faster randmtzig_exprnd (separate unlikely branch + @inline)

Author: rfourquet

base/random.jl

@@ -984,20 +984,23 @@ randn(dims::Int...) = randn!(Array(Float64, dims...))
 randn(rng::MersenneTwister, dims::Dims) = randn!(rng, Array(Float64, dims))
 randn(rng::MersenneTwister, dims::Int...) = randn!(rng, Array(Float64, dims...))
 
-function randmtzig_exprnd(rng::MersenneTwister=GLOBAL_RNG)
+@inline function randmtzig_exprnd(rng::MersenneTwister=GLOBAL_RNG)
     @inbounds begin
-        while true
-            ri = rand_ui52(rng)
-            idx = ri & 0xFF
-            x = ri*we[idx+1]
-            if ri < ke[idx+1]
-                return x # 98.9% of the time we return here 1st try
-            elseif idx == 0
-                return ziggurat_exp_r - log(rand(rng))
-            elseif (fe[idx] - fe[idx+1])*rand(rng) + fe[idx+1] < exp(-x)
-                return x # return from the triangular area
-            end
-        end
+        ri = rand_ui52(rng)
+        idx = ri & 0xFF
+        x = ri*we[idx+1]
+        ri < ke[idx+1] && return x # 98.9% of the time we return here 1st try
+        return randmtzig_exprnd_unlikely(rng, idx, x)
+    end
+end
+
+function randmtzig_exprnd_unlikely(rng, idx, x)
+    @inbounds if idx == 0
+        return ziggurat_exp_r - log(rand(rng))
+    elseif (fe[idx] - fe[idx+1])*rand(rng) + fe[idx+1] < exp(-x)
+        return x # return from the triangular area
+    else
+        return randmtzig_exprnd(rng)
     end
 end