To improve the execution speed of code generated for certain low-level vector and matrix operations (such as matrix multiplication), MATLAB® Coder™ can generate calls to BLAS functions instead of generating code for these operations. BLAS is a software library for low-level vector and matrix computations that has several highly optimized machine-specific implementations. MATLAB Coder uses the CBLAS C interface to BLAS.
For MEX generation, if the input arrays for the matrix functions meet certain criteria, the code generator produces BLAS calls. For standalone code (library or executable program), by default, the code generator does not produce BLAS calls. If you specify that you want to generate BLAS calls, and the input arrays for the matrix functions meet the criteria, the code generator produces BLAS calls.
For MEX functions, the code generator uses the BLAS library that is included with MATLAB. For standalone code, the code generator uses the BLAS library that you specify. See Speed Up Matrix Operations in Generated Standalone Code by Using BLAS Calls.