zpf is a floating-point array primitive using very high-speed, lossy (but optionally error-bounded) compression to significantly reduce data volumes. zfp reduces I/O time and off-line storage requirements by 1-2 orders of magnitude depending on accuracy requirements, as dictated by user-set error tolerances. Unique among data compressors, zfp also supports constant-time read/write random access to individual array elements from compressed storage. zfp’s compressed arrays can often replace conventional arrays in existing applications with minimal code changes, allowing, for example, the user to store tables of floating-point data in compressed form that otherwise would not fit in memory. When used in numerical computations, zfp arrays provide a fine-grained knob on precision while achieving accuracy comparable to IEEE floating point at half the storage, reducing both memory usage and bandwidth.