From c1a15afec71eb0a8722ae52bd300d63a587c0561 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 11:30:32 +0200
Subject: [PATCH 01/28] CI Experimental [nogil] build of scikit-learn

---
 azure-pipelines.yml          | 33 +++++++++++++++++++++++++++++++++
 build_tools/azure/install.sh | 18 +++++++++++++++++-
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 2a44674ef8610..47523702fedc5 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -71,6 +71,39 @@ jobs:
         # Here we make sure, that they are still run on a regular basis.
         SKLEARN_SKIP_NETWORK_TESTS: '0'
 
+- template: build_tools/azure/posix.yml
+  # Experimental CPython branch without the Global Interpreter Lock:
+  # https://github.com/colesbury/nogil/
+  #
+  # The nogil build relies on a dedicated PyPI-style index to install patched
+  # versions of NumPy, SciPy and Cython maintained by @colesbury and that
+  # include specifc fixes to make them run correctly without relying on the GIL.
+  #
+  # The goal of this CI entry is to make sure that we do not introduce any
+  # dependency on the GIL in scikit-learn itself. An auxiliary goal is to early
+  # detect any regression in the patched build dependencies to report them
+  # upstream. The long-term goal is to be able to stop having to maintain
+  # multiprocessing based workaround / hacks in joblib / loky to make multi-CPU
+  # computing in scikit-learn efficient by default using regular threads.
+  #
+  # If this experimental entry becomes too unstable, feel free to disable it.
+  parameters:
+    name: Linux_nogil
+    vmImage: ubuntu-20.04
+    dependsOn: [git_commit, linting]
+    condition: |
+      and(
+        succeeded(),
+        not(contains(dependencies['git_commit']['outputs']['commit.message'], '[ci skip]')),
+        or(eq(variables['Build.Reason'], 'Schedule'),
+           contains(dependencies['git_commit']['outputs']['commit.message'], '[nogil]'
+          )
+        )
+      )
+    matrix:
+      pylatest_pip_scipy_dev:
+        DISTRIB: 'pip-nogil'
+
 # Check compilation with intel C++ compiler (ICC)
 - template: build_tools/azure/posix.yml
   parameters:
diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index ff89358c0c1f6..eec12f7268d18 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -56,6 +56,9 @@ pre_python_environment_install() {
         sudo apt-get update
         sudo apt-get install intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic
         source /opt/intel/oneapi/setvars.sh
+    elif [[ "$DISTRIB" == "pip-nogil" ]]; then
+        apt-get update
+        apt-get build-dep python3 python3-dev
     fi
 }
 
@@ -120,6 +123,19 @@ python_environment_install() {
         pip install https://github.com/joblib/joblib/archive/master.zip
         echo "Installing pillow master"
         pip install https://github.com/python-pillow/Pillow/archive/main.zip
+    elif [[ "$DISTRIB" == "pip-nogil" ]]; then
+        ORIGINAL_FOLDER=`pwd`
+        cd ..
+        git clone https://github.com/colesbury/nogil
+        cd nogil
+        ./configure && make -j 2
+        ./python.exe -m venv $VIRTUALENV
+        cd $ORIGINAL_FOLDER
+        source $VIRTUALENV/bin/activate
+
+        python -m pip install -U pip
+        echo "Installing build dependepencies with pip from the nogil repository"
+        pip install numpy scipy cython joblib threadpoolctl
     fi
 
     python -m pip install $(get_dep threadpoolctl $THREADPOOLCTL_VERSION) \
@@ -140,7 +156,6 @@ python_environment_install() {
 }
 
 scikit_learn_install() {
-    setup_ccache
     show_installed_libraries
 
     # Set parallelism to 3 to overlap IO bound tasks with CPU bound tasks on CI
@@ -183,6 +198,7 @@ scikit_learn_install() {
 
 main() {
     pre_python_environment_install
+    setup_ccache
     python_environment_install
     scikit_learn_install
 }

From b93f035a4f9d82dd3acf2df36bd6701be849e626 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 11:48:20 +0200
Subject: [PATCH 02/28] fix typos [nogil]

---
 azure-pipelines.yml          | 2 +-
 build_tools/azure/install.sh | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 47523702fedc5..350942b53eae6 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -101,7 +101,7 @@ jobs:
         )
       )
     matrix:
-      pylatest_pip_scipy_dev:
+      pylatest_pip_nogil:
         DISTRIB: 'pip-nogil'
 
