broadcasting in af_arith for binary operations [WIP] #2871

syurkevi · 2020-05-05T01:14:56Z

Will prepend 1s until dimension sizes match, then 1s are treated as wildcards and are broadcasted to their matching sizes.

array A = range(dim4(32, 32, 3), 2);  // [32 32 3]
array B = -range(dim4(3)); //    [ 3 ] -> [1* 1* 3]

array C = A + B; // [32 32 3]

In cases where one of the arguments is a vector, prepending until dimensions match may not align well:

 array A = constant(-1, dim4(15, 3, 5)); // [15 3 5]
 array B = constant(1, dim4(3, 1));        // [ 1  1 3] - misaligned,
 // even though 3 intended to broadcast with second dimension of A

Upon a mismatch, the prepended vectors will be shifted left until there is a match. In the above example the broadcast will be a success after a single additional shift.

This manner of treating vectors is a workaround due to no difference between.

af::dim4 d1(3);
af::dim4 d2(3, 1);
af::dim4 d3(3, 1, 1);
af::dim4 d4(3, 1, 1, 1);
// d1 == d2 == d3 == d4

TODO:

n-ary operations?
complex values

9prady9 · 2020-05-14T12:27:35Z

src/api/c/binary.cpp

+    const dim4 ldims = linfo.dims();
+    const dim4 rdims = rinfo.dims();
+
+    unsigned maxndims =


unsigned maxndims = std::max(ldims.ndims(), rdims.ndims());

Would this break logic ?

9prady9 · 2020-05-14T12:27:35Z

src/api/c/binary.cpp

+    dim4 padded(1, 1, 1, 1);
+
+    const unsigned MAXDIMS = 4;
+    for (unsigned i = 0; i < MAXDIMS; ++i) {


MAXDIMS -> AF_MAX_DIMS

We can then remove this new constant MAXDIMS

9prady9 · 2020-05-14T12:27:35Z

src/api/c/binary.cpp

@@ -46,6 +48,96 @@ static inline af_array arithOp(const af_array lhs, const af_array rhs,
    return res;
 }

+dim4 paddims(const dim4 &dims, unsigned offset) {


paddims -> padDims to be consistent

9prady9 · 2020-05-14T12:27:35Z

src/api/c/binary.cpp

+    dim4 ltile(1, 1, 1, 1);
+    dim4 rtile(1, 1, 1, 1);
+    // check that dimensions are compatible
+    for (unsigned i = 0; i < 4; ++i) {


4 -> AF_MAX_DIMS

9prady9 · 2020-05-14T12:46:22Z

src/api/c/binary.cpp

+    detail::Array<T> lhst =
+        detail::tile<T>(modDims(getArray<T>(lhs), lpad), ltile);
+    detail::Array<T> rhst =
+        detail::tile<T>(modDims(getArray<T>(rhs), rpad), rtile);


Add using statements for the following to fit convention we are following in other files.

using detail::Array

using detail::tile

using std::tie

9prady9 · 2020-05-14T12:46:39Z

src/api/c/binary.cpp

+        detail::tile<T>(modDims(getArray<T>(rhs), rpad), rtile);
+
+    af_array res = getHandle(arithOp<T, op>(lhst, rhst, odims));
+    return res;


Above two lines can be clubbed.

umar456 · 2022-04-04T23:38:36Z

test/array.cpp

@@ -582,3 +582,69 @@ TEST(Array, InitializerListAndDim4) {

    ASSERT_ARRAYS_EQ(A, B);
 }
+
+TEST(Broadcast, Simple1) {


Can you create parameterized tests for the input dims? You also want to compare this functionality to the tiled version of the same operation. Additionally you should make sure that the kernels generated and the operations performed by these functions are what you expect.

syurkevi added 2 commits May 5, 2020

initial simple broadcasting in af_arith for binary operations

3f91d15

fixes memory leaks

8471d80

9prady9 reviewed May 14, 2020

View changes

umar456 reviewed Apr 4, 2022

View changes

arrayfire / arrayfire Public

broadcasting in af_arith for binary operations [WIP] #2871

broadcasting in af_arith for binary operations [WIP] #2871

syurkevi commented May 5, 2020

9prady9 May 14, 2020

9prady9 May 14, 2020

9prady9 May 14, 2020

9prady9 May 14, 2020

9prady9 May 14, 2020

9prady9 May 14, 2020

umar456 Apr 4, 2022

arrayfire / arrayfire Public

broadcasting in af_arith for binary operations [WIP] #2871

Are you sure you want to change the base?

broadcasting in af_arith for binary operations [WIP] #2871

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