i - self.f_curr[i])) for i, f_eq_i in enumerate(f_eq) ]
+
+        if optimize:
+            return cse(exprs, optimizations='basic')
+        else:
+            return ([], exprs)