diff --git a/src/linalg/exp.rs b/src/linalg/exp.rs
index e07ddd2f..86bd81a7 100644
--- a/src/linalg/exp.rs
+++ b/src/linalg/exp.rs
@@ -66,87 +66,78 @@ where
         }
     }
 
-    fn a2(&self) -> &MatrixN<N, D> {
+    fn calc_a2(&mut self) {
         if self.a2.is_none() {
-            let ap = &self.a2 as *const Option<MatrixN<N, D>> as *mut Option<MatrixN<N, D>>;
-            unsafe {
-                *ap = Some(&self.a * &self.a);
-            }
+            self.a2 = Some(&self.a * &self.a);
         }
-        self.a2.as_ref().unwrap()
     }
 
-    fn a4(&self) -> &MatrixN<N, D> {
+    fn calc_a4(&mut self) {
         if self.a4.is_none() {
-            let ap = &self.a4 as *const Option<MatrixN<N, D>> as *mut Option<MatrixN<N, D>>;
-            let a2 = self.a2();
-            unsafe {
-                *ap = Some(a2 * a2);
-            }
+            self.calc_a2();
+            let a2 = self.a2.as_ref().unwrap();
+            self.a4 = Some(a2 * a2);
         }
-        self.a4.as_ref().unwrap()
     }
 
-    fn a6(&self) -> &MatrixN<N, D> {
+    fn calc_a6(&mut self) {
         if self.a6.is_none() {
-            let a2 = self.a2();
-            let a4 = self.a4();
-            let ap = &self.a6 as *const Option<MatrixN<N, D>> as *mut Option<MatrixN<N, D>>;
-            unsafe {
-                *ap = Some(a4 * a2);
-            }
+            self.calc_a2();
+            self.calc_a4();
+            let a2 = self.a2.as_ref().unwrap();
+            let a4 = self.a4.as_ref().unwrap();
+            self.a6 = Some(a4 * a2);
         }
-        self.a6.as_ref().unwrap()
     }
 
-    fn a8(&self) -> &MatrixN<N, D> {
+    fn calc_a8(&mut self) {
         if self.a8.is_none() {
-            let a2 = self.a2();
-            let a6 = self.a6();
-            let ap = &self.a8 as *const Option<MatrixN<N, D>> as *mut Option<MatrixN<N, D>>;
-            unsafe {
-                *ap = Some(a6 * a2);
-            }
+            self.calc_a2();
+            self.calc_a6();
+            let a2 = self.a2.as_ref().unwrap();
+            let a6 = self.a6.as_ref().unwrap();
+            self.a8 = Some(a6 * a2);
         }
-        self.a8.as_ref().unwrap()
     }
 
-    fn a10(&mut self) -> &MatrixN<N, D> {
+    fn calc_a10(&mut self) {
         if self.a10.is_none() {
-            let a4 = self.a4();
-            let a6 = self.a6();
-            let ap = &self.a10 as *const Option<MatrixN<N, D>> as *mut Option<MatrixN<N, D>>;
-            unsafe {
-                *ap = Some(a6 * a4);
-            }
+            self.calc_a4();
+            self.calc_a6();
+            let a4 = self.a4.as_ref().unwrap();
+            let a6 = self.a6.as_ref().unwrap();
+            self.a10 = Some(a6 * a4);
         }
-        self.a10.as_ref().unwrap()
     }
 
     fn d4_tight(&mut self) -> N {
         if self.d4_exact.is_none() {
-            self.d4_exact = Some(one_norm(self.a4()).powf(convert(0.25)));
+            self.calc_a4();
+            self.d4_exact = Some(one_norm(self.a4.as_ref().unwrap()).powf(convert(0.25)));
         }
         self.d4_exact.unwrap()
     }
 
     fn d6_tight(&mut self) -> N {
         if self.d6_exact.is_none() {
-            self.d6_exact = Some(one_norm(self.a6()).powf(convert(1.0 / 6.0)));
+            self.calc_a6();
+            self.d6_exact = Some(one_norm(self.a6.as_ref().unwrap()).powf(convert(1.0 / 6.0)));
         }
         self.d6_exact.unwrap()
     }
 
     fn d8_tight(&mut self) -> N {
         if self.d8_exact.is_none() {
-            self.d8_exact = Some(one_norm(self.a8()).powf(convert(1.0 / 8.0)));
+            self.calc_a8();
+            self.d8_exact = Some(one_norm(self.a8.as_ref().unwrap()).powf(convert(1.0 / 8.0)));
         }
         self.d8_exact.unwrap()
     }
 
     fn d10_tight(&mut self) -> N {
         if self.d10_exact.is_none() {
-            self.d10_exact = Some(one_norm(self.a10()).powf(convert(1.0 / 10.0)));
+            self.calc_a10();
+            self.d10_exact = Some(one_norm(self.a10.as_ref().unwrap()).powf(convert(1.0 / 10.0)));
         }
         self.d10_exact.unwrap()
     }
@@ -161,7 +152,8 @@ where
         }
 
         if self.d4_approx.is_none() {
-            self.d4_approx = Some(one_norm(self.a4()).powf(convert(0.25)));
+            self.calc_a4();
+            self.d4_approx = Some(one_norm(self.a4.as_ref().unwrap()).powf(convert(0.25)));
         }
 
         self.d4_approx.unwrap()
@@ -177,7 +169,8 @@ where
         }
 
         if self.d6_approx.is_none() {
-            self.d6_approx = Some(one_norm(self.a6()).powf(convert(1.0 / 6.0)));
+            self.calc_a6();
+            self.d6_approx = Some(one_norm(self.a6.as_ref().unwrap()).powf(convert(1.0 / 6.0)));
         }
 
