replace function in tall array. This indicates an internal error. Please contact MathWorks Technical Support.

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Peng Li
Peng Li on 25 Mar 2020
Commented: Sean de Wolski on 31 Mar 2020
I'm trying to replace a bunch of strings with meaningful strings in each column of a tall array. In the reference for replace function, it says it fully supports tall array. But I ran into the error. See an example below:
b = ["a", "6", "1001", "0", "3"]';
b = [b; b];
code = ["a"; "1001"; "3"; "10"];
meaning = ["atest", "1001t", "3b", "102b"]';
a2 = replace(b, code, meaning); % this works fine
a = replace(tall(b), code, meaning); % this throws an error
a1 = replace(tall(b'), code, meaning); % this throws another error asking me to contact technical support
first error message:
Error using tall/replace (line 21)
Incompatible tall array arguments. The first dimension in each tall array must have the same size, or have a size of
1.
It seems it complains about the tall(b) because the first dimension is not 1. So I explicitely transposed it by tall(b'), it threw the error below:
Error using tall/replace (line 21)
The operation generated an invalid chunk for output parameter 1. The chunk has size [1 10] where the expected size is
[4 10]. This indicates an internal error. Please contact MathWorks Technical Support.
I'm using R2020a.
  2 Comments
Peng Li
Peng Li on 30 Mar 2020
thanks Sean. yeah my goal is to write the tall table to disk after replacing all 500k*60k with specific meanings. Do you mean that if I gather here, it doesn't need the entire array to be in memory?
Yeah I used write to write this tall table to disk, and it then comes to my previous question actually which I think you also kindly replied lol

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Answers (2)

Jyotsna Talluri
Jyotsna Talluri on 30 Mar 2020
You have to use gather function to calulate the unevaluated tall array tall(b)
a2 = replace(b, code, meaning);
a = replace(gather(tall(b)), code, meaning);
Refer to the documentation link for more details
  1 Comment
Peng Li
Peng Li on 30 Mar 2020
Thanks Jyotsna. Unfortunately, i've a 500k*60k table. If I would gather it here, why do I bother using a tall table?

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Sean de Wolski
Sean de Wolski on 30 Mar 2020
Edited: Sean de Wolski on 30 Mar 2020
At the very least it's a doc bug because the doc says that tall arrays are fully supported for replace. It does appear to work with scalar values for old and new but the results are not the same because the replace happens sequentially rather than in one shot.
I'd contact tech support for that.
However, using categorical and renamecats, I'm able to get the same result:
b = ["a", "6", "1001", "0", "3"]';
b = [b; b];
code = ["a"; "1001"; "3"; "10"];
meaning = ["atest", "1001t", "3b", "102b"]';
a2 = replace(b, code, meaning); % this works fine
tb = tall(categorical(b, unique([code;b])));
b2 = renamecats(tb,code, meaning);
bg = gather(b2); % DON'T Call this, just doing it on simple example to check.
assert(isequal(string(bg), a2))
write('test.csv', b2); % Change the pattern to what you want for writing
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