 # Check compilation with intel C++ compiler (ICC)
diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index eec12f7268d18..780777871f040 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -57,8 +57,9 @@ pre_python_environment_install() {
         sudo apt-get install intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic
         source /opt/intel/oneapi/setvars.sh
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
-        apt-get update
-        apt-get build-dep python3 python3-dev
+        apt-get -yq update
+        apt-get install -yq ccache
+        apt-get build-dep -yq python3 python3-dev
     fi
 }
 

From 787b286d15fba44a6d7161350772303aa8ef97ac Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 11:57:40 +0200
Subject: [PATCH 03/28] Skip ccache setup if not installed [nogil]

---
 build_tools/azure/install.sh | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index 780777871f040..b2f692962c60c 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -20,14 +20,19 @@ make_conda() {
 }
 
 setup_ccache() {
-    echo "Setting up ccache with CCACHE_DIR=${CCACHE_DIR}"
-    mkdir /tmp/ccache/
-    which ccache
-    for name in gcc g++ cc c++ clang clang++ i686-linux-gnu-gcc i686-linux-gnu-c++ x86_64-linux-gnu-gcc x86_64-linux-gnu-c++ x86_64-apple-darwin13.4.0-clang x86_64-apple-darwin13.4.0-clang++; do
-      ln -s $(which ccache) "/tmp/ccache/${name}"
-    done
-    export PATH="/tmp/ccache/:${PATH}"
-    ccache -M 256M
+    CCACHE_BIN=`which ccache || echo ""`
+    if [[ "${CCACHE_BIN}" != "" ]]; then
+        echo "Setting up ccache with CCACHE_DIR=${CCACHE_DIR}"
+        mkdir /tmp/ccache/
+        which ccache
+        for name in gcc g++ cc c++ clang clang++ i686-linux-gnu-gcc i686-linux-gnu-c++ x86_64-linux-gnu-gcc x86_64-linux-gnu-c++ x86_64-apple-darwin13.4.0-clang x86_64-apple-darwin13.4.0-clang++; do
+        ln -s ${CCACHE_BIN} "/tmp/ccache/${name}"
+        done
+        export PATH="/tmp/ccache/:${PATH}"
+        ccache -M 256M
+    else
+        echo "ccache not found, skipping..."
+    fi
 }
 
 pre_python_environment_install() {

From 9ec5962a72559b53b2bb3fd25599f730b934f6a0 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 12:01:17 +0200
Subject: [PATCH 04/28] Move ccache setup back to itself original position
 [nogil]

---
 build_tools/azure/install.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index b2f692962c60c..8c63a353934e7 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -130,6 +130,7 @@ python_environment_install() {
         echo "Installing pillow master"
         pip install https://github.com/python-pillow/Pillow/archive/main.zip
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
+        setup_ccache  # speed-up the build of CPython it-self
         ORIGINAL_FOLDER=`pwd`
         cd ..
         git clone https://github.com/colesbury/nogil
@@ -162,6 +163,7 @@ python_environment_install() {
 }
 
 scikit_learn_install() {
+    setup_ccache
     show_installed_libraries
 
     # Set parallelism to 3 to overlap IO bound tasks with CPU bound tasks on CI
@@ -204,7 +206,6 @@ scikit_learn_install() {
 
 main() {
     pre_python_environment_install
-    setup_ccache
     python_environment_install
     scikit_learn_install
 }

From adcaf82483bf4f7b176e523364790cc7dfac4493 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 12:48:27 +0200
Subject: [PATCH 05/28] missing sudo [nogil]

---
 build_tools/azure/install.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index 8c63a353934e7..f1bfca4522aa0 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -62,9 +62,9 @@ pre_python_environment_install() {
         sudo apt-get install intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic
         source /opt/intel/oneapi/setvars.sh
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
-        apt-get -yq update
-        apt-get install -yq ccache
-        apt-get build-dep -yq python3 python3-dev
+        sudo apt-get -yq update
+        sudo apt-get install -yq ccache
+        sudo apt-get build-dep -yq python3 python3-dev
     fi
 }
 

From c64638c51d17765caf8492a88879eeb56e2fe235 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 13:07:03 +0200
Subject: [PATCH 06/28] Add the APT package sources [nogil]

