tqchen commented on a change in pull request #5289: add tensorflow cumsum
URL: https://github.com/apache/incubator-tvm/pull/5289#discussion_r407139910
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File path: topi/include/topi/transform.h
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@@ -1105,6 +1105,88 @@ inline tvm::te::Tensor matmul(const tvm::te::Tensor& A,
return tvm::te::compute(output_shape, l, name, tag);
}
+/**
+ * Compute the cumulative sum of the tensor `A` along `axis`.
+ *
+ * By default, this operation performs an inclusive cumsum, which means that
the first
+ * element of the input is identical to the first element of the output:
+ *
+ * ```python
+ * cumsum([a, b, c]) # [a, a + b, a + b + c]
+ * ```
+ *
+ * By setting the `exclusive` kwarg to `True`, an exclusive cumsum is
performed
+ * instead:
+ *
+ * ```python
+ * cumsum([a, b, c], exclusive=True) # [0, a, a + b]
+ * ```
+ *
+ * By setting the `reverse` kwarg to `True`, the cumsum is performed in the
+ * opposite direction:
+ *
+ * ```python
+ * cumsum([a, b, c], reverse=True) # [a + b + c, b + c, c]
+ * ```
+ *
+ * The `reverse` and `exclusive` kwargs can also be combined:
+ *
+ * ```python
+ * cumsum([a, b, c], exclusive=True, reverse=True) # [b + c, c, 0]
+ * ```
+ *
+ * @param A Input tensor
+ * @param axis Must be in the range `[-rank(x), rank(x))`
+ * @param exclusive Perform exclusive cumsum
+ * @param reverse Performed in the opposite direction
+ * @param name The name of the operation
+ * @param tag The tag to mark the operation
+ * @return A Tensor whose op member is the cumsum operation
+ */
+inline tvm::te::Tensor cumsum(const tvm::te::Tensor& A,
+ int axis,
+ bool exclusive = false,
+ bool reverse = false,
+ std::string name = "T_cumsum",
+ std::string tag = kCumsum) {
+ int totalSize = static_cast<int>(A->shape.size());
+ if (axis < 0) {
+ axis = totalSize + axis;
+ }
+ auto maxLength = A->shape[axis];
+ auto l = [&](const Array<Var>& input_indices) {
Review comment:
This way of implementing cumsum would cost additional compute, since we are
doing reduction in parallel without reuse, can we use scan instead?
https://tvm.apache.org/docs/tutorials/language/scan.html
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