Use std::mt19937 for RNG instead of glibc extension.

Makefile

@@ -11,7 +11,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-CFLAGS=-std=gnu99 -g -O3 -fomit-frame-pointer -fno-unroll-loops -Wall -Wstrict-prototypes -Wmissing-prototypes -Wshadow -Wmissing-declarations -Wnested-externs -Wpointer-arith -W -Wno-unused-parameter -Werror -pthread -Wno-tautological-compare
+CPPFLAGS=-g -O3 -fomit-frame-pointer -fno-unroll-loops -Wall -Wshadow -Wmissing-declarations -Wpointer-arith -W -Wno-unused-parameter -Werror -pthread -Wno-tautological-compare
+
+CFLAGS=-std=gnu99 -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs
+CXXFLAGS=-std=gnu++11
+
 LDFLAGS=-g -O3 -static -pthread
 LDLIBS=-lrt -lm
 
@@ -20,9 +24,9 @@ ARCH ?= $(shell uname -m)
 ifeq ($(ARCH),aarch64)
  CAP ?= $(shell cat /proc/cpuinfo | grep -E 'atomics|sve' | head -1)
  ifneq (,$(findstring sve,$(CAP)))
-  CFLAGS+=-march=armv8.2-a+sve
+  CPPFLAGS+=-march=armv8.2-a+sve
  else ifneq (,$(findstring atomics,$(CAP)))
-  CFLAGS+=-march=armv8.1-a+lse
+  CPPFLAGS+=-march=armv8.1-a+lse
  endif
 endif
 
@@ -36,9 +40,9 @@ clean:
 .c.s:
 	$(CC) $(CFLAGS) -S -c $<
 
-multichase: multichase.o permutation.o arena.o util.o
+multichase: multichase.o permutation.o random.o arena.o util.o
 
-multiload: multiload.o permutation.o arena.o util.o
+multiload: multiload.o permutation.o random.o arena.o util.o
 
 fairness: LDLIBS += -lm
 
@@ -51,10 +55,11 @@ depend:
 
 # DO NOT DELETE
 
-arena.o: arena.h
-multichase.o: cpu_util.h timer.h expand.h permutation.h arena.h util.h
-multiload.o: cpu_util.h timer.h expand.h permutation.h arena.h util.h
-permutation.o: permutation.h
+arena.o: arena.h random.h
+multichase.o: cpu_util.h timer.h expand.h permutation.h random.h arena.h util.h
+multiload.o: cpu_util.h timer.h expand.h permutation.h random.h arena.h util.h
+permutation.o: permutation.h random.h
+random.o: random.h
 util.o: util.h
 fairness.o: cpu_util.h expand.h timer.h
 pingpong.o: cpu_util.h timer.h

arena.c

@@ -23,7 +23,7 @@
 #include <sys/syscall.h>
 #include <unistd.h>
 
-#include "permutation.h"
+#include "random.h"
 
 extern int verbosity;
 extern int is_weighted_mbind;

multichase.c

@@ -29,6 +29,7 @@
 #include "cpu_util.h"
 #include "expand.h"
 #include "permutation.h"
+#include "random.h"
 #include "timer.h"
 #include "util.h"
 

multiload.c

@@ -29,6 +29,7 @@
 #include "cpu_util.h"
 #include "expand.h"
 #include "permutation.h"
+#include "random.h"
 #include "timer.h"
 #include "util.h"
 

permutation.c

@@ -20,6 +20,8 @@
 #include <stdbool.h>
 #include <string.h>
 
+#include "random.h"
+
 // some asserts are more expensive than we want in general use, but there are a
 // few i want active even in general use.
 #if 1

permutation.h

@@ -73,47 +73,4 @@ void *generate_chase(const struct generate_chase_common_args *args,
 void *generate_chase_long(const struct generate_chase_common_args *args,
                           size_t mixer_idx, size_t total_par);
 
-//============================================================================
-// Modern multicore CPUs have increasingly large caches, so the LCRNG code
-// that was previously used is not sufficiently random anymore.
-// Now using glibc's reentrant random number generator "random_r"
-// still reproducible on the same platform, although not across systems/libs.
-
-// RNG_BUF_SIZE sets the size of rng_buf below, which is used by initstate_r
-// to decide how sophisticated a random number generator it should use: the
-// larger the state array, the better the random numbers will be.
-// 32 bytes was deemed to generate sufficient entropy.
-#define RNG_BUF_SIZE 32
-extern __thread char *rng_buf;
-extern __thread struct random_data *rand_state;
-
-static inline void rng_init(unsigned thread_num) {
-  rng_buf = (char *)calloc(1, RNG_BUF_SIZE);
-  rand_state = (struct random_data *)calloc(1, sizeof(struct random_data));
-  assert(rand_state);
-  if (initstate_r(thread_num, rng_buf, RNG_BUF_SIZE, rand_state) != 0) {
-    perror("initstate_r");
-    exit(1);
-  }
-}
-
-static inline perm_t rng_int(perm_t limit) {
-  int r1, r2, r3, r4;
-  uint64_t r;
-
-  if (random_r(rand_state, &r1) || random_r(rand_state, &r2)
-    || random_r(rand_state, &r3) || random_r(rand_state, &r4)) {
-    perror("random_r");
-    exit(1);
-  }
-  // Assume that RAND_MAX is at least 16-bit long
-  _Static_assert (RAND_MAX >= (1ul << 16), "RAND_MAX is too small");
-  r = (((uint64_t)r1 <<  0) & 0x000000000000FFFFull) |
-      (((uint64_t)r2 << 16) & 0x00000000FFFF0000ull) |
-      (((uint64_t)r3 << 32) & 0x0000FFFF00000000ull) |
-      (((uint64_t)r4 << 48) & 0xFFFF000000000000ull);
-
-  return r % (limit + 1);
-}
-
 #endif

random.cc

@@ -0,0 +1,27 @@
+/* Copyright 2022 Google Inc. All Rights Reserved. 
+ * Licensed under the Apache License, Version 2.0 (the "License"); 
+ * you may not use this file except in compliance with the License. 
+ * You may obtain a copy of the License at 
+ * 
+ *   http://www.apache.org/licenses/LICENSE-2.0 
+ * 
+ * Unless required by applicable law or agreed to in writing, software 
+ * distributed under the License is distributed on an "AS IS" BASIS, 
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
+ * See the License for the specific language governing permissions and 
+ * limitations under the License. 
+ */
+
+#include "random.h"
+
+#include <random>
+
+static thread_local std::mt19937 engine;
+
+void rng_init(unsigned thread_num) {
+  engine.seed(thread_num);
+}
+
+uint32_t rng_int(uint32_t limit) {
+  return engine() % (limit + 1);
+}

random.h

@@ -0,0 +1,31 @@
+/* Copyright 2022 Google Inc. All Rights Reserved.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef RANDOM_H_INCLUDED
+#define RANDOM_H_INCLUDED
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void rng_init(unsigned thread_num);
+uint32_t rng_int(uint32_t limit);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif