Node mriqc.interfaces.functional.Spikes is a memory hog

[oesteban]

This node in the workflow

mriqc/mriqc/workflows/functional/output.py

Lines 95 to 100 in d5b13cb

	spikes_bg = pe.MapNode(
	Spikes(no_zscore=True, detrend=False),
	name='SpikesFinderBgMask',
	mem_gb=mem_gb * 2.5,
	iterfield=['in_file', 'in_mask'],
	)

often causes memory errors.

In a quick review, I believe casting here

mriqc/mriqc/interfaces/functional.py

Line 229 in d5b13cb

func_data = func_nii.get_fdata()

to float32 would be safe and have zero effects on the interface performance.