Matrix Multiplication (ch.21)

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In chapter 21, the example proposed is a "multiplication of A times B with the 
result added into C" (p.499)
This function is then presented as C = C + A * B throughout the chapter.

However, it seems to me that the presented code is actually doing C = A * B.

In listing 21.1 (p.500-501) the multiplication A*B is stored in tmp (which is 
initialized to 0.0). tmp is then copied into C(i,j) without taking in count 
it's initial value.
Also, in listing 21.3 (p.504-505) the C matrix is created as a 
CL_MEM_WRITE_ONLY memory object and is obviously not added in the queue before 
launching the kernel.

Original issue reported on code.google.com by [email protected] on 10 Oct 2012 at 10:10