 # Regarding comm_reducer function

Hi Team,

I am briefly mentioning the one of the example I tried,

n = te.var(‘n’)

m = te.var(‘m’)

C= te.placeholder((n), name=‘C’)

A = te.placeholder((n, m),dtype=‘float32’, name=‘A’)

k = te.reduce_axis((0, m), name=‘k’)

comp = lambda a, b: a + b

init = lambda dtype : tvm.tir.const(0,dtype=dtype) ; This also accepts functions min and max

product = te.comm_reducer(comp, init)

B = te.compute((n,), lambda i: product(A[i, k],axis=k), name=‘B’)

s = te.create_schedule(B.op)

print(tvm.lower(s, [A, B],simple_mode=True))

Gives output

produce B {

for (i, 0, n) {

``````B[(i*stride)] = 0f

for (k, 0, m) {

B[(i*stride)] = (B[(i*stride)] + A[((i*stride) + (k*stride))])

}
``````

}

}

Instead of 0f in the above example i am trying to initialize with C[i] by changing the init statement

init = lambda i: (C[i],‘float32’)

some part of Debug output

File “…/…/check/reduce.py”, line 64, in B = te.compute((n,), lambda i: product(A[i, k],axis=k), name=‘B’)

File “/local/mnt/workspace/gpk/nnv3/tvm/python/tvm/tir/op.py”, line 937, in reducer return _make_reduce(expr, axis, where)

File “/local/mnt/workspace/gpk/nnv3/tvm/python/tvm/tir/op.py”, line 924, in _make_reduce id_elem = convert(id_elem)

File “/local/mnt/workspace/gpk/nnv3/tvm/python/tvm/runtime/object_generic.py”, line 98, in convert return convert_to_object(value)

And gives the following error

[bt] (1) /local/mnt/workspace/gpk/nnv3/tvm/install/lib/libtvm.so(tvm::tir::CallNode::make(tvm::runtime::DataType, std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator >, tvm::Array<tvm::PrimExpr, void>, tvm::tir::CallNode::CallType, tvm::tir::FunctionRef, int)+0x2f4) [0x7fd8c427a394] [bt] (0) /local/mnt/workspace/gpk/nnv3/tvm/install/lib/libtvm.so(dmlc::LogMessageFatal::~LogMessageFatal()+0x3f) [0x7fd8c3d53a7f] File “/local/mnt/workspace/gpk/nnv3/tvm/src/tir/ir/expr.cc”, line 258 TVMError: Check failed: args[i].dtype().is_int():

Also, I doubt I am missing some information that needs to passed on compute statement with respect to the init statement change.

init = lambda i,dtype (C[i],dtype=dtype)  Gives invalid syntax error

Also tried just if a variable ‘p’ can be initialized as well.

1. comm_reducer function can handle only constant values as initial values?
2. Changing the convert() function inside make_reduce in python/tvm/tir/op.py will it allow any array to passed instead of constant value in comm_reducer?

Regards, Gayatri P K

Hello @tqchen,

Even I’m facing the problem described above.

I was checking this tutorial also. Based on my understanding comm_reducer function is not able to handle variable arrays as fidentity function should return a constant value. However, sometimes there will be a need to have variable values to be added to the output of matrix multiplication as shown in the below IR. This IR is not generated from any code, it’s just showing the desired use case:

``````  for (i: int32, 0, 512) {
for (j: int32, 0, 256) {
C_2[((i*256) + j)] = D[i]
for (K: int32, 0, 128) {
C_2[((i*256) + j)] = ((float32*)C_2[((i*256) + j)]) + ((float32*)A_2[((i*128) + K)])*(float32*)B_2[((K*256) + j)])))
}
}
}
``````

In the above IR, the initial value of C_2 is set as D[i] instead of 0. Here D[i] is another 1D array. Could you please help here ?