diff --git a/proptest-regressions/math.txt b/proptest-regressions/math.txt
index 5f9e272..0edc464 100644
--- a/proptest-regressions/math.txt
+++ b/proptest-regressions/math.txt
@@ -7,3 +7,4 @@
 cc ea2a2598ee637946e47a8a744d25f76239671b82c5971a56b14ce5ee06838cb4 # shrinks to x = 4.8329699435311735, y = 9.38911339170414
 cc cf16a8d08e8ee8f7f3d3cfd60840e136ac51d130dffcd42db1a9a68d7e51f394 # shrinks to (x, y) = ([2.9394791070664547e110, 0.0], [inf, 0.0]), a = -2.4153502104628106e222
 cc 28897b64919482133f3885c3de51da0895409d23c9dd503a7b51a3e949bda307 # shrinks to (x1, x2, x3, y1, y2) = ([0.0], [0.0], [-4.0946726283401733e139], [0.0], [1.3157422010991668e73])
+cc acf6caef8a89a75ddab31ec3e391850723a625084df032aec2b650c2f95ba1fb # shrinks to (x, y) = ([0.0, 0.0, 0.0, 1.2271235629394547e205, 0.0, 0.0, -0.0, 0.0], [0.0, 0.0, 0.0, 7.121658452243713e81, 0.0, 0.0, 0.0, 0.0]), a = -6.261465657118442e-124
diff --git a/src/cpu_math.rs b/src/cpu_math.rs
index f335e5e..81cb489 100644
--- a/src/cpu_math.rs
+++ b/src/cpu_math.rs
@@ -115,10 +115,12 @@ impl<F: CpuLogpFunc> Math for CpuMath<F> {
     }
 
     fn array_all_finite_and_nonzero(&mut self, array: &Self::Array) -> bool {
-        array
-            .col_ref(0)
-            .iter()
-            .all(|&x| x.is_finite() & (x != 0f64))
+        self.arch.dispatch(|| {
+            array
+                .col_ref(0)
+                .iter()
+                .all(|&x| x.is_finite() & (x != 0f64))
+        })
     }
 
     fn array_mult(&mut self, array1: &Self::Array, array2: &Self::Array, dest: &mut Self::Array) {
@@ -152,16 +154,18 @@ impl<F: CpuLogpFunc> Math for CpuMath<F> {
         value: &Self::Array,
         diff_scale: f64, // 1 / self.count
     ) {
-        izip!(
-            mean.col_mut(0).iter_mut(),
-            variance.col_mut(0).iter_mut(),
-            value.col_ref(0)
-        )
-        .for_each(|(mean, mut var, x)| {
-            let diff = x - *mean;
-            *mean += diff * diff_scale;
-            *var += diff * diff;
-        });
+        self.arch.dispatch(|| {
+            izip!(
+                mean.col_mut(0).iter_mut(),
+                variance.col_mut(0).iter_mut(),
+                value.col_ref(0)
+            )
+            .for_each(|(mean, var, x)| {
+                let diff = x - *mean;
+                *mean += diff * diff_scale;
+                *var += diff * diff;
+            });
+        })
     }
 
     fn array_update_var_inv_std_draw_grad(
@@ -173,24 +177,26 @@ impl<F: CpuLogpFunc> Math for CpuMath<F> {
         fill_invalid: Option<f64>,
         clamp: (f64, f64),
     ) {
-        izip!(
-            variance_out.col_mut(0).iter_mut(),
-            inv_std.col_mut(0).iter_mut(),
-            draw_var.col_ref(0).iter(),
-            grad_var.col_ref(0).iter(),
-        )
-        .for_each(|(var_out, inv_std_out, &draw_var, &grad_var)| {
-            let val = (draw_var / grad_var).sqrt();
-            if (!val.is_finite()) | (val == 0f64) {
-                if let Some(fill_val) = fill_invalid {
-                    *var_out = fill_val;
-                    *inv_std_out = fill_val.recip().sqrt();
+        self.arch.dispatch(|| {
+            izip!(
+                variance_out.col_mut(0).iter_mut(),
+                inv_std.col_mut(0).iter_mut(),
+                draw_var.col_ref(0).iter(),
+                grad_var.col_ref(0).iter(),
+            )
+            .for_each(|(var_out, inv_std_out, &draw_var, &grad_var)| {
+                let val = (draw_var / grad_var).sqrt();
+                if (!val.is_finite()) | (val == 0f64) {
+                    if let Some(fill_val) = fill_invalid {
+                        *var_out = fill_val;
+                        *inv_std_out = fill_val.recip().sqrt();
+                    }
+                } else {
+                    let val = val.clamp(clamp.0, clamp.1);
+                    *var_out = val;
+                    *inv_std_out = val.recip().sqrt();
                 }
-            } else {
-                let val = val.clamp(clamp.0, clamp.1);
-                *var_out = val;
-                *inv_std_out = val.recip().sqrt();
-            }
+            });
         });
     }
 
