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`for`-loop over distributed range

for= drange(variable) statement ... statement endcolonop

The general format is

for= drange(variable) statement ... statement endcolonop

The `colonop` is an expression of the form `start:increment:finish` or `start:finish`.
The default value of increment is 1. The `colonop` is
partitioned by `codistributed.colon` into `numlabs` contiguous
segments of nearly equal length. Each segment becomes the iterator
for a conventional for-loop on an individual worker.

The most important property of the loop body is that each iteration
must be independent of the other iterations. Logically, the iterations
can be done in any order. No communication with other workers is
allowed within the loop body. The functions that perform communication
are `gop`, `gcat`, `gplus`, `codistributor`, `codistributed`, `gather`, and `redistribute`.

It is possible to access portions of codistributed arrays that are local to each worker, but it is not possible to access other portions of codistributed arrays.

The `break` statement
can be used to terminate the loop prematurely.

Find the rank of magic squares. Access only the local portion of a codistributed array.

r = zeros(1, 40, codistributor()); for n = drange(1:40) r(n) = rank(magic(n)); end r = gather(r);

Perform Monte Carlo approximation of pi. Each worker is initialized to a different random number state.

m = 10000; for p = drange(1:numlabs) z = rand(m, 1) + i*rand(m, 1); c = sum(abs(z) < 1) end k = gplus(c) p = 4*k/(m*numlabs);

Attempt to compute Fibonacci numbers. This will *not* work,
because the loop bodies are dependent.

f = zeros(1, 50, codistributor()); f(1) = 1; f(2) = 2; for n = drange(3:50) f(n) = f(n - 1) + f(n - 2) end

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