OpenACC必须包含常规信息错误 [英] OpenACC must have routine information error
问题描述
我正在尝试并行化一个简单的mandelbrot c程序，但是却出现了与不包含acc例程信息有关的此错误.另外，我不确定是否应将数据复制到并行部分中以及从并行部分中复制数据. PS:我对并行编程还比较陌生，因此，任何有学习建议的人都将不胜感激.
I am trying to parallelize a simple mandelbrot c program, yet I get this error that has to do with not including acc routine information. Also, I am not sure whether I should be copying data in and out of the parallel section. PS I am relatively new to parallel programming, so any advice with learning it would be appreciated.
(编译时警告)
PGC-S-0155-Procedures called in a compute region must have acc routine information: fwrite (mandelbrot.c: 88)
PGC-S-0155-Accelerator region ignored; see -Minfo messages (mandelbrot.c: 51)
main:
51, Accelerator region ignored
88, Accelerator restriction: call to 'fwrite' with no acc routine information
PGC/x86-64 Linux 16.10-0: compilation completed with severe errors
这是我的代码:
#include <stdio.h>
#include <math.h>
int main()
{
/* screen ( integer) coordinate */
int iX,iY;
const int iXmax = 800;
const int iYmax = 800;
/* world ( double) coordinate = parameter plane*/
double Cx,Cy;
const double CxMin=-2.5;
const double CxMax=1.5;
const double CyMin=-2.0;
const double CyMax=2.0;
/* */
double PixelWidth=(CxMax-CxMin)/iXmax;
double PixelHeight=(CyMax-CyMin)/iYmax;
/* color component ( R or G or B) is coded from 0 to 255 */
/* it is 24 bit color RGB file */
const int MaxColorComponentValue=255;
FILE * fp;
char *filename="new1.ppm";
char *comment="# ";/* comment should start with # */
static unsigned char color[3];
/* Z=Zx+Zy*i ; Z0 = 0 */
double Zx, Zy;
double Zx2, Zy2; /* Zx2=Zx*Zx; Zy2=Zy*Zy */
/* */
int Iteration;
const int IterationMax=200;
/* bail-out value , radius of circle ; */
const double EscapeRadius=2;
double ER2=EscapeRadius*EscapeRadius;
/*create new file,give it a name and open it in binary mode */
fp= fopen(filename,"wb"); /* b - binary mode */
/*write ASCII header to the file*/
fprintf(fp,"P6\n %s\n %d\n %d\n %d\n",comment,iXmax,iYmax,MaxColorComponentValue);
/* compute and write image data bytes to the file*/
#pragma acc parallel loop present(CyMin, iY, PixelHeight, iX, iXmax, CxMin, PixelWidth, Zx, Zy, Zx2, Zy2, Iteration, IterationMax)
for(iY=0;iY<iYmax;iY++)
{
Cy=CyMin + iY*PixelHeight;
if (fabs(Cy)< PixelHeight/2) Cy=0.0; /* Main antenna */
#pragma acc loop
for(iX=0;iX<iXmax;iX++)
{
Cx=CxMin + iX*PixelWidth;
/* initial value of orbit = critical point Z= 0 */
Zx=0.0;
Zy=0.0;
Zx2=Zx*Zx;
Zy2=Zy*Zy;
/* */
#pragma acc loop
for (Iteration=0;Iteration<IterationMax && ((Zx2+Zy2)<ER2);Iteration++)
{
Zy=2*Zx*Zy + Cy;
Zx=Zx2-Zy2 +Cx;
Zx2=Zx*Zx;
Zy2=Zy*Zy;
};
/* compute pixel color (24 bit = 3 bytes) */
if (Iteration==IterationMax)
{ /* interior of Mandelbrot set = black */
color[0]=0;
color[1]=0;
color[2]=0;
}
else
{ /* exterior of Mandelbrot set = white */
color[0]=255; /* Red*/
color[1]=255; /* Green */
color[2]=255;/* Blue */
};
/*write color to the file*/
fwrite(color,1,3,fp);
}
}
fclose(fp);
return 0;
}
推荐答案
由于无法从GPU访问文件，因此需要将结果捕获到数组中，然后将其复制回主机，然后输出结果保存到文件中.
Since you can't access a file from the GPU, you'll want to capture the results to arrays, copy them back to the host, and then output the results to a file.
