Coder, randsample: Variable 'edges' is not fully defined on some execution paths.

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I'm trying to compile a Matlab code with the coder that calls randsample(n,k,true,w) for integers n and k and a weight-vector w. I get the error message, "Variable 'edges' is not fully defined on some execution paths." which seems to be a problem within the randsample function. Any ideas what to do without touching randsample.m itself? Thanks
Michael Hartmann
Michael Hartmann on 31 Jul 2018
Attached is the code that calls randsample, where the input is specified as
N = 3;
Mk = 10;
Mp = 10;
s_length = floor(200000);
x = 0.01*rand((N+1)*(Mk+Mp+1)*2,1);

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Accepted Answer

Mike Hosea
Mike Hosea on 31 Jul 2018
Edited: Mike Hosea on 31 Jul 2018
This is a bug in the code generation version of RANDSAMPLE. The compiler is complaining about a situation that it really doesn't need to complain about, as the edges variable is never referenced unless it is first defined as far as I can tell. It's just challenging to infer that from a static analysis.
I'll create an internal bug report for this to get it fixed. It's really just a matter of providing an initialization for edges even when w is empty (e.g. adding
edges = zeros('like',w);
before the "end" on line 66 of matlab/toolbox/stats/eml/randsample.m. I mean, that's completely unsupported, and I'm not recommending it. You'd be doing that at your own risk. Really. Who knows what might happen?).
Mike Hosea
Mike Hosea on 2 Aug 2018
Glad to hear it. FYI, 2018b development is currently past the point where we could reasonably slip this in. Just wanted you to know in case you upgrade to 18b and expect to see the fix there.

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More Answers (1)

Joel Fernandez
Joel Fernandez on 6 Aug 2018
Edited: Stephen23 on 6 Aug 2018
Hi everyone Can someone help me ? My code error is: "Variable 'sa' is not fully defined on some execution paths" So I'm using this code to SVPWM
function sf =aaa(u)
ts=0.0002;vdc=1;peak_phase_max= vdc/sqrt(3);
x=u(2); y=u(3);
mag=(u(1)/peak_phase_max) * ts;
%sector I
if (x>=0) & (x<pi/3)
ta = mag * sin(pi/3-x);
tb = mag * sin(x);
t0 =(ts-ta-tb);
t1=[t0/4 ta/2 tb/2 t0/2 tb/2 ta/2 t0/4];
v1=[0 1 1 1 1 1 0];
v2=[0 0 1 1 1 0 0];
v3=[0 0 0 1 0 0 0];
for j=1:7
sf=[sa, sb, sc];
  1 Comment
Stephen23 on 6 Aug 2018
Edited: Stephen23 on 6 Aug 2018
@Joel Fernandez: your code is badly aligned. Badly aligned code is one way that beginners hide bugs in their code. You should align your code using the default MATLAB editor settings. You can align the code: select all code, then click ctrl+i. It will give this:
function sf = aaa(u)
ts = 0.0002; vdc = 1; peak_phase_max = vdc / sqrt(3);
x = u(2); y = u(3);
mag = (u(1) / peak_phase_max) * ts;
%sector I
if (x >= 0) & (x < pi / 3)
ta = mag * sin(pi / 3 - x);
tb = mag * sin(x);
t0 = (ts - ta - tb);
t1 = [t0 / 4 ta / 2 tb / 2 t0 / 2 tb / 2 ta / 2 t0 / 4];
t1 = cumsum(t1);
v1 = [0 1 1 1 1 1 0];
v2 = [0 0 1 1 1 0 0];
v3 = [0 0 0 1 0 0 0];
for j = 1:7
if (y <= t1(j))
sa = v1(j);
sb = v2(j);
sc = v3(j);
sf = [sa, sb, sc];
This makes it clear that if x<0 or x>pi/3 or any of the y>t1 then sa, sb and sc will not be defined, thus the error message.
Note that using lots of superfluous whitepsace in this vector has made it unclear what it should contain:
[t0 / 4 ta / 2 tb / 2 t0 / 2 tb / 2 ta / 2 t0 / 4];
It is clearer to use commas instead of whitespace to separate the array elements, and to not use whitespace around operators, e.g.:
[t0/4, ta/2, tb/2, t0/2, tb/2, ta/2, t0/4];

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