---
 build_tools/azure/install.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index f1bfca4522aa0..9e138505184c9 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -62,6 +62,7 @@ pre_python_environment_install() {
         sudo apt-get install intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic
         source /opt/intel/oneapi/setvars.sh
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
+        echo "deb-src http://archive.ubuntu.com/ubuntu/ focal main" || sudo tee /etc/apt/sources.list
         sudo apt-get -yq update
         sudo apt-get install -yq ccache
         sudo apt-get build-dep -yq python3 python3-dev

From 64a09a72edd41e7b2df638b21871a604e0d4ede8 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 13:15:48 +0200
Subject: [PATCH 07/28] typo [nogil]

---
 build_tools/azure/install.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index 9e138505184c9..ee374a965623a 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -62,7 +62,7 @@ pre_python_environment_install() {
         sudo apt-get install intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic
         source /opt/intel/oneapi/setvars.sh
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
-        echo "deb-src http://archive.ubuntu.com/ubuntu/ focal main" || sudo tee /etc/apt/sources.list
+        echo "deb-src http://archive.ubuntu.com/ubuntu/ focal main" | sudo tee /etc/apt/sources.list
         sudo apt-get -yq update
         sudo apt-get install -yq ccache
         sudo apt-get build-dep -yq python3 python3-dev

From 16c7a245fccd570bb1a7c2a8fe9586598731d3e7 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 13:22:51 +0200
Subject: [PATCH 08/28] tee -a instead of tee [nogil]

---
 build_tools/azure/install.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index ee374a965623a..20dff87612338 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -62,7 +62,7 @@ pre_python_environment_install() {
         sudo apt-get install intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic
         source /opt/intel/oneapi/setvars.sh
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
-        echo "deb-src http://archive.ubuntu.com/ubuntu/ focal main" | sudo tee /etc/apt/sources.list
+        echo "deb-src http://archive.ubuntu.com/ubuntu/ focal main" | sudo tee -a /etc/apt/sources.list
         sudo apt-get -yq update
         sudo apt-get install -yq ccache
         sudo apt-get build-dep -yq python3 python3-dev

From 2966abaf8bdf8f47d175cc2f61f9755a1409c585 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 13:38:30 +0200
Subject: [PATCH 09/28] python.exe => python [nogil]

---
 build_tools/azure/install.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index 20dff87612338..dc1929dde9313 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -137,7 +137,7 @@ python_environment_install() {
         git clone https://github.com/colesbury/nogil
         cd nogil
         ./configure && make -j 2
-        ./python.exe -m venv $VIRTUALENV
+        ./python -m venv $VIRTUALENV
         cd $ORIGINAL_FOLDER
         source $VIRTUALENV/bin/activate
 

From 34b2a5bee418a4dcbeb962ab0900a7a9276808ba Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 13:52:39 +0200
Subject: [PATCH 10/28] VIRTUALENV is just a name, not a path [nogil]

---
 build_tools/azure/install.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index dc1929dde9313..a914cd1cb05ac 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -137,7 +137,7 @@ python_environment_install() {
         git clone https://github.com/colesbury/nogil
         cd nogil
         ./configure && make -j 2
-        ./python -m venv $VIRTUALENV
+        ./python -m venv $ORIGINAL_FOLDER/$VIRTUALENV
         cd $ORIGINAL_FOLDER
         source $VIRTUALENV/bin/activate
 

From e09e2efcd7e7e4b238acba67b4efd5a633e4e5f4 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 13:59:24 +0200
Subject: [PATCH 11/28] git clone --depth 1 [nogil]

---
 build_tools/azure/install.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index a914cd1cb05ac..3111cb71f8a55 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -134,7 +134,7 @@ python_environment_install() {
         setup_ccache  # speed-up the build of CPython it-self
         ORIGINAL_FOLDER=`pwd`
         cd ..
-        git clone https://github.com/colesbury/nogil
+        git clone --depth 1 https://github.com/colesbury/nogil
         cd nogil
         ./configure && make -j 2
         ./python -m venv $ORIGINAL_FOLDER/$VIRTUALENV

From d6f62189d813cd8acfdac2ad9c9b248ee14bd170 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 15:45:20 +0200
Subject: [PATCH 12/28] Make setup_ccache idempotent

