diff --git a/.circleci/config.yml b/.circleci/config.yml
deleted file mode 100644
index 98631a7..0000000
--- a/.circleci/config.yml
+++ /dev/null
@@ -1,220 +0,0 @@
-version: 2.1
-
-parameters:
-  nightly-version:
-    type: string
-    default: "nightly-2022-04-24"
-
-orbs:
-  codecov: codecov/codecov@1
-
-executors:
-  default:
-    docker:
-      - image: filecoin/rust:latest
-    working_directory: /mnt/crate
-    resource_class: 2xlarge
-  arm:
-    machine:
-      image: ubuntu-2004:202101-01
-    resource_class: arm.large
-
-restore-workspace: &restore-workspace
-  attach_workspace:
-    at: /mnt
-
-restore-cache: &restore-cache
-  restore_cache:
-    keys:
-      - cargo-v8-{{ checksum "Cargo.toml" }}-{{ checksum "Cargo.lock" }}-{{ arch }}
-      - repo-source-{{ .Branch }}-{{ .Revision }}
-
-jobs:
-  cargo_fetch:
-    executor: default
-    steps:
-      - checkout
-      - run:
-          name: Calculate dependencies
-          command: cargo generate-lockfile
-      - restore_cache:
-          keys:
-            - cargo-v8-{{ checksum "Cargo.toml" }}-{{ checksum "Cargo.lock" }}-{{ arch }}
-      - run: rm -rf ~/.rustup
-      - run: rustup self update
-      - run: rustup install stable
-      - run: rustup default stable
-      # A nightly build is needed for code coverage reporting and clippy
-      - run: rustup toolchain install << pipeline.parameters.nightly-version >>
-      - run: rustup component add --toolchain << pipeline.parameters.nightly-version >> llvm-tools-preview
-      - run: rustc --version
-      - run: rm -rf .git
-      - run: cargo update
-      - run: cargo fetch
-      - persist_to_workspace:
-          root: /mnt
-          paths:
-            - crate
-      - save_cache:
-          key: cargo-v8-{{ checksum "Cargo.toml" }}-{{ checksum "Cargo.lock" }}-{{ arch }}
-          paths:
-            - "~/.cargo"
-            - "~/.rustup"
-
-  rustfmt:
-    executor: default
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Run cargo fmt
-          command: cargo fmt --all -- --check
-
-  clippy:
-    executor: default
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Run cargo clippy
-          # Nightly is needed as `--all-targets` also runs on the benchmarks
-          command: cargo +<< pipeline.parameters.nightly-version >> clippy --all-targets --features gpu --workspace -- -D warnings
-      - run:
-         name: Run cargo clippy (benches)
-         command: cargo +<< pipeline.parameters.nightly-version >> clippy --all-targets --features gpu,__private_bench  --workspace -- -D warnings
-
-  build_default:
-    executor: default
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Run cargo build
-          command: cargo build --workspace
-
-  test_default:
-    executor: default
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Run cargo test
-          command: cargo test --workspace
-
-  test_portable:
-    executor: default
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Run cargo test
-          command: cargo test --features portable --workspace
-
-  test_arm:
-    executor: arm
-    steps:
-      - checkout
-      - run:
-          name: Install Rust
-          command: |
-            curl https://sh.rustup.rs -sSf | sh -s -- --profile minimal --default-toolchain $(cat rust-toolchain) -y
-      - run:
-          name: Run cargo test
-          command: cargo test --workspace
-      - run:
-          name: Run cargo test portable
-          command: cargo test --workspace --features portable
-
-  check_gpu:
-    executor: default
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Run cargo check
-          command: cargo check --features gpu --workspace
-
-  bench:
-    executor: default
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Run cargo bench
-          command: cargo +<< pipeline.parameters.nightly-version >> bench
-
-  coverage_run:
-    executor: default
-    environment:
-      # Incremental build is not supported when profiling
-      CARGO_INCREMENTAL: 0
-      # -Zinstrument-coverage: enable llvm coverage instrumentation
-      # -Ccodegen-units=1: building in parallel is not supported when profiling
-      # -Copt-level=0: disable optimizations for more accurate coverage
-      # -Clink-dead-code: dead code should be considered as not covered code
-      # -Coverflow-checks=off: checking for overflow is not needed for coverage reporting
-      # -Cinline-threshold=0: do not inline
-      RUSTFLAGS: -Zinstrument-coverage -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Cinline-threshold=0
-      # Make sure that each run of an executable creates a new profile file, with the default
-      # name they would override each other
-      LLVM_PROFILE_FILE: "%m.profraw"
-    steps:
-      - *restore-workspace
-      - *restore-cache
-      - run:
-          name: Set the PATH env variable
-          command: |
-            # Also put the Rust LLVM tools into the PATH.
-            echo 'export PATH="~/.rustup/toolchains/<< pipeline.parameters.nightly-version >>-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin:$PATH"' | tee --append $BASH_ENV
-            source $BASH_ENV
-      - run:
-          name: Generate coverage report
-          command: |
-            RUST_LOG=info cargo +<< pipeline.parameters.nightly-version >> test -- --nocapture
-
-            # Do *not* use sparse output. It leads to more lines that are not
-            # taken into account at all
-            llvm-profdata merge --output=default.profdata ./*.profraw
-
-            # The compiled files contain the coverage information. From running the tests we don't
-            # know what those files are called, hence use all files from the `./target/debug/deps`
-            # directory which don't have an extension.
-            OBJECT_FILES=$(find ./target/debug/deps/* -name '*' -not -name '*\.*' -printf '%p,'|head --bytes -1)
-            # Only export the coverage of this project, we don't care about coverage of
-            # dependencies
-            llvm-cov export --ignore-filename-regex=".cargo|.rustup" --format=lcov -instr-profile=default.profdata --object=${OBJECT_FILES} > lcov.info
-      # Codecov automatically merges the reports in case there are several ones uploaded
-      - codecov/upload:
-          file: lcov.info
-
-workflows:
-  version: 2.1
-
-  test:
-    jobs:
-      - cargo_fetch
-      - rustfmt:
-          requires:
-            - cargo_fetch
-      - clippy:
-          requires:
-            - cargo_fetch
-      - build_default:
-          requires:
-            - cargo_fetch
-      - bench:
-          requires:
-            - cargo_fetch
-      - test_default:
-          requires:
-            - cargo_fetch
-      - test_portable:
-          requires:
-            - cargo_fetch
-      - test_arm
-      - check_gpu:
-          requires:
-            - cargo_fetch
-      - coverage_run:
-          requires:
-            - cargo_fetch
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9e79af1..a3ea772 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -10,6 +10,7 @@ env:
   RUSTFLAGS: "-Dwarnings"
   CARGO_INCREMENTAL: 0
   RUST_BACKTRACE: 1
+  CARGO_REGISTRIES_CRATES_IO_PROTOCOL: sparse
 
 jobs:
   set-msrv:
@@ -17,44 +18,49 @@ jobs:
     outputs:
       msrv: ${{ steps.msrv.outputs.msrv }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - id: msrv
         run: echo "::set-output name=msrv::$(echo $MSRV)"
 
-  # NOTE vmx 2022-06-14: currently doesn't work, hence run it on CircleCI
-  # for now.
-  #linux_foreign:
-  #  strategy:
-  #    matrix:
-  #      include:
-  #        # 64-bit Linux/arm64
-  #        - target: aarch64-unknown-linux-gnu
-  #          rust: nightly
-  #          arch: aarch64
-  #
-  #  runs-on: ubuntu-18.04
-  #  steps:
-  #    - uses: actions/checkout@v2
-  #    - uses: uraimo/run-on-arch-action@v2.1.1
-  #      name: Run commands
-  #      id: runcmd
-  #      with:
-  #        arch: aarch64
-  #        distro: ubuntu18.04
-  #
-  #        # Not required, but speeds up builds by storing container images in
-  #        # a GitHub package registry.
-  #        githubToken: ${{ github.token }}
-  #
-  #        install: |
-  #          apt-get update -q -y
-  #          apt-get install -q -y ocl-icd-opencl-dev curl build-essential
-  #          curl https://sh.rustup.rs -sSf | sh -s -- --profile minimal --default-toolchain ${{ matrix.rust }} -y
-  #          source $HOME/.cargo/env
-  #
-  #        run: |
-  #          $HOME/.cargo/bin/cargo test --release --target ${{ matrix.target }}
-  #          $HOME/.cargo/bin/cargo test --release --features portable --target ${{ matrix.target }}
+  linux_foreign:
+    strategy:
+      matrix:
+        include:
+          # 64-bit Linux/arm64
+          - target: aarch64-unknown-linux-gnu
+            # NOTE vmx 2024-07-15: Use at least Rust 1.68.2 for now, so that we can use the sparse
+            # index. Without this, the build times out. Once the MSRV is >= 1.68.2, we don't need
+            # to special case anymore and can use the MSRV instead.
+            toolchain: 1.68.2
+            arch: aarch64
+
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: uraimo/run-on-arch-action@v2
+        name: Run tests
+        id: runtests
+        with:
+          arch: aarch64
+          distro: ubuntu22.04
+
+          # Not required, but speeds up builds by storing container images in
+          # a GitHub package registry.
+          githubToken: ${{ github.token }}
+
+          env: | # YAML, but pipe character is necessary
+            CARGO_REGISTRIES_CRATES_IO_PROTOCOL: sparse
+
+          install: |
+            apt-get update -q -y
+            apt-get install -q -y ocl-icd-opencl-dev curl build-essential
+            curl https://sh.rustup.rs -sSf | sh -s -- --profile minimal --default-toolchain ${{ matrix.toolchain }} -y
+            source $HOME/.cargo/env
+
+          run: |
+            $HOME/.cargo/bin/rustup override set ${{ matrix.toolchain }}
+            $HOME/.cargo/bin/cargo test --release --target ${{ matrix.target }}
+            $HOME/.cargo/bin/cargo test --release --features portable --target ${{ matrix.target }}
 
