corrections chap1

[book_gpu.git] / BookGPU / Chapters / chapter2 / ch2.tex

diff --git a/BookGPU/Chapters/chapter2/ch2.tex b/BookGPU/Chapters/chapter2/ch2.tex
index a9e9a870ba5357a716553856f4f93383c4c60f9a..ae0704b99da0385b8e934d872795f131b465290c 100755 (executable)
--- a/BookGPU/Chapters/chapter2/ch2.tex
+++ b/BookGPU/Chapters/chapter2/ch2.tex
@@ -70,20 +70,20 @@ block.
 
 The Basic Linear Algebra Subprograms  (BLAS) allows programmer to use performant
 routines that are often used. Those routines are heavily used in many scientific
 
 The Basic Linear Algebra Subprograms  (BLAS) allows programmer to use performant
 routines that are often used. Those routines are heavily used in many scientific

-applications  and  are  very   optimzed  for  vector  operations,  matrix-vector
+applications  and  are  very   optimized  for  vector  operations,  matrix-vector

 operations                           and                           matrix-matrix
 operations                           and                           matrix-matrix

-operations~\cite{ch2:journals/ijhpca/Dongarra02}. Some of those operations seems
+operations~\cite{ch2:journals/ijhpca/Dongarra02}. Some of those operations seem

 to be  easy to  implement with CUDA.   Nevertheless, as  soon as a  reduction is
 needed, implementing an efficient reduction routines with CUDA is far from being
 simple.
 
 In this second example, we consider that  we have two vectors $A$ and $B$. First
 to be  easy to  implement with CUDA.   Nevertheless, as  soon as a  reduction is
 needed, implementing an efficient reduction routines with CUDA is far from being
 simple.
 
 In this second example, we consider that  we have two vectors $A$ and $B$. First

-of all we want to compute the sum  of both vectors in a vector $C$. Then we want
+of all, we want to compute the sum  of both vectors in a vector $C$. Then we want

 to compute the  scalar product between $1/C$ and $1/A$. This  is just an example
 to compute the  scalar product between $1/C$ and $1/A$. This  is just an example

-which has not direct interest except to show how to program it with CUDA.
+which has no direct interest except to show how to program it with CUDA.

 
 Listing~\ref{ch2:lst:ex2} shows this example with CUDA. The first kernel for the
 
 Listing~\ref{ch2:lst:ex2} shows this example with CUDA. The first kernel for the

-addition  of two  arrays  is exactly  the same  that  the one  described in  the
+addition  of two  arrays  is exactly  the same  as  the one  described in  the

 previous example.
 
 The  kernel  to  compute the  inverse  of  the  elements  of  an array  is  very
 previous example.
 
 The  kernel  to  compute the  inverse  of  the  elements  of  an array  is  very


@@ -91,14 +91,20 @@ simple. For  each thread index,  the inverse of  the array replaces  the initial
 array.
 
 In the main function,  the beginning is very similar to the  one in the previous
 array.
 
 In the main function,  the beginning is very similar to the  one in the previous

-example.   First the  number of  elements is  asked to  the user.   Then  a call
+example.   First, the number  of elements  is asked  to the  user.  Then  a call

 to \texttt{cublasCreate} allows to initialize  the cublas library. It creates an
 handle. Then all the arrays are allocated  in the host and the device, as in the
 previous  example.  Both  arrays  $A$ and  $B$  are initialized.   Then the  CPU
 computation is performed  and the time for this CPU  computation is measured. In
 order to  compute the same result  on the GPU, first  of all, data  from the CPU
 need to be  copied into the memory of  the GPU. For that, it is  possible to use
 to \texttt{cublasCreate} allows to initialize  the cublas library. It creates an
 handle. Then all the arrays are allocated  in the host and the device, as in the
 previous  example.  Both  arrays  $A$ and  $B$  are initialized.   Then the  CPU
 computation is performed  and the time for this CPU  computation is measured. In
 order to  compute the same result  on the GPU, first  of all, data  from the CPU
 need to be  copied into the memory of  the GPU. For that, it is  possible to use

-cublas function \texttt{cublasSetVector}.
+cublas function \texttt{cublasSetVector}.  This function several arguments. More
+precisely, the first argument represents the number of elements to transfer, the
+second arguments is the size of  each elements, the third element represents the
+source of the  array to transfer (in  the GPU), the fourth is  an offset between
+each element of  the source (usually this value  is set to 1), the  fifth is the
+destination (in the GPU)  and the last is an offset between  each element of the
+destination.

 
 \lstinputlisting[label=ch2:lst:ex2,caption=A simple example]{Chapters/chapter2/ex2.cu}
 
 
 \lstinputlisting[label=ch2:lst:ex2,caption=A simple example]{Chapters/chapter2/ex2.cu}