Segmentation fault when using combiner

Question

Hi,

I'm getting a segmentation fault when using a combiner in a contraction.

The specific example is:

combine =
/--------------IQTensor--------------
r=3 div=QN() log(scale)=0
IQIndex(cmb,8,Link,854)
(c0,1,Link,390) (Sz=-1,Nf=1)
(c1,2,Link,985) (Sz=0,Nf=2)
(c2,1,Link,906) (Sz=1,Nf=3)
(c3,1,Link,69) (Sz=-2,Nf=2)
(c4,2,Link,545) (Sz=-1,Nf=3)
(c5,1,Link,386) (Sz=0,Nf=4)

IQIndex(d,2,Link,168)
(d2,1,Link,997) (Sz=-1,Nf=1)
(d3,1,Link,486) (Sz=0,Nf=2)

IQIndex(site=2,4,Site,268)
(Emp 2,1,Site,200) (Sz=0,Nf=0)
(Up 2,1,Site,598) (Sz=1,Nf=1)
(Dn 2,1,Site,552) (Sz=-1,Nf=1)
(UpDn 2,1,Site,867) (Sz=0,Nf=2)

|-- Data -------
QCombiner
------------------------------------

and the other tensor is:

drho =
/--------------IQTensor--------------
r=7 div=(Sz=-1,Nf=21) log(scale)=5.58209
IQIndex(d,2,Link,168)
(d2,1,Link,997) (Sz=-1,Nf=1)
(d3,1,Link,486) (Sz=0,Nf=2)

IQIndex(L3,1,Link,377)
(l3,1,Link,471) (Sz=0,Nf=4)

IQIndex(site=3,4,Site,172)
(Emp 3,1,Site,898) (Sz=0,Nf=0)
(Up 3,1,Site,547) (Sz=1,Nf=1)
(Dn 3,1,Site,602) (Sz=-1,Nf=1)
(UpDn 3,1,Site,151) (Sz=0,Nf=2)

IQIndex(d,2,Link,168)
(d2,1,Link,997) (Sz=-1,Nf=1)
(d3,1,Link,486) (Sz=0,Nf=2)

IQIndex(L1,1,Link,47)
(l1,1,Link,932) (Sz=0,Nf=8)

IQIndex(MPOIndex,38,Link,584)
(1st i=1,3,Link,248) (Sz=1,Nf=-1)
(cst i=1,2,Link,101) (Sz=-1,Nf=-1)
(cdagup i=1,2,Link,773) (Sz=-1,Nf=1)
(cdagdn i=1,2,Link,670) (Sz=1,Nf=1)
(3rd i=1,8,Link,749) (Sz=0,Nf=0)
(RiNus1,7,Link,17) (Sz=2,Nf=0)
(PiNus1,7,Link,534) (Sz=2,Nf=-2)
(PiNds_1,7,Link,330) (Sz=0,Nf=-2)

IQIndex(site=2,4,Site,268)
(Emp 2,1,Site,200) (Sz=0,Nf=0)
(Up 2,1,Site,598) (Sz=1,Nf=1)
(Dn 2,1,Site,552) (Sz=-1,Nf=1)
(UpDn 2,1,Site,867) (Sz=0,Nf=2)

|-- Data -------
QDense Real {7 blocks; data size 45}
(d3,1,Link,486) (l3,1,Link,471) (UpDn 3,1,Site,151) (d3,1,Link,486) (l1,1,Link,932) (PiNus1,7,Link,534) (Up 2,1,Site,598)
(2,1,4,2,1,31,2) -1.8727
(d3,1,Link,486) (l3,1,Link,471) (UpDn 3,1,Site,151) (d3,1,Link,486) (l1,1,Link,932) (PiNds1,7,Link,330) (Dn 2,1,Site,552)
(2,1,4,2,1,38,3) 2.21107
(d3,1,Link,486) (l3,1,Link,471) (UpDn 3,1,Site,151) (d3,1,Link,486) (l1,1,Link,932) (1st i=1,3,Link,248) (UpDn 2,1,Site,867)
(2,1,4,2,1,1,4) 265.153
(2,1,4,2,1,2,4) -15.364
(d3,1,Link,486) (l3,1,Link,471) (UpDn 3,1,Site,151) (d2,1,Link,997) (l1,1,Link,932) (PiNds_1,7,Link,330) (UpDn 2,1,Site,867)
(2,1,4,1,1,38,4) -2.51961

------------------------------------

if I do drho = combine * drho, I get

Signal: Segmentation fault (11)
Signal code: Address not mapped (1)
Failing at address: 0x8

I hope anyone can help me.

Btw: This happens in the "deltaRho" method of the class "LocalOp" when using a noise term in "fitApplyMPO".

Best,
Lars

Comments

I was able to reproduce this error with the following code:

    auto L = IQIndex("L",Index("L-",2),QN(-1),
                         Index("L0",4),QN( 0),
                         Index("L+",2),QN(+1));
    auto S = IQIndex("S",Index("S-",1),QN(-1),
                         Index("S+",1),QN(+1));
    auto R = IQIndex("R",Index("S-",1),QN(-1),
                         Index("S+",1),QN(+1));

    //Create a zero IQTensor
    auto A = IQTensor(L,S,R);

    auto B = randomTensor(QN(0),dag(L),S, R);

    IQTensor C;
    C = combiner(S, R);
    auto newT = C*B;
    std::stringstream data;
    write(data, C);
    std::cout << data << std::endl;
    IQTensor c2;
    read(data, c2);

    auto newT2 = c2*B;

Hope this helps.
Lars

Answer 1

Fixed by a pull request: https://github.com/ITensor/ITensor/pull/119

Thanks, Lars, for submitting this patch.