   # Linux tests
   linux:
@@ -64,32 +70,30 @@ jobs:
         include:
           # 32-bit Linux/x86
           - target: i686-unknown-linux-gnu
-            rust: ${{needs.set-msrv.outputs.msrv}}
+            toolchain: ${{needs.set-msrv.outputs.msrv}}
             deps: sudo apt update && sudo apt install gcc-multilib
           - target: i686-unknown-linux-gnu
-            rust: stable
+            toolchain: stable
             deps: sudo apt update && sudo apt install gcc-multilib
 
           # 64-bit Linux/x86_64
           - target: x86_64-unknown-linux-gnu
-            rust: ${{needs.set-msrv.outputs.msrv}}
+            toolchain: ${{needs.set-msrv.outputs.msrv}}
           - target: x86_64-unknown-linux-gnu
-            rust: stable
+            toolchain: stable
 
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
-          toolchain: ${{ matrix.rust }}
+          toolchain: ${{ matrix.toolchain }}
           target: ${{ matrix.target }}
-          override: true
       - name: Install opencl
         run: sudo apt-get install -y ocl-icd-opencl-dev
       - run: ${{ matrix.deps }}
-      - run: cargo test --target ${{ matrix.target }}
-      - run: cargo test --target ${{ matrix.target }} --features portable
+      - run: cargo +${{ matrix.toolchain }} test --target ${{ matrix.target }}
+      - run: cargo +${{ matrix.toolchain }} test --target ${{ matrix.target }} --features portable
 
   # macOS tests
   macos:
@@ -102,15 +106,13 @@ jobs:
 
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
           toolchain: ${{ matrix.toolchain }}
           target: x86_64-apple-darwin
-          override: true
-      - run: cargo test
-      - run: cargo test --features portable
+      - run: cargo +${{ matrix.toolchain }} test
+      - run: cargo +${{ matrix.toolchain }} test --features portable
 
  # Windows tests
   windows:
@@ -124,46 +126,54 @@ jobs:
 
     runs-on: windows-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
           toolchain: ${{ matrix.toolchain }}
           target: ${{ matrix.target }}
-          override: true
       - uses: msys2/setup-msys2@v2
-      - run: cargo test --target ${{ matrix.target }}
-      - run: cargo test --target ${{ matrix.target }} --features portable
+      - run: cargo +${{ matrix.toolchain }} test --target ${{ matrix.target }}
+      - run: cargo +${{ matrix.toolchain }} test --target ${{ matrix.target }} --features portable
 
   clippy_check:
+    needs: set-msrv
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@master
-      - run: rustup component add clippy
-      - uses: actions-rs/clippy-check@v1
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
         with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-          args: --all-features          
+            toolchain: ${{ needs.set-msrv.outputs.msrv }}
+            components: clippy
+      - name: Clippy
+        run: cargo clippy --all-features
 
   check_fmt_and_docs:
+    needs: set-msrv
     name: Checking fmt and docs
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
-
-    - uses: actions-rs/toolchain@v1
-      with:
-          profile: minimal
-          toolchain: nightly
-          override: true
-          components: rustfmt
-
-    - name: setup
-      run: |
-        rustup component add rustfmt
-        rustc --version
-    - name: fmt
-      run: cargo fmt --all -- --check
-
-    - name: Docs
-      run: cargo doc
+      - uses: actions/checkout@v4
+
+      - uses: dtolnay/rust-toolchain@master
+        with:
+            toolchain: ${{ needs.set-msrv.outputs.msrv }}
+            components: rustfmt
+
+      - name: setup
+        run: |
+          rustup component add rustfmt
+          rustc --version
+      - name: fmt
+        run: cargo fmt --all -- --check
+
+      - name: Docs
+        run: cargo doc
+
+  # Benchmarks need a nightly Rust
+  bench:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dtolnay/rust-toolchain@nightly
+      - name: Run cargo bench
+        run: cargo +nightly bench