chore: import upstream snapshot with attribution

tools/cpp/checkFile.cpp

@@ -0,0 +1,53 @@
+//
+//  checkFile.cpp
+//  MNN
+//
+//  Created by MNN on 2019/01/22.
+//  Copyright © 2018, Alibaba Group Holding Limited
+//
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <cmath>
+#include <fstream>
+#include <sstream>
+
+using namespace std;
+
+int main(int argc, char* argv[]) {
+    if (argc < 3) {
+        printf("Usage: ./checkFile.out XXX.txt YYY.txt tolerance\n");
+        return 0;
+    }
+
+    // read args
+    const char* file1 = argv[1];
+    const char* file2 = argv[2];
+    float tolerance   = 0.001;
+    if (argc > 3) {
+        std::istringstream ss(argv[3]);
+        ss >> tolerance;
+    }
+
+    // open file
+    std::ifstream input1(file1);
+    assert(!input1.fail());
+    std::ifstream input2(file2);
+    assert(!input2.fail());
+
+    // compare
+    float v1, v2;
+    int pos = 0;
+    while (input1 >> v1) {
+        auto& valid = input2 >> v2;
+        if (::fabsf(v1 - v2) > tolerance) {
+            printf("Error for %d, v1=%.6f, v2=%.6f\n", pos, v1, v2);
+        }
+        pos++;
+        if (!valid) {
+            break;
+        }
+    }
+    return 0;
+}