Add is_nan and contains_nan tensor ops (#2088)

* Add is_nan and contains_nan tensor ops

* Enable nan test for burn-candle

* Disabling tests due to #2089

burn-book/src/building-blocks/tensor.md

@@ -190,6 +190,7 @@ Those operations are available for numeric tensor kinds: `Float` and `Int`.
 | `tensor.clamp(min, max)`                                        | `torch.clamp(tensor, min=min, max=max)`        |
 | `tensor.clamp_max(max)`                                         | `torch.clamp(tensor, max=max)`                 |
 | `tensor.clamp_min(min)`                                         | `torch.clamp(tensor, min=min)`                 |
+| `tensor.contains_nan()`                                         | N/A                                            |
 | `tensor.div(other)` or `tensor / other`                         | `tensor / other`                               |
 | `tensor.div_scalar(scalar)` or `tensor / scalar`                | `tensor / scalar`                              |
 | `tensor.equal_elem(other)`                                      | `tensor.eq(other)`                             |
@@ -199,6 +200,7 @@ Those operations are available for numeric tensor kinds: `Float` and `Int`.
 | `tensor.greater_equal(other)`                                   | `tensor.ge(other)`                             |
 | `tensor.greater_equal_elem(scalar)`                             | `tensor.ge(scalar)`                            |
 | `tensor.is_close(other, atol, rtol)`                            | `torch.isclose(tensor, other, atol, rtol)`     |
+| `tensor.is_nan()`                                               | `torch.isnan(tensor)`                          |
 | `tensor.lower(other)`                                           | `tensor.lt(other)`                             |
 | `tensor.lower_elem(scalar)`                                     | `tensor.lt(scalar)`                            |
 | `tensor.lower_equal(other)`                                     | `tensor.le(other)`                             |
@@ -304,12 +306,13 @@ Those operations are only available for `Bool` tensors.
 
 ### Quantization Operations
 
-Those operations are only available for `Float` tensors on backends that implement quantization strategies.
+Those operations are only available for `Float` tensors on backends that implement quantization
+strategies.
 
-| Burn API                             | PyTorch Equivalent              |
-| ------------------------------------ | ------------------------------- |
-| `tensor.quantize(scheme, qparams)`   | N/A                             |
-| `tensor.dequantize()`                | N/A                             |
+| Burn API                           | PyTorch Equivalent |
+| ---------------------------------- | ------------------ |
+| `tensor.quantize(scheme, qparams)` | N/A                |
+| `tensor.dequantize()`              | N/A                |
 
 ## Activation Functions
 

crates/burn-candle/src/lib.rs

@@ -87,6 +87,7 @@ mod tests {
     burn_tensor::testgen_flip!();
     burn_tensor::testgen_argwhere_nonzero!();
     burn_tensor::testgen_sign!();
+    burn_tensor::testgen_nan!();
 
     // TODO: https://github.com/tracel-ai/burn/issues/1237
     //

crates/burn-tensor/src/tensor/api/numeric.rs

@@ -778,6 +778,32 @@ where
         // Assign the original tensor data to the appropriate slice of the padded tensor
         padded_tensor.slice_assign(ranges, self)
     }
+
+    /// Returns a new tensor with boolean elements indicating whether each element of the input is NaN.
+    ///
+    /// # Returns
+    ///
+    /// A boolean tensor where `true` indicates NaN and `false` indicates a non-NaN value.
+    pub fn is_nan(&self) -> Tensor<B, D, Bool> {
+        // Check if the input tensor is NaN by comparing it to itself
+        // NaN is the only value that is not equal to itself
+        K::not_equal(self.primitive.clone(), self.primitive.clone())
+    }
+
+    /// Checks if the tensor contains any NaN values.
+    ///
+    /// # Returns
+    ///
+    /// A boolean tensor with a single element indicating whether the tensor contains any NaN values.
+    pub fn contains_nan(&self) -> Tensor<B, 1, Bool> {
+        // Summing the tensor will result in NaN if the tensor contains any NaN values
+        // This is faster than checking each element individually
+        // because it rolls up the NaN values into a single value
+        let sum = K::sum(self.primitive.clone());
+
+        // Check if the sum is NaN by comparing it to itself
+        K::not_equal(sum.clone(), sum)
+    }
 }
 
 impl<B, K> Tensor<B, 2, K>

crates/burn-tensor/src/tests/mod.rs

@@ -103,6 +103,7 @@ macro_rules! testgen_all {
         burn_tensor::testgen_topk!();
         burn_tensor::testgen_remainder!();
         burn_tensor::testgen_cartesian_grid!();
+        burn_tensor::testgen_nan!();
 
         // test stats
         burn_tensor::testgen_var!();

crates/burn-tensor/src/tests/ops/mod.rs

@@ -34,6 +34,7 @@ mod matmul;
 mod maxmin;
 mod movedim;
 mod mul;
+mod nan;
 mod narrow;
 mod neg;
 mod one_hot;

crates/burn-tensor/src/tests/ops/nan.rs

@@ -0,0 +1,31 @@
+#[burn_tensor_testgen::testgen(nan)]
+mod tests {
+    use super::*;
+    use burn_tensor::{Int, Tensor, TensorData};
+
+    #[test]
+    #[ignore = "https://github.com/tracel-ai/burn/issues/2089"]
+    fn is_nan() {
+        let no_nan = TestTensor::<2>::from([[0.0, 1.0, 2.0], [3.0, 4.0, 5.0]]);
+        let no_nan_expected =
+            TestTensorBool::<2>::from([[false, false, false], [false, false, false]]);
+
+        let with_nan = TestTensor::<2>::from([[0.0, f32::NAN, 2.0], [f32::NAN, 4.0, 5.0]]);
+        let with_nan_expected =
+            TestTensorBool::<2>::from([[false, true, false], [true, false, false]]);
+
+        assert_eq!(no_nan_expected.into_data(), no_nan.is_nan().into_data());
+
+        assert_eq!(with_nan_expected.into_data(), with_nan.is_nan().into_data());
+    }
+
+    #[test]
+    #[ignore = "https://github.com/tracel-ai/burn/issues/2089"]
+    fn contains_nan() {
+        let no_nan = TestTensor::<2>::from([[0.0, 1.0, 2.0], [3.0, 4.0, 5.0]]);
+        assert!(!no_nan.contains_nan().into_scalar());
+
+        let with_nan = TestTensor::<2>::from([[0.0, f32::NAN, 2.0], [3.0, 4.0, 5.0]]);
+        assert!(with_nan.contains_nan().into_scalar());
+    }
+}