---
 build_tools/azure/install.sh | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index 3111cb71f8a55..bff27e00ce7f3 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -8,6 +8,9 @@ source build_tools/shared.sh
 
 UNAMESTR=`uname`
 
+CCACHE_LINKS_DIR="/tmp/ccache"
+
+
 make_conda() {
     TO_INSTALL="$@"
     if [[ "$DISTRIB" == *"mamba"* ]]; then
@@ -21,14 +24,14 @@ make_conda() {
 
 setup_ccache() {
     CCACHE_BIN=`which ccache || echo ""`
-    if [[ "${CCACHE_BIN}" != "" ]]; then
+    if [[ "${CCACHE_BIN}" != "" ]] && [[ ! -d "${CCACHE_LINKS_DIR}" ]]; then
         echo "Setting up ccache with CCACHE_DIR=${CCACHE_DIR}"
-        mkdir /tmp/ccache/
+        mkdir ${CCACHE_LINKS_DIR}
         which ccache
         for name in gcc g++ cc c++ clang clang++ i686-linux-gnu-gcc i686-linux-gnu-c++ x86_64-linux-gnu-gcc x86_64-linux-gnu-c++ x86_64-apple-darwin13.4.0-clang x86_64-apple-darwin13.4.0-clang++; do
-        ln -s ${CCACHE_BIN} "/tmp/ccache/${name}"
+        ln -s ${CCACHE_BIN} "${CCACHE_LINKS_DIR}/${name}"
         done
-        export PATH="/tmp/ccache/:${PATH}"
+        export PATH="${CCACHE_LINKS_DIR}:${PATH}"
         ccache -M 256M
     else
         echo "ccache not found, skipping..."

From f5afcdc5fe6f4cb288b98a619c005ca3ad190c61 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 15:52:45 +0200
Subject: [PATCH 13/28] Better output messages in setup_ccache [nogil]

---
 build_tools/azure/install.sh | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index bff27e00ce7f3..c60ad4fcd6e6d 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -24,7 +24,11 @@ make_conda() {
 
 setup_ccache() {
     CCACHE_BIN=`which ccache || echo ""`
-    if [[ "${CCACHE_BIN}" != "" ]] && [[ ! -d "${CCACHE_LINKS_DIR}" ]]; then
+    if [[ "${CCACHE_BIN}" == "" ]]; then
+        echo "ccache not found, skipping..."
+    elif [[ -d "${CCACHE_LINKS_DIR}" ]]; then
+        echo "ccache already configured, skipping..."
+    else
         echo "Setting up ccache with CCACHE_DIR=${CCACHE_DIR}"
         mkdir ${CCACHE_LINKS_DIR}
         which ccache
@@ -33,8 +37,6 @@ setup_ccache() {
         done
         export PATH="${CCACHE_LINKS_DIR}:${PATH}"
         ccache -M 256M
-    else
-        echo "ccache not found, skipping..."
     fi
 }
 

From f94cfb84724e9def59f43893a8398e84b6ab328c Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 16:42:32 +0200
Subject: [PATCH 14/28] activate venv in tests [nogil]

---
 build_tools/azure/test_script.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/test_script.sh b/build_tools/azure/test_script.sh
index 46f6dc7d43943..152ad8a9f5743 100755
--- a/build_tools/azure/test_script.sh
+++ b/build_tools/azure/test_script.sh
@@ -7,7 +7,7 @@ source build_tools/shared.sh
 
 if [[ "$DISTRIB" =~ ^conda.* ]]; then
     source activate $VIRTUALENV
-elif [[ "$DISTRIB" == "ubuntu" ]] || [[ "$DISTRIB" == "debian-32" ]]; then
+elif [[ "$DISTRIB" == "ubuntu" ]] || [[ "$DISTRIB" == "debian-32" ]] || [[ "$DISTRIB" == "pip-nogil" ]]; then
     source $VIRTUALENV/bin/activate
 fi
 

From 17967d766c8cc8ce7660e3a3f3895a3916374ebd Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 21 Apr 2022 19:49:22 +0200
Subject: [PATCH 15/28] Try to disable xdist [nogil]

