feat: implement inverse fast fourier transform (irfftn) function for …

…paddle frontend (#23526)

ivy/functional/frontends/paddle/fft.py

@@ -145,6 +145,58 @@ def irfft(x, n=None, axis=-1.0, norm="backward", name=None):
     return time_domain
 
 
+@with_supported_dtypes(
+    {"2.5.1 and below": ("complex64", "complex128")},
+    "paddle",
+)
+@to_ivy_arrays_and_back
+def irfftn(x, s=None, axes=None, norm="backward", name=None):
+    x = ivy.array(x)
+
+    if axes is None:
+        axes = list(range(len(x.shape)))
+
+    include_last_axis = len(x.shape) - 1 in axes
+
+    if s is None:
+        s = [
+            x.shape[axis] if axis != (len(x.shape) - 1) else 2 * (x.shape[axis] - 1)
+            for axis in axes
+        ]
+
+    real_result = x
+    remaining_axes = [axis for axis in axes if axis != (len(x.shape) - 1)]
+
+    if remaining_axes:
+        real_result = ivy.ifftn(
+            x,
+            s=[s[axes.index(axis)] for axis in remaining_axes],
+            axes=remaining_axes,
+            norm=norm,
+        )
+
+    if include_last_axis:
+        axis = len(x.shape) - 1
+        size = s[axes.index(axis)]
+        freq_domain = ivy.moveaxis(real_result, axis, -1)
+        slices = [slice(None)] * ivy.get_num_dims(freq_domain)
+        slices[-1] = slice(0, size // 2 + 1)
+        pos_freq_terms = freq_domain[tuple(slices)]
+        slices[-1] = slice(1, -1)
+        neg_freq_terms = ivy.conj(pos_freq_terms[tuple(slices)][..., ::-1])
+        combined_freq_terms = ivy.concat((pos_freq_terms, neg_freq_terms), axis=-1)
+        real_result = ivy.ifftn(combined_freq_terms, s=[size], axes=[-1], norm=norm)
+        real_result = ivy.moveaxis(real_result, -1, axis)
+
+    if ivy.is_complex_dtype(x.dtype):
+        output_dtype = "float32" if x.dtype == "complex64" else "float64"
+    else:
+        output_dtype = "float32"
+
+    result_t = ivy.astype(real_result, output_dtype)
+    return result_t
+
+
 @to_ivy_arrays_and_back
 def rfftfreq(n, d=1.0, dtype=None, name=None):
     dtype = ivy.default_dtype()

ivy_tests/test_ivy/test_frontends/test_paddle/test_fft.py

@@ -265,6 +265,43 @@ def test_paddle_irfft(
     )
 
 
+@handle_frontend_test(
+    fn_tree="paddle.fft.irfftn",
+    dtype_x_axis=helpers.dtype_values_axis(
+        available_dtypes=helpers.get_dtypes("complex"),
+        min_value=-10,
+        max_value=10,
+        min_num_dims=1,
+        max_num_dims=5,
+        min_dim_size=2,
+        max_dim_size=5,
+        valid_axis=True,
+        force_int_axis=True,
+    ),
+    norm=st.sampled_from(["backward", "ortho", "forward"]),
+)
+def test_paddle_irfftn(
+    dtype_x_axis,
+    norm,
+    frontend,
+    test_flags,
+    fn_tree,
+    backend_fw,
+):
+    input_dtypes, x, axis = dtype_x_axis
+    helpers.test_frontend_function(
+        input_dtypes=input_dtypes,
+        backend_to_test=backend_fw,
+        frontend=frontend,
+        test_flags=test_flags,
+        fn_tree=fn_tree,
+        x=x[0],
+        s=None,
+        axes=None,
+        norm=norm,
+    )
+
+
 @handle_frontend_test(
     fn_tree="paddle.fft.rfftfreq",
     n=st.integers(min_value=1, max_value=1000),