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How do I read/write files in parallel using UDF?

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Old   December 6, 2022, 05:57
Default How do I read/write files in parallel using UDF?
  #1
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Hey all, I'm trying to create a udf that reads a file containing x,y,z coordinates and then returning the value of the cell nearest to it. I managed to create the code, but I have trouble parallelizing it. At first, I had trouble because ansys repeats my udf 4 times (which is equal to the number of solver processes I input), so I decided to just use my udf on compute node zero by using if(I_AM_NODE_ZERO_P). However, I began to realize that this will fail because the other compute nodes will not be processed, and thus the I will not get the cell values at those compute nodes. My question now is, how do I parallelize reading/writing csv files using UDF? I consulted the ansys documentation on parallelizing udf, but I do not know how to start. Here is my code:

Code:
#include <udf.h>
#include <cxndsearch.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static ND_Search *domain_table = NULL;

DEFINE_ON_DEMAND(find_cells)
{
    #if !RP_HOST
    if(I_AM_NODE_ZERO_P){
    cell_t c;
    Thread *t;
    CX_Cell_Id *cx_cell;
    real cCentroid;
    real cVolume;


    real P[3];
    real P_Cell[3];

    FILE *fp;
    char line[1024];
    int rayID, side, prevID, nextID, surfID;
    double x,y,z;

    fp = fopen("rays_csv_new.csv","r");

    if(fp == NULL){
        printf("Trouble reading file\nAborting..");
        fclose(fp);
        abort();
    }

    domain_table = CX_Start_ND_Point_Search(domain_table,TRUE,-1);
    Message("Starting Cell Search...");

    while(fgets(line,1024,fp)){
        sscanf(line,"%d,%lg,%lg,%lg,%d,%d,%d,%d",&rayID,&x,&y,&z,&side,&prevID,&nextID,&surfID);
        P[0] = x;
        P[1] = y;
        P[2] = z;

        cx_cell = CX_Find_Cell_With_Point(domain_table,P,0.0);

        if(cx_cell){
            c = RP_CELL(cx_cell);
            t = RP_THREAD(cx_cell);
            cCentroid = C_CENTROID(P_Cell,c,t);
            cVolume = C_VOLUME(c,t);

            Message("%g \t %g \t %g \t %g\n",P[0],P[1],P[2],cVolume);

        }else{
            Message("Could not find cell at [%g,%g,%g]\n",P[0],P[1],P[2]);
        }
    }
    domain_table = CX_End_ND_Point_Search(domain_table);
    fclose(fp);
    }
    #endif
}
I tested my code the following dataset:

Code:
x y z
0.227898,1.0,-0.448053
4,-0.106937,1.0,0.379007
7,-0.350153,1.0,0.031367
9,0.293532,1.0,0.357582
11,-0.403077,1.0,-0.409584
13,0.476352,1.0,-0.0787738
15,-0.400827,1.0,-0.0563139
18,0.189004,1.0,0.217153
Since I was only processing compute node 0, the cells that are within compute node 0 will be found, but those that are outside it won't. As a result, the output looks like this:

Code:
Could not find cell at [0.227898,1,-0.448053]
Could not find cell at [-0.106937,1,0.379007]
Could not find cell at [-0.350153,1,0.0313674]
0.293532 	 1 	 0.357582 	 1.82506e-08
Could not find cell at [-0.403077,1,-0.409584]
Could not find cell at [0.476352,1,-0.0787738]
Could not find cell at [-0.400827,1,-0.0563139]
0.189004 	 1 	 0.217153 	 1.95857e-08
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Old   December 7, 2022, 02:26
Default
  #2
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Alexander
Join Date: Apr 2013
Posts: 2,363
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AlexanderZ will become famous soon enoughAlexanderZ will become famous soon enough
try this code,
modify FL variable which represents the number of lines into your table file
Code:
#include <udf.h>
#include <cxndsearch.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define FL	100 /*file length*/

static ND_Search *domain_table = NULL;
int rayID[FL], side[FL], prevID[FL], nextID[FL], surfID[FL];
real x[FL],y[FL],z[FL];
	
void my_read_from_table(char *file)
{
	FILE *fp;
	char line[1024];
	int i=0;
	fp = fopen(file,"r");

    if(fp == NULL){
        printf("Trouble reading file\nAborting..");
        fclose(fp);
        abort();
    }	
	while(fgets(line,1024,fp)){
        sscanf(line,"%d,%lf,%lf,%lf,%d,%d,%d,%d",&rayID[i],&x[i],&y[i],&z[i],&side[i],&prevID[i],&nextID[i],&surfID[i]);
		i++;
	}
	fclose(fp);
	Message("DEBUG: last line from table:\n %d,%f,%f,%f,%d,%d,%d,%d \n",rayID[FL],x[FL],y[FL],z[FL],side[FL],prevID[FL],nextID[FL],surfID[FL]);
}

