我正在尝试编写一个使用 OpenCL 执行蒙特卡罗模拟的程序。我遇到了一个涉及指数的问题。当变量steps的值变大(大约20000)时,指数计算意外失败,程序以“Abort Trap: 6”退出。鉴于步骤不应影响内存分配,这似乎是一个奇怪的错误。我尝试将 normal、alpha 和 beta 设置为 0,但这并不能解决问题,但是注释掉指数并将其替换为常数 1 似乎解决了这个问题。我已在 AWS GPU 实例上运行我的代码,并且没有遇到任何问题。有人知道为什么这可能是集成显卡上的问题吗?
解决方案
在较小的范围内多次执行内核,以将内核执行时间控制在 5 秒以内
代码片段
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
static uint MWC64X(uint2 *state) {
enum { A = 4294883355U };
uint x = (*state).x, c = (*state).y;
uint res = x ^ c;
uint hi = mul_hi(x, A);
x = x * A + c;
c = hi + (x < c);
*state = (uint2)(x, c);
return res;
}
__kernel void discreteMonteCarloKernel(...) {
float cumulativeWalk = stockPrice;
float currentValue = stockPrice;
...
uint n = get_global_id(0);
uint2 seed2 = (uint2)(n, seed);
uint random1 = MWC64X(&seed2);
uint2 seed3 = (uint2)(random1, seed);
uint random2 = MWC64X(&seed3);
float alpha = (interestRate - 0.5 * sigma * sigma) * dt;
float beta = sigma * sqrt(dt);
float u1;
float u2;
float a;
float b;
float normal;
for (int j = 0; j < steps; j++) {
random1 = MWC64X(&seed2);
if (random1 == 0) {
random1 = MWC64X(&seed2);
}
random2 = MWC64X(&seed3);
u1 = (float)random1 / (float)0xffffffff;
u2 = (float)random2 / (float)0xffffffff;
a = sqrt(-2 * log(u1));
b = 2 * M_PI * u2;
normal = a * sin(b);
exponent = exp(alpha + beta * normal);
currentValue = currentValue * exponent;
cumulativeWalk += currentValue;
...
}
问题报告
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Application Specific Information:
abort() called
Application Specific Signatures:
Graphics hardware encountered an error and was reset: 0x00000813
Thread 0 Crashed:: Dispatch queue: opencl_runtime
0 libsystem_kernel.dylib 0x00007fffb14bad42 __pthread_kill + 10
1 libsystem_pthread.dylib 0x00007fffb15a85bf pthread_kill + 90
2 libsystem_c.dylib 0x00007fffb1420420 abort + 129
3 libGPUSupportMercury.dylib 0x00007fffa98e6fbf gpusGenerateCrashLog + 158
4 com.apple.driver.AppleIntelHD5000GraphicsGLDriver 0x000000010915f13b gpusKillClientExt + 9
5 libGPUSupportMercury.dylib 0x00007fffa98e7983 gpusQueueSubmitDataBuffers + 168
6 com.apple.driver.AppleIntelHD5000GraphicsGLDriver 0x00000001091aa031 IntelCLCommandBuffer::getNew(GLDQueueRec*) + 31
7 com.apple.driver.AppleIntelHD5000GraphicsGLDriver 0x00000001091a9f99 intelSubmitCLCommands(GLDQueueRec*, unsigned int) + 65
8 com.apple.driver.AppleIntelHD5000GraphicsGLDriver 0x00000001091b00a1 CHAL_INTEL::ChalContext::ChalFlush() + 83
9 com.apple.driver.AppleIntelHD5000GraphicsGLDriver 0x00000001091aa2c3 gldFinishQueue + 43
10 com.apple.opencl 0x00007fff9ffeeb37 0x7fff9ffed000 + 6967
11 com.apple.opencl 0x00007fff9ffef000 0x7fff9ffed000 + 8192
12 com.apple.opencl 0x00007fffa000ccca 0x7fff9ffed000 + 130250
13 com.apple.opencl 0x00007fffa001029d 0x7fff9ffed000 + 144029
14 libdispatch.dylib 0x00007fffb13568fc _dispatch_client_callout + 8
15 libdispatch.dylib 0x00007fffb1357536 _dispatch_barrier_sync_f_invoke + 83
16 com.apple.opencl 0x00007fffa001011d 0x7fff9ffed000 + 143645
17 com.apple.opencl 0x00007fffa000bda6 0x7fff9ffed000 + 126374
18 com.apple.opencl 0x00007fffa00011df clEnqueueReadBuffer + 813
19 simplisticComparison 0x0000000107b953cf BinomialMultiplication::execute(int) + 1791
20 simplisticComparison 0x0000000107b9ec7f main + 767
21 libdyld.dylib 0x00007fffb138c235 start + 1
Thread 1:
0 libsystem_pthread.dylib 0x00007fffb15a50e4 start_wqthread + 0
1 ??? 0x000070000eed6b30 0 + 123145552751408
Thread 2:
0 libsystem_pthread.dylib 0x00007fffb15a50e4 start_wqthread + 0
Thread 3:
0 libsystem_pthread.dylib 0x00007fffb15a50e4 start_wqthread + 0
1 ??? 0x007865646e496d65 0 + 33888479226719589
Thread 0 crashed with X86 Thread State (64-bit):
rax: 0x0000000000000000 rbx: 0x0000000000000006 rcx: 0x00007fff58074078 rdx: 0x0000000000000000
rdi: 0x0000000000000307 rsi: 0x0000000000000006 rbp: 0x00007fff580740a0 rsp: 0x00007fff58074078
r8: 0x0000000000000000 r9: 0x00007fffb140ba50 r10: 0x0000000008000000 r11: 0x0000000000000206
r12: 0x00007f92de80a7e0 r13: 0x00007f92e0008c00 r14: 0x00007fffba29e3c0 r15: 0x00007f92de801a00
rip: 0x00007fffb14bad42 rfl: 0x0000000000000206 cr2: 0x00007fffba280128
Logical CPU: 0
Error Code: 0x02000148
Trap Number: 133
最佳答案
我有一个猜测。驱动程序可能会以两种方式崩溃:
- 我们引用了错误的缓冲区地址。这可能不是你的情况。
- 我们超时(超过 TDR)。内核需要几秒钟的时间才能完成。
我的钱在#2。如果较大的值(步数)使 GPU 运行时间过长,系统就会杀死一些东西。
我不熟悉 Apple 英特尔驱动程序的内部结构,但通常有一种方法可以在极端情况下禁用 TDR。例如。请参阅Windows Documenation了解 TDR 的要点。 (Linux 驱动程序也有办法禁用此功能。)
通常我们希望避免运行需要超长时间的事情,并且以某种方式分解工作负载可能是一个好主意,这样您自然就不会按下这个终止开关。例如。也许将“步骤”分成更小的 block (传入并保存您无法重新计算的部分的状态)。
关于OpenCL Intel Iris 集成显卡退出并出现 Abort Trap 6 : Timeout Issue,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43977822/