messing around

sand.py

@@ -0,0 +1,36 @@
+import math
+
+x = 3 # example values
+y = -4
+
+# forward pass
+sigy = 1.0 / (1 + math.exp(-y)) # sigmoid in numerator   #(1)
+num = x + sigy # numerator                               #(2)
+sigx = 1.0 / (1 + math.exp(-x)) # sigmoid in denominator #(3)
+xpy = x + y                                              #(4)
+xpysqr = xpy**2                                          #(5)
+den = sigx + xpysqr # denominator                        #(6)
+invden = 1.0 / den                                       #(7)
+f = num * invden # done!                                 #(8)
+
+print(f)
+
+# backprop
+
+ini = 1.0
+dnum = ini * invden
+dinvden = ini * num
+dden = -dinvden * (1.0 / den)**2
+dsigx = 1.0 * dden
+dx = sigx * (1 - sigx) * dsigx
+
+dxpysqr = dden * 1.0
+dxpy = 2 * xpy * dxpysqr
+dx += dxpy * 1.0
+dy = dxpy * 1.0
+
+dsigy = dnum * 1.0
+dy += sigy * (1 - sigy) * dsigy
+
+print(dy)
+print(dx)