When I followed the tutorial for structure optimization, I have got the following error:
The following floating-point exceptions are signalling: IEEE_INVALID_FLAG IEEE_UNDERFLOW_FLAG IEEE_DENORMAL.
During the calculation, the diagonalization was failed, then it stopped.
After googling, I found the issue that gfortran 4.8 and upper version could arise this problem. But for my situation, even though I installed gfortran 4.7 but the problem was not solved.
Instead, I changed the nrigdk="6 6 6" to "7 7 7" (the tutorial code is following). Then the calculation was completed.

So, do you also have same experience ? Can this be a convergence problem ? Does anyone know what this is ?

Thanks in advance.

<input>

<title>Diamond: Internal-structure optimization</title>

<structure speciespath="$EXCITINGROOT/species">

<crystal scale="6.719">
<basevect> 0.5 0.5 0.0 </basevect>
<basevect> 0.5 0.0 0.5 </basevect>
<basevect> 0.0 0.5 0.5 </basevect>
</crystal>

<species speciesfile="C.xml" rmt="1.20">
<atom coord="0.00 0.00 0.00" />
<atom coord="0.30 0.30 0.30" />
</species>

</structure>

<groundstate
ngridk="6 6 6"
swidth="0.0001">
</groundstate>

<relax></relax>

</input>