The elementwise Kullback-Leibler divergence, \(x\log(x/y) - x + y\).

kl_div(x, y)

Arguments

x

An Expression, vector, or matrix.

y

An Expression, vector, or matrix.

Value

An Expression representing the KL-divergence of the input.

Examples

n <- 5
alpha <- seq(10, n-1+10)/n
beta <- seq(10, n-1+10)/n
P_tot <- 0.5
W_tot <- 1.0

P <- Variable(n)
W <- Variable(n)
R <- kl_div(alpha*W, alpha*(W + beta*P)) - alpha*beta*P
obj <- sum(R)
constr <- list(P >= 0, W >= 0, sum(P) == P_tot, sum(W) == W_tot)
prob <- Problem(Minimize(obj), constr)
result <- solve(prob)

result$value
#> [1] -2.451312
result$getValue(P)
#>              [,1]
#> [1,] 1.151280e-09
#> [2,] 1.707969e-09
#> [3,] 2.756063e-09
#> [4,] 5.787514e-09
#> [5,] 5.000000e-01
result$getValue(W)
#>              [,1]
#> [1,] 3.090819e-09
#> [2,] 3.954698e-09
#> [3,] 5.908461e-09
#> [4,] 1.192709e-08
#> [5,] 1.000000e+00