Co-authored-by: Thomas J. Fan <thomasjpfan@gmail.com>
---
 azure-pipelines.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 350942b53eae6..f428f47be410d 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -103,6 +103,7 @@ jobs:
     matrix:
       pylatest_pip_nogil:
         DISTRIB: 'pip-nogil'
+        PYTEST_XDIST_VERSION: 'none'
 
 # Check compilation with intel C++ compiler (ICC)
 - template: build_tools/azure/posix.yml

From 4aa94677de4eb5fba65262a3238e3f4bcc81ae46 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Wed, 27 Apr 2022 11:46:17 +0200
Subject: [PATCH 16/28] Trigger [nogil] build


From 715546dea61d7ced0691f3a6486685dc262c5bbe Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Wed, 27 Apr 2022 14:32:44 +0200
Subject: [PATCH 17/28] enable nogil venv for doctests

---
 build_tools/azure/test_docs.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/test_docs.sh b/build_tools/azure/test_docs.sh
index 18b3ccb148b5e..ac9002747c50e 100755
--- a/build_tools/azure/test_docs.sh
+++ b/build_tools/azure/test_docs.sh
@@ -4,7 +4,7 @@ set -e
 
 if [[ "$DISTRIB" =~ ^conda.* ]]; then
     source activate $VIRTUALENV
-elif [[ "$DISTRIB" == "ubuntu" ]]; then
+elif [[ "$DISTRIB" == "ubuntu" ]] || [[ "$DISTRIB" == "pip-nogil"; then
     source $VIRTUALENV/bin/activate
 fi
 

From 3a9ebd244dbed320070fa207f28ca66437293168 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Wed, 27 Apr 2022 14:33:26 +0200
Subject: [PATCH 18/28] Trigger [nogil]


From 7767753eab74293e3dd4f38b6e093d455ad00ca8 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Wed, 27 Apr 2022 14:47:28 +0200
Subject: [PATCH 19/28] Fixed a typo [nogil]

---
 build_tools/azure/test_docs.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/test_docs.sh b/build_tools/azure/test_docs.sh
index ac9002747c50e..d40d2c55eae32 100755
--- a/build_tools/azure/test_docs.sh
+++ b/build_tools/azure/test_docs.sh
@@ -4,7 +4,7 @@ set -e
 
 if [[ "$DISTRIB" =~ ^conda.* ]]; then
     source activate $VIRTUALENV
-elif [[ "$DISTRIB" == "ubuntu" ]] || [[ "$DISTRIB" == "pip-nogil"; then
+elif [[ "$DISTRIB" == "ubuntu" ]] || [[ "$DISTRIB" == "pip-nogil" ]]; then
     source $VIRTUALENV/bin/activate
 fi
 

From 8173b1cc0cb04ee26fa358187d44727b73a3aaea Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 28 Apr 2022 11:33:13 +0200
Subject: [PATCH 20/28] disable coverage for [nogil]

---
 azure-pipelines.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index f428f47be410d..0292b966f4465 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -104,6 +104,7 @@ jobs:
       pylatest_pip_nogil:
         DISTRIB: 'pip-nogil'
         PYTEST_XDIST_VERSION: 'none'
+        COVERAGE: 'false'
 
 # Check compilation with intel C++ compiler (ICC)
 - template: build_tools/azure/posix.yml

From baa4d4cb73846b35527412504c79e67bb6427a95 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Thu, 28 Apr 2022 11:58:40 +0200
Subject: [PATCH 21/28] Re-enable pytext-xdist for [nogil]

---
 azure-pipelines.yml | 1 -
 1 file changed, 1 deletion(-)

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 0292b966f4465..020d007acc651 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -103,7 +103,6 @@ jobs:
     matrix:
       pylatest_pip_nogil:
         DISTRIB: 'pip-nogil'
-        PYTEST_XDIST_VERSION: 'none'
         COVERAGE: 'false'
 
 # Check compilation with intel C++ compiler (ICC)

From c872deaa7b4e60651ea005af06b291a2a0a30135 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Fri, 29 Apr 2022 09:52:33 +0200
Subject: [PATCH 22/28] Document the [nogil] commit flag

