diff --git a/src/weight_matrix.rs b/src/weight_matrix.rs
index f2ba33d..233ec85 100644
--- a/src/weight_matrix.rs
+++ b/src/weight_matrix.rs
@@ -31,25 +31,19 @@ impl<T: WeightNum> Weights for WeightMatrix<T> {
     fn add_row(&mut self, row: usize, val: T) {
         self.c
             .row_mut(row)
-            .mapv_inplace(|cur| if cur.is_disallowed() { cur } else { cur + val });
+            .mapv_inplace(|cur| if cur.is_valid() { cur + val } else { cur });
     }
 
     // Subtract `val` from every element in column `col`.
     fn sub_column(&mut self, col: usize, val: T) {
-        self.c.column_mut(col).mapv_inplace(
-            |cur| {
-                if cur.is_disallowed() {
-                    cur
-                } else {
-                    cur - val
-                }
-            },
-        );
+        self.c
+            .column_mut(col)
+            .mapv_inplace(|cur| if cur.is_valid() { cur - val } else { cur });
     }
 
     fn is_solvable(&self) -> bool {
         for row in 0..self.n() {
-            if self.c.row(row).iter().all(|c| c.is_disallowed()) {
+            if self.c.row(row).iter().all(|c| !c.is_valid()) {
                 return false;
             }
         }
@@ -76,7 +70,7 @@ impl<T: WeightNum> WeightMatrix<T> {
         let row_slice = self.c.row(row);
         let mut min = row_slice[0];
         for &val in row_slice.iter().skip(1) {
-            if !val.is_disallowed() && val < min {
+            if val.is_valid() && val < min {
                 min = val;
             }
         }
@@ -87,7 +81,7 @@ impl<T: WeightNum> WeightMatrix<T> {
     fn sub_row(&mut self, row: usize, val: T) {
         self.c
             .row_mut(row)
-            .mapv_inplace(|cur| if cur.is_disallowed() { cur } else { cur - val });
+            .mapv_inplace(|cur| if cur.is_valid() { cur - val } else { cur });
     }
 
     pub fn as_slice(&self) -> &[T] {
diff --git a/src/weight_num.rs b/src/weight_num.rs
index 7aef23c..57b37ef 100644
--- a/src/weight_num.rs
+++ b/src/weight_num.rs
@@ -3,8 +3,8 @@ use std::{f32, f64};
 
 pub trait WeightNum: PartialOrd + Copy + Sub<Output = Self> + Add<Output = Self> {
     fn is_zero(&self) -> bool;
-    fn is_disallowed(&self) -> bool {
-        false
+    fn is_valid(&self) -> bool {
+        true
     }
 }
 
@@ -84,8 +84,9 @@ impl WeightNum for f64 {
         *self == 0.0
     }
 
-    fn is_disallowed(&self) -> bool {
-        *self == f64::INFINITY
+    #[inline(always)]
+    fn is_valid(&self) -> bool {
+        self.is_finite()
     }
 }
 
@@ -95,7 +96,8 @@ impl WeightNum for f32 {
         *self == 0.0
     }
 
-    fn is_disallowed(&self) -> bool {
-        *self == f32::INFINITY
+    #[inline(always)]
+    fn is_valid(&self) -> bool {
+        self.is_finite()
     }
 }