diff --git a/nn.lua b/nn.lua
index 82dea0b..3faef88 100644
--- a/nn.lua
+++ b/nn.lua
@@ -187,6 +187,31 @@ local function cache(bs, shape)
     return zeros(fullshape)
 end
 
+local function dot_mv(mat, vec, out)
+    -- treats matrix as a matrix.
+    -- treats vec as a column vector, flattened.
+    assert(#mat.shape == 2)
+    local d0, d1 = unpack(mat.shape)
+    assert(d1 == #vec)
+
+    local out_shape = {d0}
+    if out == nil then
+        out = zeros(out_shape)
+    else
+        assert(d0 == #out, "given output is the wrong size")
+    end
+
+    for i=1, d0 do
+        local sum = 0
+        for j=1, d1 do
+            sum = sum + mat[(i - 1) * d1 + j] * vec[j]
+        end
+        out[i] = sum
+    end
+
+    return out
+end
+
 local function dot(a, b, ax_a, ax_b, out)
     ax_a = ax_a or #a.shape - 0
     ax_b = ax_b or #b.shape - 1
@@ -806,6 +831,7 @@ return {
     reshape = reshape,
     pp = pp,
     ppi = ppi,
+    dot_mv = dot_mv,
     dot = dot,
     traverse = traverse,
     traverse_all = traverse_all,
diff --git a/xnes.lua b/xnes.lua
index cc2c942..cc33599 100644
--- a/xnes.lua
+++ b/xnes.lua
@@ -16,6 +16,7 @@ local unpack = table.unpack or unpack
 local Base = require "Base"
 
 local nn = require "nn"
+local dot_mv = nn.dot_mv
 local normal = nn.normal
 local zeros = nn.zeros
 
@@ -24,31 +25,6 @@ local argsort = util.argsort
 
 local Xnes = Base:extend()
 
-local function dot_mv(mat, vec, out)
-    -- treats matrix as a matrix.
-    -- treats vec as a column vector, flattened.
-    assert(#mat.shape == 2)
-    local d0, d1 = unpack(mat.shape)
-    assert(d1 == #vec)
-
-    local out_shape = {d0}
-    if out == nil then
-        out = zeros(out_shape)
-    else
-        assert(d0 == #out, "given output is the wrong size")
-    end
-
-    for i=1, d0 do
-        local sum = 0
-        for j=1, d1 do
-            sum = sum + mat[(i - 1) * d1 + j] * vec[j]
-        end
-        out[i] = sum
-    end
-
-    return out
-end
-
 local function make_utility(popsize, out)
     local utility = out or {}
     local temp = log(popsize / 2 + 1)
@@ -230,7 +206,6 @@ function Xnes:tell(scored, noise)
 end
 
 return {
-    dot_mv = dot_mv,
     make_utility = make_utility,
     make_covars = make_covars,