From 498e163814d8019587d231e3b7accf5273d3a07d Mon Sep 17 00:00:00 2001
From: Philipp Holl <pholl@europe.altair.com>
Date: Mon, 13 Jan 2025 17:57:12 +0100
Subject: [PATCH] Fix concat() for values without concat dim

---
 phiml/math/_magic_ops.py | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/phiml/math/_magic_ops.py b/phiml/math/_magic_ops.py
index 547310a..7825582 100644
--- a/phiml/math/_magic_ops.py
+++ b/phiml/math/_magic_ops.py
@@ -325,20 +325,22 @@ def concat(values: Sequence[PhiTreeNodeType], dim: Union[str, Shape], expand_val
     else:
         dim = auto(dim, channel).name
     # --- Filter 0-length values ---
-    values = [v for v in values if shape(v).get_size(dim) > 0]
+    shapes = [shape(v) for v in values]
+    values = [v for v, s in zip(values, shapes) if dim not in s or s.get_size(dim) > 0]
     if len(values) == 1:
         return values[0]
+    shapes = [s for s in shapes if dim not in s or s.get_size(dim) > 0]
     #  --- Add missing dimensions ---
     if expand_values:
-        all_dims = merge_shapes(*values, allow_varying_sizes=True)
+        all_dims = merge_shapes(*shapes, allow_varying_sizes=True)
         all_dims = all_dims.with_dim_size(dim, 1, keep_item_names=False)
-        values = [expand(v, all_dims.without(shape(v))) for v in values]
+        values = [expand(v, all_dims - s) for v, s in zip(values, shapes)]
     else:
-        for v in values:
-            assert dim in shape(v), f"concat dim '{dim}' must be present in the shapes of all values bot got value {type(v).__name__} with shape {shape(v)}"
+        for v, s in zip(values, shapes):
+            assert dim in s, f"concat dim '{dim}' must be present in the shapes of all values bot got value {type(v).__name__} with shape {s}"
         for v in values[1:]:
             assert set(non_batch(v).names) == set(non_batch(values[0]).names), f"Concatenated values must have the same non-batch dims but got {non_batch(values[0])} and {non_batch(v)}"
-        all_batch_dims = merge_shapes(*[shape(v).batch.without(dim) for v in values])
+        all_batch_dims = merge_shapes(*[s.batch - dim for s in shapes])
         values = [expand(v, all_batch_dims) for v in values]
     # --- First try __concat__ ---
     for v in values:
@@ -367,7 +369,7 @@ def concat(values: Sequence[PhiTreeNodeType], dim: Union[str, Shape], expand_val
         raise MagicNotImplemented(f"concat: No value implemented __concat__ and not all values were Sliceable along {dim}. values = {[type(v) for v in values]}")
     if len(unstacked) > 8:
         warnings.warn(f"concat() default implementation is slow on large dims ({dim}={len(unstacked)}). Please implement __concat__()", RuntimeWarning, stacklevel=2)
-    dim = shape(values[0])[dim].with_size(None)
+    dim = shapes[0][dim].with_size(None)
     try:
         return stack(unstacked, dim, **kwargs)
     except MagicNotImplemented: