cyb70289 commented on a change in pull request #9841:
URL: https://github.com/apache/arrow/pull/9841#discussion_r604553475
##########
File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
##########
@@ -233,6 +235,282 @@ struct DivideChecked {
}
};
+struct Power {
+ template <typename T, typename Arg0, typename Arg1>
+ static enable_if_signed_integer<T> Call(KernelContext* ctx, Arg0 left, Arg1
right) {
+ Arg0 result = 1;
+ if (left == 0) {
+ if (right < 0) {
+ ARROW_PREDICT_FALSE(MultiplyWithOverflow(2,
std::numeric_limits<Arg0>::max(), &result));
+ ctx->SetStatus(Status::Invalid("divide by zero"));
+ return result;
+ } else if (right == 0) {
+ return 1;
+ }
+ return 0;
+ } else if (right == INFINITY && abs(left) > 1) {
+ ARROW_PREDICT_FALSE(MultiplyWithOverflow(2,
std::numeric_limits<Arg0>::max(), &result));
+ return result;
+ } else if (right == -INFINITY && abs(left) > 1) {
+ return 0;
+ }
Review comment:
I don't see why it's so complicated. This function is only for integer
power, all args are supposed to be integers (see checked version). So there
will be no things like `infinity`, which is only for floating points. I think
just verify that the exponent is non-negtive should be enough.
##########
File path: cpp/src/arrow/compute/kernels/scalar_arithmetic.cc
##########
@@ -233,6 +235,282 @@ struct DivideChecked {
}
};
+struct Power {
+ template <typename T, typename Arg0, typename Arg1>
+ static enable_if_signed_integer<T> Call(KernelContext* ctx, Arg0 left, Arg1
right) {
+ Arg0 result = 1;
+ if (left == 0) {
+ if (right < 0) {
+ ARROW_PREDICT_FALSE(MultiplyWithOverflow(2,
std::numeric_limits<Arg0>::max(), &result));
+ ctx->SetStatus(Status::Invalid("divide by zero"));
+ return result;
+ } else if (right == 0) {
+ return 1;
+ }
+ return 0;
+ } else if (right == INFINITY && abs(left) > 1) {
+ ARROW_PREDICT_FALSE(MultiplyWithOverflow(2,
std::numeric_limits<Arg0>::max(), &result));
+ return result;
+ } else if (right == -INFINITY && abs(left) > 1) {
+ return 0;
+ }
+
+ if (right > 0) {
+ for (Arg1 i = 0; i < right; i++) {
+ if (ARROW_PREDICT_FALSE(MultiplyWithOverflow(result, left, &result))) {
+ ctx->SetStatus(Status::Invalid("overflow"));
+ }
+ }
+ } else {
+ for (Arg1 i = 0; i < -right; i++) {
Review comment:
Again, negative exponent is illegal for integer power. This function is
returning T, which is an integer.
We'd better reference implementations from other software first, e.g.,
https://numpy.org/doc/stable/reference/generated/numpy.power.html
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