         self.d6_approx.unwrap()
@@ -193,7 +186,8 @@ where
         }
 
         if self.d8_approx.is_none() {
-            self.d8_approx = Some(one_norm(self.a8()).powf(convert(1.0 / 8.0)));
+            self.calc_a8();
+            self.d8_approx = Some(one_norm(self.a8.as_ref().unwrap()).powf(convert(1.0 / 8.0)));
         }
 
         self.d8_approx.unwrap()
@@ -209,7 +203,8 @@ where
         }
 
         if self.d10_approx.is_none() {
-            self.d10_approx = Some(one_norm(self.a10()).powf(convert(1.0 / 10.0)));
+            self.calc_a10();
+            self.d10_approx = Some(one_norm(self.a10.as_ref().unwrap()).powf(convert(1.0 / 10.0)));
         }
 
         self.d10_approx.unwrap()
@@ -217,8 +212,10 @@ where
 
     fn pade3(&mut self) -> (MatrixN<N, D>, MatrixN<N, D>) {
         let b: [N; 4] = [convert(120.0), convert(60.0), convert(12.0), convert(1.0)];
-        let u = &self.a * (self.a2() * b[3] + &self.ident * b[1]);
-        let v = self.a2() * b[2] + &self.ident * b[0];
+        self.calc_a2();
+        let a2 = self.a2.as_ref().unwrap();
+        let u = &self.a * (a2 * b[3] + &self.ident * b[1]);
+        let v = a2 * b[2] + &self.ident * b[0];
         (u, v)
     }
 
@@ -231,8 +228,15 @@ where
             convert(30.0),
             convert(1.0),
         ];
-        let u = &self.a * (self.a4() * b[5] + self.a2() * b[3] + &self.ident * b[1]);
-        let v = self.a4() * b[4] + self.a2() * b[2] + &self.ident * b[0];
+        self.calc_a2();
+        self.calc_a6();
+        let u = &self.a
+            * (self.a4.as_ref().unwrap() * b[5]
+                + self.a2.as_ref().unwrap() * b[3]
+                + &self.ident * b[1]);
+        let v = self.a4.as_ref().unwrap() * b[4]
+            + self.a2.as_ref().unwrap() * b[2]
+            + &self.ident * b[0];
         (u, v)
     }
 
@@ -247,9 +251,18 @@ where
             convert(56.0),
             convert(1.0),
         ];
-        let u =
-            &self.a * (self.a6() * b[7] + self.a4() * b[5] + self.a2() * b[3] + &self.ident * b[1]);
-        let v = self.a6() * b[6] + self.a4() * b[4] + self.a2() * b[2] + &self.ident * b[0];
+        self.calc_a2();
+        self.calc_a4();
+        self.calc_a6();
+        let u = &self.a
+            * (self.a6.as_ref().unwrap() * b[7]
+                + self.a4.as_ref().unwrap() * b[5]
+                + self.a2.as_ref().unwrap() * b[3]
+                + &self.ident * b[1]);
+        let v = self.a6.as_ref().unwrap() * b[6]
+            + self.a4.as_ref().unwrap() * b[4]
+            + self.a2.as_ref().unwrap() * b[2]
+            + &self.ident * b[0];
         (u, v)
     }
 
@@ -266,16 +279,20 @@ where
             convert(90.0),
             convert(1.0),
         ];
+        self.calc_a2();
+        self.calc_a4();
+        self.calc_a6();
+        self.calc_a8();
         let u = &self.a
-            * (self.a8() * b[9]
-                + self.a6() * b[7]
-                + self.a4() * b[5]
-                + self.a2() * b[3]
+            * (self.a8.as_ref().unwrap() * b[9]
+                + self.a6.as_ref().unwrap() * b[7]
+                + self.a4.as_ref().unwrap() * b[5]
+                + self.a2.as_ref().unwrap() * b[3]
                 + &self.ident * b[1]);
-        let v = self.a8() * b[8]
-            + self.a6() * b[6]
-            + self.a4() * b[4]
-            + self.a2() * b[2]
+        let v = self.a8.as_ref().unwrap() * b[8]
+            + self.a6.as_ref().unwrap() * b[6]
+            + self.a4.as_ref().unwrap() * b[4]
+            + self.a2.as_ref().unwrap() * b[2]
             + &self.ident * b[0];
         (u, v)
     }
@@ -300,9 +317,12 @@ where
         let s = s as f64;
 
         let mb = &self.a * convert::<f64, N>(2.0_f64.powf(-s));
-        let mb2 = self.a2() * convert::<f64, N>(2.0_f64.powf(-2.0 * s));
-        let mb4 = self.a4() * convert::<f64, N>(2.0.powf(-4.0 * s));
-        let mb6 = self.a6() * convert::<f64, N>(2.0.powf(-6.0 * s));
+        self.calc_a2();
+        self.calc_a4();
+        self.calc_a6();
+        let mb2 = self.a2.as_ref().unwrap() * convert::<f64, N>(2.0_f64.powf(-2.0 * s));
+        let mb4 = self.a4.as_ref().unwrap() * convert::<f64, N>(2.0.powf(-4.0 * s));
+        let mb6 = self.a6.as_ref().unwrap() * convert::<f64, N>(2.0.powf(-6.0 * s));
 
         let u2 = &mb6 * (&mb6 * b[13] + &mb4 * b[11] + &mb2 * b[9]);
         let u = &mb * (&u2 + &mb6 * b[7] + &mb4 * b[5] + &mb2 * b[3] + &self.ident * b[1]);