diff --git a/wonnx/src/compiler.rs b/wonnx/src/compiler.rs
index bed2b865..ba757c20 100644
--- a/wonnx/src/compiler.rs
+++ b/wonnx/src/compiler.rs
@@ -2,7 +2,7 @@
 use crate::utils::{
     ceil, AttributeNotFoundError, DataTypeError, MultiType, NodeAttributes, ScalarType, Shape,
 };
-use num::integer::gcd;
+use num::integer::{gcd, Roots};
 use tera::{Context, Tera};
 use thiserror::Error;
 
@@ -792,10 +792,13 @@ pub fn compile(
             }
             context.insert("cum_len", &input_cumulative_len);
 
+            let root = output_lengths[0].sqrt() + 1;
+            let per_dim = ceil(root, 16) + 1;
+
             NodeTemplate {
                 scalar_type: agreed_type(input_shapes, output_shapes)?,
                 template: "matrix/concat.wgsl",
-                threads: (ceil(output_lengths[0], 256) as u32, 1, 1),
+                threads: (per_dim as u32, per_dim as u32, 1),
             }
         }
         op @ ("MaxPool" | "AveragePool" | "Conv" | "ConvRelu" | "ConvLeakyRelu" | "ConvMish"
diff --git a/wonnx/templates/matrix/concat.wgsl b/wonnx/templates/matrix/concat.wgsl
index 76872cf7..4c282723 100644
--- a/wonnx/templates/matrix/concat.wgsl
+++ b/wonnx/templates/matrix/concat.wgsl
@@ -12,19 +12,24 @@ var<storage, read> input_{{ loop.index0 }}: Array;
 @group({{ binding_len  / 4 | int }}) @binding({{ binding_len % 4 }})
 var<storage, read_write> output_0: Array;
 
-@compute @workgroup_size(256, 1, 1)
-fn main(@builtin(global_invocation_id) global_id: vec3<u32>) {
+@compute @workgroup_size(16, 16, 1)
+fn main(@builtin(global_invocation_id) global_id: vec3<u32>, @builtin(num_workgroups) num_workgroups: vec3<u32>) {
 	let gidx = global_id.x;
+        let gidy = global_id.y;
+
+        let nx = num_workgroups.x;
+
+        let actual_idx = gidx + gidy * nx;
 	
 	{% for input in i_lens %}
 		{% if loop.first %}
-			if (gidx < {{ i_lens[0] }}u) {
-				output_0.data[gidx] = input_0.data[gidx];
+			if (actual_idx < {{ i_lens[0] }}u) {
+				output_0.data[actual_idx] = input_0.data[actual_idx];
 			}
 
 		{% else %}
-			if ((gidx >= {{ cum_len | nth(n=loop.index0 -1) }}u) && (gidx < {{ cum_len | nth(n=loop.index0)}}u)) {
-				output_0.data[gidx] = input_{{ loop.index0 }}.data[gidx - {{ cum_len | nth(n=loop.index0 -1) }}u];
+			if ((actual_idx >= {{ cum_len | nth(n=loop.index0 -1) }}u) && (actual_idx < {{ cum_len | nth(n=loop.index0)}}u)) {
+				output_0.data[actual_idx] = input_{{ loop.index0 }}.data[actual_idx - {{ cum_len | nth(n=loop.index0 -1) }}u];
 			}
 			
 		{% endif %}
diff --git a/wonnx/tests/concat.rs b/wonnx/tests/concat.rs
new file mode 100644
index 00000000..980ad039
--- /dev/null
+++ b/wonnx/tests/concat.rs
@@ -0,0 +1,80 @@
+use std::{collections::HashMap, convert::TryInto};
+use wonnx::utils::{graph, model, node, tensor};
+mod common;
+
+#[test]
+fn test_concat() {
+    let n: usize = 16;
+
+    let xdata: Vec<f32> = (0..n).map(|x| x as f32).collect();
+    let mut ydata: Vec<f32> = (n..2 * n).map(|x| x as f32).collect();
+    let input_dims = vec![n as i64];
+    let output_dims = vec![(n * 2) as i64];
+
+    let input_data = HashMap::from([
+        ("X".into(), xdata.as_slice().into()),
+        ("Y".into(), ydata.as_slice().into()),
+    ]);
+
+    let model = model(graph(
+        vec![tensor("X", &input_dims), tensor("Y", &input_dims)],
+        vec![tensor("Z", &output_dims)],
+        vec![],
+        vec![],
+        vec![node(vec!["X", "Y"], vec!["Z"], "a", "Concat", vec![])],
+    ));
+
+    let session =
+        pollster::block_on(wonnx::Session::from_model(model)).expect("Session did not create");
+
+    let result = pollster::block_on(session.run(&input_data)).unwrap();
+
+    let mut expected_result = xdata.clone();
+    expected_result.append(&mut ydata);
+
+    common::assert_eq_vector((&result["Z"]).try_into().unwrap(), &expected_result);
+}
+
+#[test]
+fn test_concat4() {
+    let n: usize = 13;
+
+    let xdata: Vec<f32> = (0..n).map(|x| x as f32).collect();
+    let mut ydata: Vec<f32> = (n..2 * n).map(|x| x as f32).collect();
+    let mut zdata: Vec<f32> = (n * 2..3 * n).map(|x| x as f32).collect();
+    let mut wdata: Vec<f32> = (n * 3..4 * n).map(|x| x as f32).collect();
+    let input_dims = vec![n as i64];
+    let output_dims = vec![(n * 4) as i64];
+
+    let input_data = HashMap::from([
+        ("X".into(), xdata.as_slice().into()),
+        ("Y".into(), ydata.as_slice().into()),
+        ("Z".into(), zdata.as_slice().into()),
+        ("W".into(), wdata.as_slice().into()),
+    ]);
+
+    let model = model(graph(
+        vec![
+            tensor("X", &input_dims),
+            tensor("Y", &input_dims),
+            tensor("Z", &input_dims),
+            tensor("W", &input_dims),
+        ],
+        vec![tensor("O", &output_dims)],
+        vec![],
+        vec![],
+        vec![node(vec!["X", "Y", "Z", "W"], vec!["O"], "a", "Concat", vec![])],
+    ));
+
+    let session =
+        pollster::block_on(wonnx::Session::from_model(model)).expect("Session did not create");
+
+    let result = pollster::block_on(session.run(&input_data)).unwrap();
+
+    let mut expected_result = xdata.clone();
+    expected_result.append(&mut ydata);
+    expected_result.append(&mut zdata);
+    expected_result.append(&mut wdata);
+
+    common::assert_eq_vector((&result["O"]).try_into().unwrap(), &expected_result);
+}