---
 doc/developers/contributing.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/developers/contributing.rst b/doc/developers/contributing.rst
index 445a9d2211733..a8ab323daefb3 100644
--- a/doc/developers/contributing.rst
+++ b/doc/developers/contributing.rst
@@ -552,6 +552,7 @@ message, the following actions are taken.
     [cd build gh]          CD is run only for GitHub Actions
     [lint skip]            Azure pipeline skips linting
     [scipy-dev]            Build & test with our dependencies (numpy, scipy, etc ...) development builds
+    [nogil]                Build & test with the nogil experimental branches of CPython, Cython, NumPy, SciPy...
     [icc-build]            Build & test with the Intel C compiler (ICC)
     [pypy]                 Build & test with PyPy
     [doc skip]             Docs are not built

From b7a84e98a34b2a476b6ec5ca6819a76d10c2a4fe Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Fri, 29 Apr 2022 09:53:21 +0200
Subject: [PATCH 23/28] Apply suggestions from code review [nogil]

Co-authored-by: Thomas J. Fan <thomasjpfan@gmail.com>
---
 build_tools/azure/test_docs.sh   | 2 +-
 build_tools/azure/test_script.sh | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/build_tools/azure/test_docs.sh b/build_tools/azure/test_docs.sh
index d40d2c55eae32..1d28f64a036cd 100755
--- a/build_tools/azure/test_docs.sh
+++ b/build_tools/azure/test_docs.sh
@@ -4,7 +4,7 @@ set -e
 
 if [[ "$DISTRIB" =~ ^conda.* ]]; then
     source activate $VIRTUALENV
-elif [[ "$DISTRIB" == "ubuntu" ]] || [[ "$DISTRIB" == "pip-nogil" ]]; then
+elif [[ "$DISTRIB" == "ubuntu" || "$DISTRIB" == "pip-nogil" ]]; then
     source $VIRTUALENV/bin/activate
 fi
 
diff --git a/build_tools/azure/test_script.sh b/build_tools/azure/test_script.sh
index 4f99a1fc3c9a5..3d74a0d98b374 100755
--- a/build_tools/azure/test_script.sh
+++ b/build_tools/azure/test_script.sh
@@ -7,7 +7,7 @@ source build_tools/shared.sh
 
 if [[ "$DISTRIB" =~ ^conda.* ]]; then
     source activate $VIRTUALENV
-elif [[ "$DISTRIB" == "ubuntu" ]] || [[ "$DISTRIB" == "debian-32" ]] || [[ "$DISTRIB" == "pip-nogil" ]]; then
+elif [[ "$DISTRIB" == "ubuntu" || "$DISTRIB" == "debian-32" || "$DISTRIB" == "pip-nogil" ]]; then
     source $VIRTUALENV/bin/activate
 fi
 

From bb79bb425b1df9f6f025394be5aecaaeba7d8eaf Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Fri, 29 Apr 2022 09:57:46 +0200
Subject: [PATCH 24/28] More explicit comment on the [nogil] specific index

---
 build_tools/azure/install.sh | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index c60ad4fcd6e6d..8404c036b665f 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -147,7 +147,11 @@ python_environment_install() {
         source $VIRTUALENV/bin/activate
 
         python -m pip install -U pip
-        echo "Installing build dependepencies with pip from the nogil repository"
+        # The pip version that comes with the nogil branch of CPython
+        # automatically uses the custom nogil index as its highest priority
+        # index to fetch patched versions of libraries with native code that
+        # would otherwise depend on the GIL.
+        echo "Installing build dependepencies with pip from the nogil repository: https://d1yxz45j0ypngg.cloudfront.net/"
         pip install numpy scipy cython joblib threadpoolctl
     fi
 

From 465a18316a47e90747cee9fc9a054e5da80e8a4d Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Fri, 29 Apr 2022 10:41:25 +0200
Subject: [PATCH 25/28] Typo [ci skip]

---
 build_tools/azure/install.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index 8404c036b665f..ac160105ab085 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -151,7 +151,7 @@ python_environment_install() {
         # automatically uses the custom nogil index as its highest priority
         # index to fetch patched versions of libraries with native code that
         # would otherwise depend on the GIL.
-        echo "Installing build dependepencies with pip from the nogil repository: https://d1yxz45j0ypngg.cloudfront.net/"
+        echo "Installing build dependencies with pip from the nogil repository: https://d1yxz45j0ypngg.cloudfront.net/"
         pip install numpy scipy cython joblib threadpoolctl
     fi
 

From 6729e0b4b695f03d75ad6333d262aaa1bc240ca3 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Fri, 29 Apr 2022 10:45:22 +0200
Subject: [PATCH 26/28] Trigger [nogil]


