wesm commented on a change in pull request #7531: URL: https://github.com/apache/arrow/pull/7531#discussion_r445122603
########## File path: cpp/src/arrow/util/spaced.h ########## @@ -0,0 +1,199 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +#pragma once + +#include "arrow/util/align_util.h" +#include "arrow/util/bit_block_counter.h" +#include "arrow/util/bitmap_reader.h" + +namespace arrow { +namespace util { +namespace internal { + +/// \brief Compress the buffer to spaced, excluding the null entries. +/// +/// \param[in] src the source buffer +/// \param[in] num_values the size of source buffer +/// \param[in] valid_bits bitmap data indicating position of valid slots +/// \param[in] valid_bits_offset offset into valid_bits +/// \param[out] output the output buffer spaced +/// \return The size of spaced buffer. +template <typename T> +inline int SpacedCompress(const T* src, int num_values, const uint8_t* valid_bits, + int64_t valid_bits_offset, T* output) { + int num_valid_values = 0; + int idx_src = 0; + + const auto p = + arrow::internal::BitmapWordAlign<1>(valid_bits, valid_bits_offset, num_values); + // First handle the leading bits + const int leading_bits = static_cast<int>(p.leading_bits); + while (idx_src < leading_bits) { + if (BitUtil::GetBit(valid_bits, valid_bits_offset)) { + output[num_valid_values] = src[idx_src]; + num_valid_values++; + } + idx_src++; + valid_bits_offset++; + } + + // The aligned parts scaned with BitBlockCounter Review comment: typo: scanned ########## File path: cpp/src/arrow/util/spaced.h ########## @@ -0,0 +1,199 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +#pragma once + +#include "arrow/util/align_util.h" +#include "arrow/util/bit_block_counter.h" +#include "arrow/util/bitmap_reader.h" + +namespace arrow { +namespace util { +namespace internal { + +/// \brief Compress the buffer to spaced, excluding the null entries. +/// +/// \param[in] src the source buffer +/// \param[in] num_values the size of source buffer +/// \param[in] valid_bits bitmap data indicating position of valid slots +/// \param[in] valid_bits_offset offset into valid_bits +/// \param[out] output the output buffer spaced +/// \return The size of spaced buffer. +template <typename T> +inline int SpacedCompress(const T* src, int num_values, const uint8_t* valid_bits, + int64_t valid_bits_offset, T* output) { + int num_valid_values = 0; + int idx_src = 0; + + const auto p = + arrow::internal::BitmapWordAlign<1>(valid_bits, valid_bits_offset, num_values); + // First handle the leading bits + const int leading_bits = static_cast<int>(p.leading_bits); + while (idx_src < leading_bits) { + if (BitUtil::GetBit(valid_bits, valid_bits_offset)) { + output[num_valid_values] = src[idx_src]; + num_valid_values++; + } + idx_src++; + valid_bits_offset++; + } + + // The aligned parts scaned with BitBlockCounter + arrow::internal::BitBlockCounter data_counter(valid_bits, valid_bits_offset, + num_values - leading_bits); + auto current_block = data_counter.NextWord(); + while (idx_src < num_values) { + if (current_block.AllSet()) { // All true values + int run_length = 0; + // Scan forward until a block that has some false values (or the end) + while (current_block.length > 0 && current_block.AllSet()) { + run_length += current_block.length; + current_block = data_counter.NextWord(); + } + // Fill all valid values of this scan + std::memcpy(&output[num_valid_values], &src[idx_src], run_length * sizeof(T)); + num_valid_values += run_length; + idx_src += run_length; + valid_bits_offset += run_length; + // The current_block already computed, advance to next loop + continue; + } else if (!current_block.NoneSet()) { // Some values are null + arrow::internal::BitmapReader valid_bits_reader(valid_bits, valid_bits_offset, + current_block.length); + for (int64_t i = 0; i < current_block.length; i++) { + if (valid_bits_reader.IsSet()) { + output[num_valid_values] = src[idx_src]; + num_valid_values++; + } + idx_src++; + valid_bits_reader.Next(); + } + valid_bits_offset += current_block.length; + } else { // All null values + idx_src += current_block.length; + valid_bits_offset += current_block.length; + } + current_block = data_counter.NextWord(); + } + + return num_valid_values; +} + +/// \brief Expand the buffer but leave spaces for null entries. Review comment: Maybe "Relocate values in buffer into positions of non-null values as indicated by a validity bitmap"? ########## File path: cpp/src/arrow/util/spaced.h ########## @@ -0,0 +1,199 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +#pragma once + +#include "arrow/util/align_util.h" +#include "arrow/util/bit_block_counter.h" +#include "arrow/util/bitmap_reader.h" + +namespace arrow { +namespace util { +namespace internal { + +/// \brief Compress the buffer to spaced, excluding the null entries. +/// +/// \param[in] src the source buffer +/// \param[in] num_values the size of source buffer +/// \param[in] valid_bits bitmap data indicating position of valid slots +/// \param[in] valid_bits_offset offset into valid_bits +/// \param[out] output the output buffer spaced +/// \return The size of spaced buffer. +template <typename T> +inline int SpacedCompress(const T* src, int num_values, const uint8_t* valid_bits, + int64_t valid_bits_offset, T* output) { + int num_valid_values = 0; + int idx_src = 0; + + const auto p = + arrow::internal::BitmapWordAlign<1>(valid_bits, valid_bits_offset, num_values); + // First handle the leading bits + const int leading_bits = static_cast<int>(p.leading_bits); + while (idx_src < leading_bits) { + if (BitUtil::GetBit(valid_bits, valid_bits_offset)) { + output[num_valid_values] = src[idx_src]; + num_valid_values++; + } + idx_src++; + valid_bits_offset++; + } + + // The aligned parts scaned with BitBlockCounter + arrow::internal::BitBlockCounter data_counter(valid_bits, valid_bits_offset, + num_values - leading_bits); + auto current_block = data_counter.NextWord(); + while (idx_src < num_values) { + if (current_block.AllSet()) { // All true values + int run_length = 0; + // Scan forward until a block that has some false values (or the end) + while (current_block.length > 0 && current_block.AllSet()) { + run_length += current_block.length; + current_block = data_counter.NextWord(); + } + // Fill all valid values of this scan + std::memcpy(&output[num_valid_values], &src[idx_src], run_length * sizeof(T)); + num_valid_values += run_length; + idx_src += run_length; + valid_bits_offset += run_length; + // The current_block already computed, advance to next loop + continue; + } else if (!current_block.NoneSet()) { // Some values are null + arrow::internal::BitmapReader valid_bits_reader(valid_bits, valid_bits_offset, + current_block.length); + for (int64_t i = 0; i < current_block.length; i++) { + if (valid_bits_reader.IsSet()) { + output[num_valid_values] = src[idx_src]; + num_valid_values++; + } + idx_src++; + valid_bits_reader.Next(); + } + valid_bits_offset += current_block.length; + } else { // All null values + idx_src += current_block.length; + valid_bits_offset += current_block.length; + } + current_block = data_counter.NextWord(); + } + + return num_valid_values; +} + +/// \brief Expand the buffer but leave spaces for null entries. +/// +/// \param[in, out] buffer the in-place buffer +/// \param[in] num_values total size of buffer including null slots +/// \param[in] null_count number of null slots +/// \param[in] valid_bits bitmap data indicating position of valid slots +/// \param[in] valid_bits_offset offset into valid_bits +/// \return The number of values expanded, including nulls. +template <typename T> +inline int SpacedExpand(T* buffer, int num_values, int null_count, + const uint8_t* valid_bits, int64_t valid_bits_offset) { + constexpr uint64_t kBatchSize = 64; + static_assert(kBatchSize == 64, "Invalid batch size, BitBlockCounter stick to 64"); + constexpr uint64_t kBatchByteSize = kBatchSize / 8; + + // Point to end as we add the spacing from the back. + int idx_decode = num_values - null_count - 1; + int idx_buffer = num_values - 1; + int64_t idx_valid_bits = valid_bits_offset + idx_buffer; + + // Depending on the number of nulls, some of the value slots in buffer may + // be uninitialized, and this will cause valgrind warnings / potentially UB + std::memset(static_cast<void*>(&buffer[idx_decode + 1]), 0, null_count * sizeof(T)); Review comment: is this `static_cast` needed? ########## File path: cpp/src/arrow/util/spaced.h ########## @@ -0,0 +1,199 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. Review comment: I'm slightly ambivalent about having this code in a new header file, but it would make it easier to write unit tests for it, so I think it is OK ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
