damianmoz
commented
1 year ago I think you have found a simplification of a problem I have seen. Consider this partial reduction
proc partial
{
var A : [1..8, 1..8] real;
var x : [1..8] real;
for i in 1..8 do // fill A with some data
{
for j in 1..8 do
{
A[i, j] = (4 - i):real + ((5 - j) * 2):real;
}
}
x = + scan (A[1, ..]); // likewise with 'x'
writeln(x);
// 3 IMPORTANT LINES
const u = + reduce [i in 1..8] x[i] * A[i, ..]; // partial reduction
var y : [1..8] real = 0.0; // build reduction using reduction intent
var z = y; // build reduction into 'z' manually
for r in 1..8 do
z += x[r] * A[r, ..];
[ (r, c) in A.domain with (+ reduce y) ] y[c] += x[r] * A[r, c];
writeln('partial reduction:');
writeln('- manual: ', z);
writeln('- intent: ', y);
writeln('- direct: ', u);
}This crashes with the error
m.chpl:16: error: halt reached - argument to ! is nilMoving the partial reduction two lines down within the THREE IMPORTANT LINES and the identical reduction code now works!
var y : [1..8] real = 0.0; // build reduction using reduction intent
var z = y; // build reduction into 'z' manually
const u = + reduce [i in 1..8] x[i] * A[i, ..]; // partial reductionOr removing from the reduction the complexity of the scalar multiplication of the row of the matrix also works!!
inline proc row(m, v) return m * v;
const u = + reduce [r in 1..8] row(x[r], A[r, ..]); // partial reduction
var y : [1..8] real = 0.0; // build reduction using reduction intent
var z = y; // build reduction into 'z' manuallyYou have a slightly different test case to help you track down (and correct) what looks like much the same bug.
I suggest you try the code with the same (later) version of the compiler that you are using. I have vanilla 1.29.0 with clang14.
cassella
vasslitvinov
bradcray
lydia-duncan
Summary of Problem
The code below nondeterministically attempts to dereference nil, or hits a LocaleModel error, or just segfaults.
Some of the other variants hit just the dereference nil error, or even work, as noted.
Modifying the code to pick one of the variants based on a config var makes the problem go away.
Steps to Reproduce
Source Code:
Execution command:
[edit: this is repeated invocation of the same binary. ]
Associated Future Test(s):
test/parallel/taskPar/nested/forall-with-continue-forall-bracket-expr.chpl#21411test/parallel/taskPar/nested/forall-with-continue-forall-expr.chpl#21411test/parallel/taskPar/nested/forall-with-continue-reduction-over-forall-bracket-expr.chpl#21411Configuration Information
This is with
CHPL_COMM=nonefor clarity. It also hit the problem withCHPL_COMM=gasnet.