Apparatus, method, and computer program for collecting diagnostic information

An apparatus 2 has processing circuitry such as vector processing 22 or matrix processing 24 circuitry to perform single instruction, multiple data (SIMD) processing on an array with a plurality of data items, and the processing circuitry supports the SIMD processing for a plurality of array sizes 62, 64. The processing circuitry is able to select an array size with which to perform the SIMD processing based on SIMD processing configuration information 66. Diagnostic information collection circuitry 60 is provided to collect diagnostic information about software executing on the processing circuitry and the diagnostic information collection circuitry filters or suppresses collection of the diagnostic information based on the SIMD processing configuration information (e.g. Figure 7).