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AnswerRe: MFC DDX_Radio causes debug assertion failure when DoDataExchange is called Pin
Victor Nijegorodov30-Mar-18 3:34
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GeneralRe: MFC DDX_Radio causes debug assertion failure when DoDataExchange is called Pin
janaswamy uday30-Mar-18 4:37
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GeneralRe: MFC DDX_Radio causes debug assertion failure when DoDataExchange is called Pin
Victor Nijegorodov30-Mar-18 6:29
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GeneralRe: MFC DDX_Radio causes debug assertion failure when DoDataExchange is called Pin
janaswamy uday30-Mar-18 7:42
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GeneralRe: MFC DDX_Radio causes debug assertion failure when DoDataExchange is called Pin
Richard Andrew x6430-Mar-18 15:11
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SuggestionRe: MFC DDX_Radio causes debug assertion failure when DoDataExchange is called Pin
Jochen Arndt30-Mar-18 22:17
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GeneralRe: MFC DDX_Radio causes debug assertion failure when DoDataExchange is called Pin
janaswamy uday1-Apr-18 21:05
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QuestionHow to map a matrix index to a memory location Pin
Leif Simon Goodwin29-Mar-18 1:26
memberLeif Simon Goodwin29-Mar-18 1:26 
We have a device that returns data from a 2D grid thus each data value is indexed by its row and column. The number of rows and columns is not fixed, as the device can be reconfigured, but in normal use the number of rows and columns does not change. We store the data values in memory for subsequent retrieval.

Our problem is how to convert a row + column pair {x,y} into an address in the memory. This sounds trivial:

offset = x * (total_number_of_columns) + y;

However, we have to do this very very quickly, and using as little processor power as possible. A multiplication is not good. We do not need to store the values contiguously as row, row, row etc. We do have limited memory so cannot be too wasteful.

One way is to store the data values in a grid whose number of columns is always a power of 2. Thus if our device generates 20 rows and 50 columns of data, we store them in a 20 rows by 64 columns grid. This means the data is not packed tightly in memory. To convert {x,y} into a memory location:

offset = x << 6 + y;

The quickest way I can think of is to use a look up table:

offset = lookup[x] + y;

Thus lookup is the offset to the start of each row in memory.

So, my question is how can we do this as fast and simply as possible? Is there a quicker way?
AnswerRe: How to map a matrix index to a memory location Pin
Jochen Arndt29-Mar-18 2:39
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GeneralRe: How to map a matrix index to a memory location Pin
Leif Simon Goodwin29-Mar-18 3:12
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GeneralRe: How to map a matrix index to a memory location Pin
harold aptroot29-Mar-18 3:44
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AnswerRe: How to map a matrix index to a memory location Pin
Daniel Pfeffer29-Mar-18 5:06
professionalDaniel Pfeffer29-Mar-18 5:06 
QuestionWhat is the best tool to find C++ Memory issues Pin
ptr_Electron29-Mar-18 1:06
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AnswerRe: What is the best tool to find C++ Memory issues Pin
Leif Simon Goodwin29-Mar-18 1:28
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GeneralRe: What is the best tool to find C++ Memory issues Pin
ptr_Electron30-Mar-18 10:12
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QuestionMemory allocated out side of try and Delete in finally Pin
ptr_Electron28-Mar-18 23:46
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AnswerRe: Memory allocated out side of try and Delete in finally Pin
Jochen Arndt29-Mar-18 0:17
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GeneralRe: Memory allocated out side of try and Delete in finally Pin
ptr_Electron29-Mar-18 1:05
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GeneralRe: Memory allocated out side of try and Delete in finally Pin
Jochen Arndt29-Mar-18 1:44
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Questionerror C2143: syntax error: missing ':' before 'constant' Pin
ForNow27-Mar-18 15:53
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QuestionRe: error C2143: syntax error: missing ':' before 'constant' Pin
David Crow27-Mar-18 16:47
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AnswerRe: error C2143: syntax error: missing ':' before 'constant' Pin
ForNow27-Mar-18 16:52
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GeneralRe: error C2143: syntax error: missing ':' before 'constant' Pin
Peter_in_278027-Mar-18 18:13
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GeneralRe: error C2143: syntax error: missing ':' before 'constant' Pin
ForNow28-Mar-18 14:50
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GeneralRe: error C2143: syntax error: missing ':' before 'constant' Pin
Victor Nijegorodov27-Mar-18 21:18
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