@@ -202,16 +208,18 @@ impl<F: CpuLogpFunc> Math for CpuMath<F> {
         fill_invalid: f64,
         clamp: (f64, f64),
     ) {
-        izip!(
-            variance_out.col_mut(0).iter_mut(),
-            inv_std.col_mut(0).iter_mut(),
-            gradient.col_ref(0).iter(),
-        )
-        .for_each(|(var_out, inv_std_out, &grad_var)| {
-            let val = grad_var.abs().clamp(clamp.0, clamp.1).recip();
-            let val = if val.is_finite() { val } else { fill_invalid };
-            *var_out = val;
-            *inv_std_out = val.recip().sqrt();
+        self.arch.dispatch(|| {
+            izip!(
+                variance_out.col_mut(0).iter_mut(),
+                inv_std.col_mut(0).iter_mut(),
+                gradient.col_ref(0).iter(),
+            )
+            .for_each(|(var_out, inv_std_out, &grad_var)| {
+                let val = grad_var.abs().clamp(clamp.0, clamp.1).recip();
+                let val = if val.is_finite() { val } else { fill_invalid };
+                *var_out = val;
+                *inv_std_out = val.recip().sqrt();
+            });
         });
     }
 }
diff --git a/src/mass_matrix.rs b/src/mass_matrix.rs
index c6b89bf..f9878e6 100644
--- a/src/mass_matrix.rs
+++ b/src/mass_matrix.rs
@@ -1,6 +1,3 @@
-use itertools::izip;
-use multiversion::multiversion;
-
 use crate::{
     math_base::Math,
     nuts::Collector,
@@ -71,23 +68,6 @@ impl<M: Math> DiagMassMatrix<M> {
     }
 }
 
-#[multiversion(targets("x86_64+avx+avx2+fma", "arm+neon"))]
-fn update_diag(
-    variance_out: &mut [f64],
-    inv_std_out: &mut [f64],
-    new_variance: impl Iterator<Item = Option<f64>>,
-) {
-    izip!(variance_out, inv_std_out, new_variance).for_each(|(var, inv_std, x)| {
-        if let Some(x) = x {
-            assert!(x.is_finite(), "Illegal value on mass matrix: {}", x);
-            assert!(x > 0f64, "Illegal value on mass matrix: {}", x);
-            //assert!(*var != x, "No change in mass matrix from {} to {}", *var, x);
-            *var = x;
-            *inv_std = (1. / x).sqrt();
-        };
-    });
-}
-
 impl<M: Math> MassMatrix<M> for DiagMassMatrix<M> {
     fn update_velocity(&self, math: &mut M, state: &mut InnerState<M>) {
         math.array_mult(&self.variance, &state.p, &mut state.v);
diff --git a/src/math.rs b/src/math.rs
index dadd322..7161fde 100644
--- a/src/math.rs
+++ b/src/math.rs
@@ -373,7 +373,7 @@ mod tests {
             let mut y = y.clone();
             axpy(&x[..], &mut y[..], a);
             for ((&x, y), out) in x.iter().zip(orig).zip(y) {
-                assert_approx_eq(out, a * x + y);
+                assert_approx_eq(out, a.mul_add(x, y));
             }
         }
 
diff --git a/src/nuts.rs b/src/nuts.rs
index 4787068..0efc3bf 100644
--- a/src/nuts.rs
+++ b/src/nuts.rs
@@ -1069,7 +1069,7 @@ mod tests {
     fn to_arrow() {
         let ndim = 10;
         let func = NormalLogp::new(ndim, 3.);
-        let mut math = CpuMath::new(func);
+        let math = CpuMath::new(func);
 
         let settings = SamplerArgs::default();
         let mut rng = thread_rng();
diff --git a/src/state.rs b/src/state.rs
index 489301b..45e83d2 100644
--- a/src/state.rs
+++ b/src/state.rs
@@ -1,8 +1,7 @@
 use std::{
     cell::RefCell,
     fmt::Debug,
-    marker::PhantomData,
-    ops::{Deref, DerefMut},
+    ops::Deref,
     rc::{Rc, Weak},
 };
 
@@ -54,7 +53,6 @@ pub(crate) struct InnerState<M: Math> {
     pub(crate) idx_in_trajectory: i64,
     pub(crate) kinetic_energy: f64,
     pub(crate) potential_energy: f64,
-    _phantom_todo: PhantomData<M>,
 }
 
 pub(crate) struct InnerStateReusable<M: Math> {
@@ -74,7 +72,6 @@ impl<'pool, M: Math> InnerStateReusable<M> {
                 idx_in_trajectory: 0,
                 kinetic_energy: 0.,
                 potential_energy: 0.,
-                _phantom_todo: PhantomData::default(),
             },
             reuser: Rc::downgrade(&Rc::clone(&owner.storage)),
         }
@@ -225,7 +222,7 @@ mod tests {
     fn crate_pool() {
         let logp = NormalLogp::new(10, 0.2);
         let mut math = CpuMath::new(logp);
-        let mut pool = StatePool::new(&mut math, 10);
+        let pool = StatePool::new(&mut math, 10);
         let mut state = pool.new_state(&mut math);
         assert!(state.p.nrows() == 10);
         assert!(state.p.ncols() == 1);
@@ -241,7 +238,7 @@ mod tests {
         let dim = 10;
         let logp = NormalLogp::new(dim, 0.2);
         let mut math = CpuMath::new(logp);
-        let mut pool = StatePool::new(&mut math, 10);
+        let pool = StatePool::new(&mut math, 10);
         let a = pool.new_state(&mut math);
 
         assert_eq!(a.idx_in_trajectory, 0);