In terms of exact numbers, hard drives support somewhere around 140MB/sec of sequential reads/writes, but only 120I/O’s/sec when doing reads/writes on random 4KB chunks. This is because the disk must physically spin to the read/write location. RAM supports somewhere around 5-10GB/sec of reads/writes, with much less penalty for random access. SSDs/Flash is somewhere in the middle, but with the i...

This is sometimes called the Netflix problem. A motivation for the matrix completion problem comes from user ratings of some products which are put into a matrix M . The entries Mij of the matrix correspond to the j’th user’s rating of product i. We assume that there exists an ideal matrix that encodes the ratings of all the products by all the users. However, it is not possible to ask every us...

Pablo Serra, Sabre Kais, and Nimrod Moiseyev Facultad de Matemática, Astronomı́a y Fı́sica, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 Department of Chemistry and the Minerva Center for Non-linear Physics of Complex Systems, Technion, Haifa 32000, Israel ~Received 22 January 2001; publish...