+extern volatile int cp_line[];
+extern volatile char *cp_file[];
+extern volatile int cp_index;
+
+#define cp { cp_line[cp_index] = __LINE__; cp_file[cp_index] = __FILE__; cp_index++; cp_index %= 8; }
+#define ecp { fprintf(stderr, "Explicit checkpoint in %s line %d\n", __FILE__, __LINE__); }