Can't read a tree branch with leaves of varied length array

ROOT
1

Hello, ROOTers:

I have a root file pi0.FmsEmJet.root (414.1 KB)
and I need to read it. The tree in the root file has branches with multiple leaves, and some of the leaves are array of varied size.

******************************************************************************
*Tree    :FmsEmJet  : Fms Em Jet                                             *
*Entries :     3594 : Total =          949844 bytes  File  Size =     419197 *
*        :          : Tree compression factor =   2.27                       *
******************************************************************************
*Br    0 :hit       : nHits/I:detId[nHits]/I:ch[nHits]/I:e[nHits]/F          *
*Entries :     3594 : Total  Size=     719647 bytes  File Size  =     250772 *
*Baskets :       23 : Basket Size=      32000 bytes  Compression=   2.87     *
*............................................................................*
*Br    1 :clu       : nClus/I:e[nClus]/F:x[nClus]/F:y[nClus]/F               *
*Entries :     3594 : Total  Size=     113834 bytes  File Size  =      76164 *
*Baskets :        4 : Basket Size=      32000 bytes  Compression=   1.48     *
*............................................................................*
*Br    2 :point     : nPoints/I:e[nPoints]/F:x[nPoints]/F:y[nPoints]/F       *
*Entries :     3594 : Total  Size=     115974 bytes  File Size  =      91104 *
*Baskets :        5 : Basket Size=      32000 bytes  Compression=   1.26     *
*............................................................................*

I read the branch by constructing corresponding struct for each branch.
test.C (1.2 KB)

struct hit_t {
    int n;
    int detId[256];
    int ch[256];
    float e[256];
};

struct cluster_t {
    int n;
    float e[16];
    float x[16];
    float y[16];
};

struct point_t {
    int n;
    float e[16];
    float x[16];
    float y[16];
};

void test(const char*fname = "pi0.FmsEmJet.root")
{
    TFile *fin = new TFile(fname, "read");
    TTree *tin = (TTree*) fin->Get("FmsEmJet");
    struct hit_t hit;
    struct cluster_t clu;
    struct point_t point;
    tin->SetBranchAddress("hit", &hit);
    tin->SetBranchAddress("clu", &clu);
    tin->SetBranchAddress("point", &point);

    // const int nEntries = tin->GetEntries();
    const int nEntries = 1;
    for (int ei=0; ei<nEntries; ei++)
    {
	tin->GetEntry(ei);
	cout << "hit\t" << hit.n << "\t";
	for (int hi=0; hi<hit.n; hi++)
	    cout << hit.e[hi] << "\t";
	cout << endl;

	cout << "clu\t" << clu.n << "\t";
	for (int ci=0; ci<clu.n; ci++)
	    cout << clu.e[ci] << "\t" << clu.x[ci] << "\t" << clu.y[ci];
	cout << endl;

	cout << "point\t" << point.n << "\t";
	for (int pi=0; pi<point.n; pi++)
	    cout << point.e[pi] << "\t" << point.x[pi] << "\t" << point.y[pi];
	cout << endl;
    }

    fin->Close();
}

Unfortunately, the readout value is nonsense (except the size value). I don’t know why (I am sure that the array in each struct is large enough). Can anyone help? Thanks in advance.

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ROOT Version: 6.28.06
Platform: Ubuntu 22.04
Compiler: Not Provided

2

Try with

struct hit_t {
    int n = 256;
    int detId[256];
    int ch[256];
    float e[256];
};

struct cluster_t {
    int n = 16;
    float e[16];
    float x[16];
    float y[16];
};

struct point_t {
    int n = 16;
    float e[16];
    float x[16];
    float y[16];
}
3

No, I got the same result.

4

Any new thoughts?

5

with your initial code I get:

hit	2	4.5765e-41	4.92502e-25	
clu	1	7.5	1.4013e-45	4.59051e-41
point	1	43.9833	3.44383e-41	4.59051e-41

with @pcanal suggestion I get:

hit	2	0	1.21605e-37	
clu	1	7.5	4.59051e-41	4.59051e-41
point	1	43.9833	1.4013e-45	4.59051e-41

so it is not the same result.

