Unable to read from large ascii data file

ROOT
1

Hello,
I’m trying to get a tree from an ASCII data file, which is of about 3 Gb.
But when I try

[code]int getdatatree(char *filename) {
FILE *input = fopen(filename, “r”);

if (input == NULL) return 1;

TFile *rootfile = new TFile("data.root", "RECREATE");

TTree *t = new TTree("data", "data read from file");

Int_t n;
Int_t m;
Double_t x;
Double_t y;
Double_t z;
Double_t w;

t->Branch("a", &n);
t->Branch("b", &m);
t->Branch("c", &x);
t->Branch("d", &y);
t->Branch("e", &z);
t->Branch("f", &w);


while (feof(input) == 0) {
	if (fscanf(input, "%d %d", &n, &m) != 2) break;
	
	if (fscanf(input, "%lf %lf %lf %lf", &x, &y, &z, &w) != 4) break;
	t->Fill();	
}
	
rootfile->Write();

fclose(input);
rootfile->Close();

return 0;

}
[/code]

I get 1 as return value, and obviously the tree is not filled.

Is there any solution?

Thanks,
Rene

2

And if it is not the case (e.g. if there is no solution to this which seems to be a file offset bits related issue), is there any way to automatically read multiple files with a same pattern?
I mean, in C I would do

[code]int main(int argc, char **argv) {
int i;

if (argc < 2) return 1;

for (i = 1; i < argc; i++) {
	/* read data from the file "argv[i]"
	   and then update the tree */
}

printf("%d files read\n", argc-1);

return 0;

}[/code]
calling this using

3

Hi,

[quote]I get 1 as return value, and obviously the tree is not filled. [/quote] so the line FILE *input = fopen(filename, "r"); fails. You may need to use fopen64 and/or use a 64b build.

Cheers,
Philippe.

4

I tried, but in the ROOT prompt I got

Error: Function fopen64(filename,"r") is not defined in current scope  prova.c:20:

while if I compile the macro, after some seconds of computation I get a segmentation violation error.

This is the header I added:

[code]#include
#include <TObject.h>
#include <TString.h>
#include <TCut.h>
#include <TTimeStamp.h>
#include <TTree.h>
#include <TFile.h>
#include <TROOT.h>
#include <TBranch.h>
#include <TNamed.h>
#include <TChain.h>
#include <TMath.h>
#include <TGraphErrors.h>
#include <TMultiGraph.h>
#include <TLegend.h>
#include <TAxis.h>
#include <stdio.h>

extern FILE* fopen64(const char *filename, const char *type);
[/code]

(note the extern definition, otherwise neither ROOT nor gcc seem to recognize fopen64).

Uhm, how can I use a 64b build on my 32 bit SLC5 machine?

Thanks in advance.

5

Hi,

fopen64 is not available via CINT (and anyway you really will need to compile in order to process the 3Gb in a reasonable time).

You can’t :slight_smile:

[quote]while if I compile the macro, after some seconds of computation I get a segmentation violation error.
[/quote]What is the stack trace?

Cheers,
Philippe.