move platt-transform expcetion to python (#270)

Author: jiong-zhang

pecos/core/base.py

@@ -2049,12 +2049,12 @@ def link_calibrator_methods(self):
         """
         corelib.fillprototype(
             self.clib_float32.c_fit_platt_transform_f32,
-            None,
+            c_uint32,
             [c_uint64, POINTER(c_float), POINTER(c_float), POINTER(c_double)],
         )
         corelib.fillprototype(
             self.clib_float32.c_fit_platt_transform_f64,
-            None,
+            c_uint32,
             [c_uint64, POINTER(c_double), POINTER(c_double), POINTER(c_double)],
         )
 
@@ -2080,14 +2080,14 @@ def fit_platt_transform(self, logits, tgt_prob):
         AB = np.array([0, 0], dtype=np.float64)
 
         if tgt_prob.dtype == np.float32:
-            clib.clib_float32.c_fit_platt_transform_f32(
+            return_code = clib.clib_float32.c_fit_platt_transform_f32(
                 len(logits),
                 logits.ctypes.data_as(POINTER(c_float)),
                 tgt_prob.ctypes.data_as(POINTER(c_float)),
                 AB.ctypes.data_as(POINTER(c_double)),
             )
         elif tgt_prob.dtype == np.float64:
-            clib.clib_float32.c_fit_platt_transform_f64(
+            return_code = clib.clib_float32.c_fit_platt_transform_f64(
                 len(logits),
                 logits.ctypes.data_as(POINTER(c_double)),
                 tgt_prob.ctypes.data_as(POINTER(c_double)),
@@ -2096,7 +2096,20 @@ def fit_platt_transform(self, logits, tgt_prob):
         else:
             raise ValueError(f"Unsupported dtype: {tgt_prob.dtype}")
 
-        return AB[0], AB[1]
+        PLATT_RETURN_CODE = {
+            "SUCCESS": 0,
+            "LINE_SEARCH_FAIL": 1,
+            "MAX_ITER_REACHED": 2,
+        }
+
+        if return_code == PLATT_RETURN_CODE["SUCCESS"]:
+            return AB[0], AB[1]
+        elif return_code == PLATT_RETURN_CODE["LINE_SEARCH_FAIL"]:
+            raise RuntimeError("fit_platt_transform: Line search fails")
+        elif return_code == PLATT_RETURN_CODE["MAX_ITER_REACHED"]:
+            raise RuntimeError("fit_platt_transform: Reaching maximal iterations")
+        else:
+            raise ValueError(f"Unknown return code {return_code}")
 
 
 clib = corelib(os.path.join(os.path.dirname(os.path.abspath(pecos.__file__)), "core"), "libpecos")

pecos/core/libpecos.cpp

@@ -752,13 +752,13 @@ extern "C" {
     // ==== C Interface of Score Calibrator ====
 
     #define C_FIT_PLATT_TRANSFORM(SUFFIX, VAL_TYPE) \
-    void c_fit_platt_transform ## SUFFIX( \
+    uint32_t c_fit_platt_transform ## SUFFIX( \
         size_t num_samples, \
 	const VAL_TYPE* logits, \
 	const VAL_TYPE* tgt_probs, \
 	double* AB \
     ) { \
-        pecos::fit_platt_transform(num_samples, logits, tgt_probs, AB[0], AB[1]); \
+        return pecos::fit_platt_transform(num_samples, logits, tgt_probs, AB[0], AB[1]); \
     }
     C_FIT_PLATT_TRANSFORM(_f32, float32_t)
     C_FIT_PLATT_TRANSFORM(_f64, float64_t)

pecos/core/utils/newton.hpp

@@ -279,7 +279,14 @@ namespace pecos {
     //  https://github.com/cjlin1/libsvm/blob/master/svm.cpp
 
     template <typename value_type>
-    static void fit_platt_transform(size_t num_samples, const value_type *logits, const value_type *tgt_probs, double& A, double& B) {
+    uint32_t fit_platt_transform(size_t num_samples, const value_type *logits, const value_type *tgt_probs, double& A, double& B) {
+	// define the return code
+	enum {
+	    SUCCESS=0,
+	    LINE_SEARCH_FAIL=1,
+	    MAX_ITER_REACHED=2,
+	};
+
         // hyper parameters
         int max_iter = 100; // Maximal number of iterations
         double min_step = 1e-10;    // Minimal step taken in line search
@@ -292,14 +299,6 @@ namespace pecos {
         A = 0.0; B = 1.0;
         double fval = 0.0;
 
-        // check for out of bound in tgt_probs
-	for (size_t i = 0; i < num_samples; i++) {
-	    if (tgt_probs[i] > 1.0 || tgt_probs[i] < 0) {
-                throw std::runtime_error("fit_platt_transform: target probability out of bound\n");
-	    }
-        }
-
-
         for (size_t i = 0; i < num_samples; i++) {
             double fApB = logits[i] * A + B;
             if (fApB >= 0) {
@@ -376,13 +375,16 @@ namespace pecos {
             }
 
             if (stepsize < min_step) {
-                throw std::runtime_error("fit_platt_transform: Line search fails\n");
+                printf("WARNING: fit_platt_transform: Line search fails\n");
+		return LINE_SEARCH_FAIL;
             }
         }
 
         if (iter >= max_iter) {
-            throw std::runtime_error("fit_platt_transform: Reaching maximal iterations\n");
+            printf("WARNING: fit_platt_transform: Reaching maximal iterations\n");
+	    return MAX_ITER_REACHED;
         }
+	return SUCCESS;
     }
 } // namespace pecos
 #endif