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Here are two excellent books for your learning pleasure:
OpenCL.Programming.Guide.Jul.2011.pdf:
https://mega.nz/#!BpkDhYCS!oubpkHbhUzPEJq-65TgV4z0HNF1ijlTgJzDvNNe1pmE
and
Tsuchiyama-The OpenCL Programming Book_2010.pdf:
https://mega.nz/#!QwdADAwS!web917oDLriQE-jXbFHbEMTBaiFasm6nHqsVqoHa8B8