System test is hanging due to read/write locking

[Janik Zikovsky]

Here is the smallest code to reproduce the problem:

LoadEventNexus(OutputWorkspace="EQSANS_4061_event", Filename="EQSANS_4061_event.nxs")
EQSANSNormalise(InputWorkspace="EQSANS_4061_event", NormaliseToBeam='0')

The issue is that there is a parent python algorithm (EQSANSNormalise) that calls child algorithms (Scale) but these are not marked as such.

The way read/write locking works for C++ algorithms with children is:

• The parent algorithm locks the input/output workspaces
• The child algorithms do NOT do any locking.

With the EQSANSNormalise, it has its InputWorkspace erroneously set as "Input" (not InOut which is what it really is).

• EQSANSNormalise read-locks the workspace
• Then Scale tries to write-lock, so it hangs.

If EQSANSNormalise has its InputWorkspace set as InOut, it throws an exception when trying to double-write-lock.

So Martyn, what I need to do is to have the algorithms called in a Python algorithm to be set as "child". Do you know how to do that?

[Janik Zikovsky]

Refs #4554 debugging output for locking

Changeset: dc5a5b22ded47a49b80cb6ffd7d990d697b74eb4

[Janik Zikovsky]

Refs #2636, #4752: make python algo's child algorithms set as children

Changeset: 2685a3810c9032b3a82319362f73d6d9c47bbe2c

[Janik Zikovsky]

Refs #2636, #4752: method for children of python algorithms

Changeset: cb95b77c2142d57d65ce2834ac31a481ce5cc9f4

[Janik Zikovsky]

Refs #2636, #4752: enabling use of the method for

python algorithm child algos

Changeset: 377a143c163aabdedf25c8cd16da428751b33220

[Janik Zikovsky]

Looks like system tests / python algorithms with children no longer hang.

[Janik Zikovsky]

I made a mistake and left the locking disabled when I last checked in. Some system tests are indeed failing.

[Janik Zikovsky]

For example:

from MantidFramework import *
mtd.initialise(False)
from mantidsimple import *
from reduction.instruments.sans.hfir_command_interface import *

mtd.settings['default.facility'] = 'HFIR'
HFIRSANS()
    
DirectBeamCenter("BioSANS_empty_cell.xml")
AppendDataFile("BioSANS_test_data.xml")
SetTransmission(0.51944, 0.011078)
SensitivityCorrection("BioSANS_flood_data.xml", dark_current="BioSANS_dark_current.xml")
AzimuthalAverage(binning="0.01,0.001,0.11", error_weighting=True)
Reduce1D()

it gets stuck trying to double-write lock on SANSSensitivityCorrection calling Load calling HFIRLoad.

My guess is that Load does NOT transmit the "child" parameter.

[Janik Zikovsky]

Refs #4752: make AlgorithmProxy pass-through 'child' setting

To fix SANS system tests

Changeset: 85724e66af676c36ea94e681040cdc37bc117758

[Martyn Gigg]

The system tests are no longer hanging. I can also confirm that this works as when I removed the child status of child algorithms in python things did hang.

[Stuart Campbell]

This ticket has been transferred to github issue ​5599