DEFINE_ON_DEMAND(find_cells)
{
    cell_t c;
    Thread *t;
    CX_Cell_Id *cx_cell;
    real cCentroid;
    real cVolume;
    real P[3];
    real P_Cell[3];
	int i;

	#if !RP_NODE
		my_read_from_table("rays_csv_new.csv");
	#endif
	host_to_node_int(rayID,FL);
	host_to_node_int(side,FL);
	host_to_node_int(prevID,FL);
	host_to_node_int(nextID,FL);
	host_to_node_int(surfID,FL);
	
	host_to_node_int(x,FL);
	host_to_node_int(y,FL);
	host_to_node_int(z,FL);
	#if !RP_HOST
    domain_table = CX_Start_ND_Point_Search(domain_table,TRUE,-1);
    Message0("Starting Cell Search...");

	for (i=0;i<FL;i++)
	{
		P[0] = x[i];
        P[1] = y[i];
        P[2] = z[i];	
		cx_cell = CX_Find_Cell_With_Point(domain_table,P,0.0);

        if(cx_cell){
            c = RP_CELL(cx_cell);
            t = RP_THREAD(cx_cell);
            cCentroid = C_CENTROID(P_Cell,c,t);
            cVolume = C_VOLUME(c,t);

            Message0("%f \t %f \t %f \t %f\n",P[0],P[1],P[2],cVolume);

        }else{
            Message0("Could not find cell at [%f,%f,%f]\n",P[0],P[1],P[2]);
        }
    }
    domain_table = CX_End_ND_Point_Search(domain_table);
    #endif
}
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Old   December 7, 2022, 02:43
Default
  #3
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Quote:
Originally Posted by AlexanderZ View Post
try this code,
modify FL variable which represents the number of lines into your table file
Code:
#include <udf.h>
#include <cxndsearch.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define FL	100 /*file length*/

static ND_Search *domain_table = NULL;
int rayID[FL], side[FL], prevID[FL], nextID[FL], surfID[FL];
real x[FL],y[FL],z[FL];
	
void my_read_from_table(char *file)
{
	FILE *fp;
	char line[1024];
	int i=0;
	fp = fopen(file,"r");

    if(fp == NULL){
        printf("Trouble reading file\nAborting..");
        fclose(fp);
        abort();
    }	
	while(fgets(line,1024,fp)){
        sscanf(line,"%d,%lf,%lf,%lf,%d,%d,%d,%d",&rayID[i],&x[i],&y[i],&z[i],&side[i],&prevID[i],&nextID[i],&surfID[i]);
		i++;
	}
	fclose(fp);
	Message("DEBUG: last line from table:\n %d,%f,%f,%f,%d,%d,%d,%d \n",rayID[FL],x[FL],y[FL],z[FL],side[FL],prevID[FL],nextID[FL],surfID[FL]);
}

DEFINE_ON_DEMAND(find_cells)
{
    cell_t c;
    Thread *t;
    CX_Cell_Id *cx_cell;
    real cCentroid;
    real cVolume;
    real P[3];
    real P_Cell[3];
	int i;

	#if !RP_NODE
		my_read_from_table("rays_csv_new.csv");
	#endif
	host_to_node_int(rayID,FL);
	host_to_node_int(side,FL);
	host_to_node_int(prevID,FL);
	host_to_node_int(nextID,FL);
	host_to_node_int(surfID,FL);
	
	host_to_node_int(x,FL);
	host_to_node_int(y,FL);
	host_to_node_int(z,FL);
	#if !RP_HOST
    domain_table = CX_Start_ND_Point_Search(domain_table,TRUE,-1);
    Message0("Starting Cell Search...");

	for (i=0;i<FL;i++)
	{
		P[0] = x[i];
        P[1] = y[i];
        P[2] = z[i];	
		cx_cell = CX_Find_Cell_With_Point(domain_table,P,0.0);

        if(cx_cell){
            c = RP_CELL(cx_cell);
            t = RP_THREAD(cx_cell);
            cCentroid = C_CENTROID(P_Cell,c,t);
            cVolume = C_VOLUME(c,t);

            Message0("%f \t %f \t %f \t %f\n",P[0],P[1],P[2],cVolume);

        }else{
            Message0("Could not find cell at [%f,%f,%f]\n",P[0],P[1],P[2]);
        }
    }
    domain_table = CX_End_ND_Point_Search(domain_table);
    #endif
}
Hello, thanks for replying. The code seems to be buggy. most of the output I get is:
Could not find cell at [0.000000,0.000000,0.000000]
Could not find cell at [0.000000,0.000000,0.000000]
Could not find cell at [0.000000,0.000000,0.000000]

But I don't think this thread matters anymore since I've decided to just use a serial solver to do the udf. I was hoping you could help me with my other problem located here
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