segfault while setting non-cubic reciprocal lattice.

[Alex Buts]

The code below segfaults Mantid on SetupUB while inverting some internal matrix.

WS_Name = 'CNCS_7860_event' Load(Filename='CNCS_7860_event.nxs',OutputWorkspace=WS_Name )

AddSampleLog(Workspace=WS_Name,LogName='Ei',LogText='3',LogType='Number') MD_Name='MD1' SetUB(Workspace=WS_Name,a='10.4165',b='3.4165',c='10.4165',alpha=30,beta=45,gamma=80,u='1,0,0',v='0,1,0') ConvertToMDEvents(InputWorkspace=WS_Name,OutputWorkspace=MD_Name,QDimensions='QhQkQl',QinHKL=False,dEAnalysisMode='Direct',MinValues='-2,-2,-3,-1',MaxValues='2,2,3,3',SplitInto="20,20,20,1") ps=plotSlice(MD_Name, xydim=["Q1","Q2"], slicepoint=[0,0] )

[Alex Buts]

Segfault occurs in UnitCell when inverting some matrices while Gstar become #IND

no permutation is calculated and undefined indexes cause segfailt.

May go unnoticed and cause just wrong results if arrays are initated by 0 during allocation.

Have to go today.

[Alex Buts]

refs #4679 unit test which crashes on win

Changeset: 52c7354c798d7b3e15b86c98369718c430d6dcde

[Andrei Savici]

Maybe we should test this, but for any lattice to be physical the following inequalities should be true:

alpha<beta+gamma
beta<alpha+gamma
gamma<alpha+beta

If one of these changes to equality, than the lattice vectors are all in plane

[Andrei Savici]

if the inequalities above do not hold, you would get a negative volume for the unit cell. For the example above, change alpha to 50. If we want to throw an explicit "angles invalid", we can write a ticket, and put the check in void UnitCell::recalculate().

[Andrei Savici]

Euclid proved the above statement. ​http://aleph0.clarku.edu/~djoyce/java/elements/bookXI/propXI20.html

[Ronald Fowler]

The input values given in the test case are invalid, as can be seen from the references. Using valid angle values the algorithm runs OK, even down to the case of alpha==beta==gamma/2 (i.e. coplanar vectors). Mantid should not crash on invalid inputs such as this and the ticket to update UnitCell:recalculate is a high priority. The test that Alex has added, currently commented out, should be enabled and throw "angles invalid". If the angles are such that the vectors are co-planar, or close to this, a warning message would be useful.

The two debug lines that were added to UnitCell.cpp in the above checkin should be removed.

While checking the input data is physical is important, it is hard to cover all cases. Hence UnitCell should also check that inversion has not failed and throw something suitable in that case.

[Alex Buts]

refs #4679 debugging operations

Changeset: fb6ee04b04acefa86234593fc40d6c7647267804

[Stuart Campbell]

This ticket has been transferred to github issue ​5526