[ring] : Gaussian & Ternary sampler have deterministic tests for coef…

…ficient bounds and will only print a warning if the distribution is not as expected.

ring/ring_test.go

@@ -333,11 +333,18 @@ func testGaussianSampler(testContext *testParams, t *testing.T) {
 			coeffs[i] = float64(c.Int64())
 		}
 
+		// Checks that the coefficient are within the bounds
+		for _, c := range coeffs {
+			require.True(t, math.Abs(c) <= float64(DefaultBound))
+		}
+
 		// Computes the standard deviation
-		std := StandardDeviation(coeffs, 1.0)
+		sigma := StandardDeviation(coeffs, 1.0)
 
-		// Checks it stays within small bounds
-		require.True(t, (std < DefaultSigma+0.1) && (std > DefaultSigma-0.1))
+		// Print a warning the distance is too large
+		if math.Abs(sigma-DefaultSigma) > DefaultSigma*0.05 {
+			t.Log("warning : |(sigma - DefaultSigma)| > DefaultSigma * 0.05")
+		}
 	})
 }
 
@@ -376,14 +383,21 @@ func testTernarySampler(testContext *testParams, t *testing.T) {
 				coeffs[i] = float64(c.Int64())
 			}
 
+			// Checks that the coefficient are within the bounds
+			for _, c := range coeffs {
+				require.True(t, math.Abs(c) <= 1)
+			}
+
 			// Computes the standard deviation
-			std := StandardDeviation(coeffs, 1.0)
+			sigma := StandardDeviation(coeffs, 1.0)
 
 			// sqrt(1/N * (N * 1 * (1-p))
 			stdWant := math.Sqrt(1 - p)
 
-			// Checks it stays within small bounds
-			require.True(t, (std < stdWant+0.1) && (std > stdWant-0.1))
+			// Print a warning the distance is too large
+			if math.Abs(sigma-stdWant) > stdWant*0.05 {
+				t.Log("warning : |(sigma - sqrt(1-p))| > sqrt(1-p) * 0.05")
+			}
 
 		})
 	}

ring/utils.go

@@ -1,10 +1,11 @@
 package ring
 
 import (
-	"math"
 	"math/bits"
+	"math"
 )
 
+
 // StandardDeviation computes the scaled standard deviation of the input vector.
 func StandardDeviation(vec []float64, scale float64) (std float64) {
 	// We assume that the error is centered around zero