One way to reduce the memory requriement is to calculate the 3c2e ERI in batches (first apply schwarz screening for the batch to find offsets and all and then evaluate the 3c2e ERI). After the batch is computed, see if there are still some close to zero elements and get rid of those and thus compress the array further. Offsets or any indices arrays will need to be updated accordingly.
One way to reduce the memory requriement is to calculate the 3c2e ERI in batches (first apply schwarz screening for the batch to find offsets and all and then evaluate the 3c2e ERI). After the batch is computed, see if there are still some close to zero elements and get rid of those and thus compress the array further. Offsets or any indices arrays will need to be updated accordingly.