此外，"present"子句表示您已将数据复制到设备上，如果程序不在其中，则程序将中止.考虑到用法，我认为您打算使用专用"，这表示变量应在执行级别专用.但是，默认情况下，标量在OpenACC中是私有的，因此无需手动私有化这些变量.如果您确实手动对变量进行私有化，请确保将其置于正确的循环级别.例如，如果在外部循环上对"Zx"进行私有化，则它将仅私有于该循环级别.内循环的所有向量都将共享它！同样，在这里，最好只让编译器处理标量的私有化，但要注意在少数情况下必须手动私有化变量的情况下将私有化的地方.
Also, the "present" clause indicates that you've already copied the data over to the device and the program will abort if it's not there. Given the usage, I think you meant to use "private", which indicates that the variable should be private to the execution level. However scalars are private by default in OpenACC, so there's no need to manually privatize these variables. If you do manually privatize a variable, be sure to put it at the correct loop level. For example, if you privatize "Zx" on the outer loop, it will only private to that loop level. It would be shared by all the vectors of the inner loop! Again, here, it's best to just let the compiler handle privatizing the scalars, but just be mindful of where you privatize things in the few cases where you have to manually privatize variables.
这是您的代码的正确版本.
Here's a corrected version of your code.
#include <stdio.h>
#include <math.h>
int main()
{
/* screen ( integer) coordinate */
int iX,iY;
const int iXmax = 800;
const int iYmax = 800;
/* world ( double) coordinate = parameter plane*/
double Cx,Cy;
const double CxMin=-2.5;
const double CxMax=1.5;
const double CyMin=-2.0;
const double CyMax=2.0;
/* */
double PixelWidth=(CxMax-CxMin)/iXmax;
double PixelHeight=(CyMax-CyMin)/iYmax;
/* color component ( R or G or B) is coded from 0 to 255 */
/* it is 24 bit color RGB file */
const int MaxColorComponentValue=255;
FILE * fp;
char *filename="new1.ppm";
char *comment="# ";/* comment should start with # */
static unsigned char color[3];
unsigned char red[iXmax][iYmax];
unsigned char blue[iXmax][iYmax];
unsigned char green[iXmax][iYmax];
/* Z=Zx+Zy*i ; Z0 = 0 */
double Zx, Zy;
double Zx2, Zy2; /* Zx2=Zx*Zx; Zy2=Zy*Zy */
/* */
int Iteration;
const int IterationMax=200;
/* bail-out value , radius of circle ; */
const double EscapeRadius=2;
double ER2=EscapeRadius*EscapeRadius;
/*create new file,give it a name and open it in binary mode */
fp= fopen(filename,"wb"); /* b - binary mode */
/*write ASCII header to the file*/
fprintf(fp,"P6\n %s\n %d\n %d\n %d\n",comment,iXmax,iYmax,MaxColorComponentValue);
/* compute and write image data bytes to the file*/
#pragma acc parallel loop copyout(red,blue,green)
for(iY=0;iY<iYmax;iY++)
{
Cy=CyMin + iY*PixelHeight;
if (fabs(Cy)< PixelHeight/2) Cy=0.0; /* Main antenna */
#pragma acc loop
for(iX=0;iX<iXmax;iX++)
{
Cx=CxMin + iX*PixelWidth;
/* initial value of orbit = critical point Z= 0 */
Zx=0.0;
Zy=0.0;
Zx2=Zx*Zx;
Zy2=Zy*Zy;
/* */
#pragma acc loop
for (Iteration=0;Iteration<IterationMax && ((Zx2+Zy2)<ER2);Iteration++)
{
Zy=2*Zx*Zy + Cy;
Zx=Zx2-Zy2 +Cx;
Zx2=Zx*Zx;
Zy2=Zy*Zy;
};
/* compute pixel color (24 bit = 3 bytes) */
if (Iteration==IterationMax)
{ /* interior of Mandelbrot set = black */
red[iX][iY]=0;
blue[iX][iY]=0;
green[iX][iY]=0;
}
else
{ /* exterior of Mandelbrot set = white */
red[iX][iY]=255;
blue[iX][iY]=255;
green[iX][iY]=255;
}; }
}
/*write color to the file*/
for(iY=0;iY<iYmax;iY++) {
for(iX=0;iX<iXmax;iX++) {
color[0] = red[iX][iY];
color[1] = blue[iX][iY];
color[2] = green[iX][iY];
fwrite(color,1,3,fp);
}
}
fclose(fp);
return 0;
}
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