MATLAB: Integer strings decoding … speed optimization

MATLABsprintf

I have the following problem:
I need decode integer sequences "c" to char string messages "m" by following association:
numpos = 10 % ( = size(c,2)/2)
c = [3 4 1 1 4 2 5 2 3 3,1 1 1 1 2 2 2 3 3 3]
Each row of "c" represents 2*numpos integers, where first numpos parameters encoded position of
types = {'a' 'b@2' 'c@6' 'd@10' 'e@11'}
and second numpos parameters are applied only if type contains character '@' like this:
m = ' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'
My current solution is as follows:
function m = c2m(c,types)
numpos = size(c,2)/2;
F = cellfun(@(f) [' ' f], strrep(types,'@',':%d@'),'unif',0);
m = arrayfun(@(f,k) sprintf(f{1},k),F(c(:,1:numpos)),c(:,numpos+(1:numpos)),'unif', 0);
m = arrayfun(@(i) horzcat(m{i,:}), (1:numlines)', 'unif', 0)
end
and the testing code is as follows:
numlines = 10;
c = repmat([3 4 1 1 4 2 5 2 3 3,1 1 1 1 2 2 2 3 3 3],numlines,1);
types = {'a' 'b@2' 'c@6' 'd@10' 'e@11'};
m = c2m(c,types);
m =
    10×1 cell array
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
      {' c:1@6 d:1@10 a a d:2@10 b:2@2 e:2@11 b:3@2 c:3@6 c:3@6'}
The code is still too slow for me, I am looking for any speed up. In this case the most significant fraction of CPU time is spent at built-in function "sprintf".
Typical realistic sizes of problem are:
   numpos ~ 30 ... 60
   numlines ~ 1e4 ... 1e5
Any idea?

Best Answer

Probably fastest and simplest solution, I found so far ... using latest new Matlab (>= R2016b) features, see function insertBefore and string datatype.
function m = c2m(c,types) 
     types = string(types);
     numpos = size(c,2)/2;
     a = c(:,1:numpos);
     b = c(:,(numpos+1):end);
     m = types(a);
     m = insertBefore(m,"@", ":" + b);
     m = join(m,2);
 end
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