6

@couet

root pi0.FmsEmJet.root -e 'FmsEmJet->Scan("*", "", "", 1);' -q

7

@Wile_E_Coyote , Yes you are right, the file is tree is quite empty, and sometimes undefined…
I did not check. Thanks.

% root pi0.FmsEmJet.root -e 'FmsEmJet->Scan("*", "", "", 1);' -q
***********************************************************************************************************************************************************************
*    Row   * Instance * hit.hit.n * hit.hit.d * hit.hit.c * hit.hit.e * clu.clu.n * clu.clu.e * clu.clu.x * clu.clu.y * point.poi * point.poi * point.poi * point.poi *
***********************************************************************************************************************************************************************
*        0 *        0 *         2 *         8 *         8 * 1.7510000 *         1 * 1.9390000 *       0.5 *       7.5 *         1 * 1.9390000 * 2.8681945 * 43.983348 *
*        0 *        1 *         2 *         8 *         8 * 0.1879999 *         1 *           *           *           *         1 *           *           *           *
***********************************************************************************************************************************************************************
8

I mean both readouts are not what I expected. You can easily check out the energy or position by ‘FmsEmJet->Show(0)’.

9

The tree is not undefined. It shows so because it has leaves which are arrays of varied length.

10

I see:

======> EVENT:0
 nHits           = 2
 detId           = 8, 
                  8
 ch              = 8, 
                  8
 e               = 1.751, 
                  0.188
 nClus           = 1
 e               = 1.939
 x               = 0.5
 y               = 7.5
 nPoints         = 1
 e               = 1.939
 x               = 2.86819
 y               = 43.9833
root [2] FmsEmJet->Scan("*", "", "", 1)
***********************************************************************************************************************************************************************
*    Row   * Instance * hit.hit.n * hit.hit.d * hit.hit.c * hit.hit.e * clu.clu.n * clu.clu.e * clu.clu.x * clu.clu.y * point.poi * point.poi * point.poi * point.poi *
***********************************************************************************************************************************************************************
*        0 *        0 *         2 *         8 *         8 * 1.7510000 *         1 * 1.9390000 *       0.5 *       7.5 *         1 * 1.9390000 * 2.8681945 * 43.983348 *
*        0 *        1 *         2 *         8 *         8 * 0.1879999 *         1 *           *           *           *         1 *           *           *           *
***********************************************************************************************************************************************************************

How are the result of Show or Scan not what you expect?

11

The cluster energy is 1.939, x and y being 0.5 and 7.5. Obviously not what I got when using the “TTree::SetBranchAddress” method.

12

Indeed. TTree::SetBranchAddress is having difficulty with this tree structure. You can solve the problem by adding a series of call like the following for each and every arrays before the call to TTree::SetBranchAddress

tin->GetLeaf("clu.e")->SetOffset( sizeof(int) );
tin->GetLeaf("clu.x")->SetOffset( sizeof(int) + sizeof(float)*16 ); 
tin->GetLeaf("clu.y")->SetOffset( sizeof(int) + sizeof(float)*16*2 );
// alternatively:  
// tin->GetLeaf("clu.x")->SetOffset(  ((char*)(&(clu.x[0])))-((char*)(&clu)) );
// tin->GetLeaf("clu.y")->SetOffset(  ((char*)(&(clu.y[0])))-((char*)(&clu)) );

[correction to use the TTree variable name used in the original example]

13

@pcanal Same problem here: “*Break* segmentation violation and failed to access leaf in array from tree contains CORSIKA data”
The solution was to use “TBranch::GetLeaf” + “TLeaf::SetAddress”.

14

Yes, this will also work.

15

It works, thank you very much.

I am also curious why the SetBranchAddress method with a struct doesn’t work.

16

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