Fix focal loss

The loss value should reflect the impact of the gamma parameter, as well.

Fix focal loss
The loss value should reflect the impact of the gamma parameter, as well.
9bb1b6f7 · Adrià Arrufat · Davis E. King · 5cb03656 · 9bb1b6f7
Commit 9bb1b6f7 authored Mar 31, 2022 by Adrià Arrufat Committed by Davis E. King Mar 30, 2022
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dlib/dnn/loss.h dlib/dnn/loss.h +2 -2

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--- a/dlib/dnn/loss.h
+++ b/dlib/dnn/loss.h
@@ -850,14 +850,14 @@ namespace dlib
                    {
                        const float temp = log1pexp(-out_data[idx]);
                        const float focus = std::pow(1 - g[idx], gamma);
-                        loss += y * scale * temp;
+                        loss += y * scale * temp * focus;
                        g[idx] = y * scale * focus * (g[idx] * (gamma * temp + 1) - 1);
                    }
                    else
                    {
                        const float temp = -(-out_data[idx] - log1pexp(-out_data[idx]));
                        const float focus = std::pow(g[idx], gamma);
-                        loss += -y * scale * temp;
+                        loss += -y * scale * temp * focus;
                        g[idx] = -y * scale * focus * g[idx] * (gamma * temp + 1);
                    }
                }