Unittests for SPDHG take long time

[paskino]

Unittests for SPDHG are done with the ASTRA cpu projector and on relatively large data, taking long time. We should reduce the amount of data that is processed.

CIL/Wrappers/Python/test/test_algorithms.py

Lines 757 to 770 in a2e45fe

	def test_SPDHG_vs_PDHG_implicit(self):
	data = dataexample.SIMPLE_PHANTOM_2D.get(size=(128,128))
	ig = data.geometry
	ig.voxel_size_x = 0.1
	ig.voxel_size_y = 0.1
	detectors = ig.shape[0]
	angles = np.linspace(0, np.pi, 90)
	ag = AcquisitionGeometry.create_Parallel2D().set_angles(angles,angle_unit='radian').set_panel(detectors, 0.1)
	# Select device
	dev = 'cpu'
	Aop = ProjectionOperator(ig, ag, dev)

[gfardell]

test_SPDHG_vs_PDHG_explicit and test_SPDHG_vs_PDHG_implicit
are particularly slow. The assert_almost_equal on such a large array is probably one of the biggest costs.

[MargaretDuff]

Thanks Gemma - have added this comment to #1644 PR which attempted to fix the slow tests

[MargaretDuff]

Closed by #1898