avoid zero feature norm

BayesWitnesses · Mar 15, 2020 · be4fde2 · be4fde2
1 parent c332833
commit be4fde2
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Showing 3 changed files with 28 additions and 7 deletions.
diff --git a/m2cgen/assemblers/svm.py b/m2cgen/assemblers/svm.py
@@ -196,7 +196,12 @@ def _cosine_kernel(self, support_vector):
             utils.apply_op_to_expressions(
                 ast.BinNumOpType.ADD,
                 *[utils.mul(ast.FeatureRef(i), ast.FeatureRef(i))
-                  for i in range(len(support_vector))]))
+                  for i in range(len(support_vector))]),
+            to_reuse=True)
+        safe_feature_norm = ast.IfExpr(
+            utils.eq(feature_norm, ast.NumVal(0.0)),
+            ast.NumVal(1.0),
+            feature_norm)
         kernel = self._linear_kernel(support_vector / support_vector_norm)
-        kernel = utils.div(kernel, feature_norm)
+        kernel = utils.div(kernel, safe_feature_norm)
         return kernel
diff --git a/m2cgen/assemblers/utils.py b/m2cgen/assemblers/utils.py
@@ -23,6 +23,10 @@ def lte(l, r):
     return ast.CompExpr(l, r, ast.CompOpType.LTE)
 
 
+def eq(l, r):
+    return ast.CompExpr(l, r, ast.CompOpType.EQ)
+
+
 BIN_EXPR_CLASSES = {
     (False, False): ast.BinNumExpr,
     (True, True): ast.BinVectorExpr,

diff --git a/tests/assemblers/test_svm.py b/tests/assemblers/test_svm.py
@@ -117,11 +117,23 @@ def kernel_ast(sup_vec_value):
                     ast.NumVal(sup_vec_value),
                     ast.FeatureRef(0),
                     ast.BinNumOpType.MUL),
-                ast.SqrtExpr(
-                    ast.BinNumExpr(
-                        ast.FeatureRef(0),
-                        ast.FeatureRef(0),
-                        ast.BinNumOpType.MUL)),
+                ast.IfExpr(
+                    ast.CompExpr(
+                        ast.SqrtExpr(
+                            ast.BinNumExpr(
+                                ast.FeatureRef(0),
+                                ast.FeatureRef(0),
+                                ast.BinNumOpType.MUL),
+                        to_reuse=True),
+                        ast.NumVal(0.0),
+                        ast.BinNumOpType.EQ),
+                    ast.NumVal(1.0),
+                    ast.SqrtExpr(
+                        ast.BinNumExpr(
+                            ast.FeatureRef(0),
+                            ast.FeatureRef(0),
+                            ast.BinNumOpType.MUL),
+                        to_reuse=True)),
                 ast.BinNumOpType.DIV))
 
     expected = _create_expected_single_output_ast(