[BUG] Memory Leak in SVM

[harrism]

Describe the bug
There are allocations with no matching deallocation in svm/sparse_util.cuh.

cuml/cpp/src/svm/sparse_util.cuh

Lines 766 to 778 in 973a65f

	*indptr_out = (int*)rmm_alloc->allocate((num_indices + 1) * sizeof(int), stream);
	*nnz = computeIndptrForSubset(indptr_in, *indptr_out, row_indices, num_indices, stream);
	// allocate indices, data
	*indices_out = (int*)rmm_alloc->allocate(*nnz * sizeof(int), stream);
	*data_out = (math_t*)rmm_alloc->allocate(*nnz * sizeof(math_t), stream);
	// copy with 1 warp per row for now, blocksize 256
	const dim3 bs(32, 8, 1);
	const dim3 gs(raft::ceildiv(num_indices, (int)bs.y), 1, 1);
	extractCSRRowsFromCSR<math_t><<<gs, bs, 0, stream>>>(
	*indptr_out, *indices_out, *data_out, indptr_in, indices_in, data_in, row_indices, num_indices);

Steps/Code to reproduce bug

Inspect the linked code.

Expected behavior

See #5852. There should be no raw calls to resource::allocate(). Instead, use device containers like device_buffer.

[mfoerste4]

@harrism , this utility function is used to extract the support vectors and pass them back to the python world. The reason for the plain allocation is that here - just like for the dense counterpart - we don't know the dimensions in advance and therefore cannot allocate the stores from python in advance. The allocations are not really leaking as long as the new owner takes care of destruction.

AFAIK there are no data-owning containers exposed to python that would allow to be resized later on (please correct me if I am wrong or that changed). We would need something like a device_buffer representation on python side for this. If the allocation needs to be removed I would appreciate guidance on how this should be accomplished.

CC @tfeher , @divyegala

[divyegala]

@mfoerste4 RMM has a python-side device_buffer object https://github.com/rapidsai/rmm/blob/branch-24.10/python/rmm/rmm/_lib/device_buffer.pyx

Would this suffice? It has resizing available.

[mfoerste4]

Thanks @divyegala , I was not aware that we can use these right away. I will see whether it is much effort to replace it.