gen_identity_weights: Change --mix to 50-50 blend

Updates --mix mode to use 50-50 weighting to avoid overflow:
- Before: p0+p4, p1+p5, p2+p6, p3+p7
- After: 0.5*p0+0.5*p4, 0.5*p1+0.5*p5, etc

Prevents saturation when blending input with static features.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 11 insertions, 11 deletions

diff --git a/training/gen_identity_weights.py b/training/gen_identity_weights.py
index 0d79593..5756e67 100755
--- a/training/gen_identity_weights.py
+++ b/training/gen_identity_weights.py
@@ -4,8 +4,8 @@
 Creates trivial .bin with 1 layer, 1×1 kernel, identity passthrough.
 Output Ch{0,1,2,3} = Input Ch{0,1,2,3} (ignores static features).
 
-With --mix: Output Ch{i} = Input Ch{i} + Input Ch{i+4}
-  (p0+p4, p1+p5, p2+p6, p3+p7)
+With --mix: Output Ch{i} = 0.5*Input Ch{i} + 0.5*Input Ch{i+4}
+  (50-50 blend, avoids overflow)
 
 With --p47: Output Ch{i} = Input Ch{i+4} (static features only)
   (p4→ch0, p5→ch1, p6→ch2, p7→ch3)
@@ -25,7 +25,7 @@ from pathlib import Path
 def generate_identity_weights(output_path, kernel_size=1, mip_level=0, mix=False, p47=False):
     """Generate identity weights: output = input (ignores static features).
 
-    If mix=True, adds p4→p0, p5→p1, p6→p2, p7→p3 (blends input with static).
+    If mix=True, 50-50 blend: 0.5*p0+0.5*p4, 0.5*p1+0.5*p5, etc (avoids overflow).
     If p47=True, transfers p4→p0, p5→p1, p6→p2, p7→p3 (static features only).
 
     Binary format:
@@ -63,16 +63,16 @@ def generate_identity_weights(output_path, kernel_size=1, mip_level=0, mix=False
         # p47 mode: p4→ch0, p5→ch1, p6→ch2, p7→ch3 (static features only)
         for i in range(out_channels):
             weights[i, i + 4, center, center] = 1.0
+    elif mix:
+        # Mix mode: 50-50 blend to avoid overflow
+        for i in range(out_channels):
+            weights[i, i, center, center] = 0.5       # 0.5*p{i}
+            weights[i, i + 4, center, center] = 0.5   # 0.5*p{i+4}
     else:
-        # Set diagonal to 1.0 (output ch i = input ch i)
+        # Identity: output ch i = input ch i
         for i in range(out_channels):
             weights[i, i, center, center] = 1.0
 
-        # If mix, add p4→p0, p5→p1, p6→p2, p7→p3
-        if mix:
-            for i in range(out_channels):
-                weights[i, i + 4, center, center] = 1.0
-
     # Flatten
     weights_flat = weights.flatten()
     weight_count = len(weights_flat)
@@ -84,7 +84,7 @@ def generate_identity_weights(output_path, kernel_size=1, mip_level=0, mix=False
     print(f"  Weights: {weight_count}")
     print(f"  Mip level: {mip_level}")
     if mix:
-        print(f"  Mode: p0+p4, p1+p5, p2+p6, p3+p7")
+        print(f"  Mode: 0.5*p0+0.5*p4, 0.5*p1+0.5*p5, 0.5*p2+0.5*p6, 0.5*p3+0.5*p7")
     elif p47:
         print(f"  Mode: p4→ch0, p5→ch1, p6→ch2, p7→ch3")
 
@@ -150,7 +150,7 @@ def main():
     parser.add_argument('--mip-level', type=int, default=0,
                        help='Mip level for p0-p3 features (default: 0)')
     parser.add_argument('--mix', action='store_true',
-                       help='Mix mode: p0+p4, p1+p5, p2+p6, p3+p7')
+                       help='Mix mode: 50-50 blend of p0-p3 and p4-p7')
     parser.add_argument('--p47', action='store_true',
                        help='Static features only: p4→ch0, p5→ch1, p6→ch2, p7→ch3')