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→Matrix multiplication: Generalizing matrix multiplication example which employs blocking. |
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On a year 2014 processor, the second case is approximately five times faster than the first case, when written in [[C (programming language)|C]] and compiled with <code>gcc -O3</code>. (A careful examination of the disassembled code shows that in the first case, [[GNU Compiler Collection|GCC]] uses [[SIMD]] instructions and in the second case it does not, but the cache penalty is much worse than the SIMD gain.){{Citation needed|date=September 2014}}
Temporal locality can also be improved in the above example by using a technique called [[Loop blocking|blocking]]. The larger matrix can be divided into evenly sized sub-matrices, so that the smaller blocks can be referenced (multiplied) several times while in memory. Note that this example works for square matrices of dimensions SIZE x SIZE, but it can easily be extended for arbitrary matrices by substituting SIZE_I, SIZE_J and SIZE_K where appropriate.
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