From eb79d5859957351231abf77b3a50290264d4d87f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Guilherme=20Brand=C3=A3o?=
 <37072140+guilherme-brandao@users.noreply.github.com>
Date: Mon, 20 May 2024 16:57:16 +0100
Subject: [PATCH] Fix edge case zero combined loss (#277)

- Fallback stake-weighted combined loss to `epsilon` if it's equal to
zero

Ticket:
https://linear.app/upshot/issue/ORA-1391/no-weights-in-one-reputerlosses-breaks-the-calcnetworklosses
---
 .../inference_synthesis/network_losses.go     | 11 +++++++++--
 .../network_losses_test.go                    | 19 +++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/x/emissions/keeper/inference_synthesis/network_losses.go b/x/emissions/keeper/inference_synthesis/network_losses.go
index 0986a5d64..b6c77eb4d 100644
--- a/x/emissions/keeper/inference_synthesis/network_losses.go
+++ b/x/emissions/keeper/inference_synthesis/network_losses.go
@@ -100,6 +100,10 @@ func CalcNetworkLosses(
 				fmt.Println("Error updating running weighted average for next combined loss: ", err)
 				return emissions.ValueBundle{}, err
 			}
+			// If the combined loss is zero, set it to epsilon to avoid divide by zero
+			if nextCombinedLoss.Loss.IsZero() {
+				nextCombinedLoss.Loss = epsilon
+			}
 			runningWeightedCombinedLoss = nextCombinedLoss
 
 			// Not all reputers may have reported losses on the same set of inferers => important that the code below doesn't assume that!
@@ -245,11 +249,14 @@ func CalcCombinedNetworkLoss(
 			)
 			if err != nil {
 				fmt.Println("Error updating running weighted average for combined loss: ", err)
-				return alloraMath.ZeroDec(), err
+				return Loss{}, err
 			}
 			runningWeightedCombinedLoss = nextCombinedLoss
 		}
 	}
-
+	// If the combined loss is zero, set it to epsilon to avoid divide by zero
+	if runningWeightedCombinedLoss.Loss.IsZero() {
+		runningWeightedCombinedLoss.Loss = epsilon
+	}
 	return runningWeightedCombinedLoss.Loss, nil
 }
diff --git a/x/emissions/keeper/inference_synthesis/network_losses_test.go b/x/emissions/keeper/inference_synthesis/network_losses_test.go
index 80cbdd494..e92bb5ae5 100644
--- a/x/emissions/keeper/inference_synthesis/network_losses_test.go
+++ b/x/emissions/keeper/inference_synthesis/network_losses_test.go
@@ -176,6 +176,25 @@ func (s *InferenceSynthesisTestSuite) TestCalcCombinedNetworkLoss() {
 			expectedLoss: alloraMath.MustNewDecFromString(".000015456633"),
 			expectedErr:  nil,
 		},
+		{
+			name: "One reputer reporting a zero combined loss",
+			stakesByReputer: map[inference_synthesis.Worker]cosmosMath.Uint{
+				"worker1": inference_synthesis.CosmosUintOneE18(), // 1 token
+			},
+			reportedLosses: &emissions.ReputerValueBundles{
+				ReputerValueBundles: []*emissions.ReputerValueBundle{
+					{
+						ValueBundle: &emissions.ValueBundle{
+							Reputer:       "worker1",
+							CombinedValue: alloraMath.MustNewDecFromString("0"),
+						},
+					},
+				},
+			},
+			epsilon:      alloraMath.MustNewDecFromString("1e-4"),
+			expectedLoss: alloraMath.MustNewDecFromString("1e-4"), // Should be equal to epsilon
+			expectedErr:  nil,
+		},
 	}
 
 	for _, tc := range tests {