From 4b478ad72e90779d52cefbd0923c7979ec3d3f95 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Mon, 2 May 2022 12:19:37 +0200
Subject: [PATCH 27/28] reorg install script for [nogil]

---
 build_tools/azure/install.sh | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index ac160105ab085..244a61defc37a 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -124,17 +124,6 @@ python_environment_install() {
         # do not install dependencies for lightgbm since it requires scikit-learn.
         python -m pip install "lightgbm>=3.0.0" --no-deps
 
-    elif [[ "$DISTRIB" == "conda-pip-scipy-dev" ]]; then
-        make_conda "ccache python=$PYTHON_VERSION"
-        python -m pip install -U pip
-        echo "Installing numpy and scipy master wheels"
-        dev_anaconda_url=https://pypi.anaconda.org/scipy-wheels-nightly/simple
-        pip install --pre --upgrade --timeout=60 --extra-index $dev_anaconda_url numpy pandas scipy
-        pip install --pre cython
-        echo "Installing joblib master"
-        pip install https://github.com/joblib/joblib/archive/master.zip
-        echo "Installing pillow master"
-        pip install https://github.com/python-pillow/Pillow/archive/main.zip
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
         setup_ccache  # speed-up the build of CPython it-self
         ORIGINAL_FOLDER=`pwd`
@@ -153,6 +142,19 @@ python_environment_install() {
         # would otherwise depend on the GIL.
         echo "Installing build dependencies with pip from the nogil repository: https://d1yxz45j0ypngg.cloudfront.net/"
         pip install numpy scipy cython joblib threadpoolctl
+
+    elif [[ "$DISTRIB" == "conda-pip-scipy-dev" ]]; then
+        make_conda "ccache python=$PYTHON_VERSION"
+        python -m pip install -U pip
+        echo "Installing numpy and scipy master wheels"
+        dev_anaconda_url=https://pypi.anaconda.org/scipy-wheels-nightly/simple
+        pip install --pre --upgrade --timeout=60 --extra-index $dev_anaconda_url numpy pandas scipy
+        pip install --pre cython
+        echo "Installing joblib master"
+        pip install https://github.com/joblib/joblib/archive/master.zip
+        echo "Installing pillow master"
+        pip install https://github.com/python-pillow/Pillow/archive/main.zip
+
     fi
 
     python -m pip install $(get_dep threadpoolctl $THREADPOOLCTL_VERSION) \

From 3598eb67d9d1b502bdc3273768a00316e10c3432 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Mon, 2 May 2022 12:21:34 +0200
Subject: [PATCH 28/28] reorg install script for [nogil]

---
 build_tools/azure/install.sh | 36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/build_tools/azure/install.sh b/build_tools/azure/install.sh
index 244a61defc37a..cfc563a4f9f65 100755
--- a/build_tools/azure/install.sh
+++ b/build_tools/azure/install.sh
@@ -58,6 +58,12 @@ pre_python_environment_install() {
         apt-get -yq update
         apt-get -yq install build-essential
 
+    elif [[ "$DISTRIB" == "pip-nogil" ]]; then
+        echo "deb-src http://archive.ubuntu.com/ubuntu/ focal main" | sudo tee -a /etc/apt/sources.list
+        sudo apt-get -yq update
+        sudo apt-get install -yq ccache
+        sudo apt-get build-dep -yq python3 python3-dev
+
     elif [[ "$BUILD_WITH_ICC" == "true" ]]; then
         wget https://apt.repos.intel.com/intel-gpg-keys/GPG-PUB-KEY-INTEL-SW-PRODUCTS.PUB
         sudo apt-key add GPG-PUB-KEY-INTEL-SW-PRODUCTS.PUB
@@ -66,11 +72,7 @@ pre_python_environment_install() {
         sudo apt-get update
         sudo apt-get install intel-oneapi-compiler-dpcpp-cpp-and-cpp-classic
         source /opt/intel/oneapi/setvars.sh
-    elif [[ "$DISTRIB" == "pip-nogil" ]]; then
-        echo "deb-src http://archive.ubuntu.com/ubuntu/ focal main" | sudo tee -a /etc/apt/sources.list
-        sudo apt-get -yq update
-        sudo apt-get install -yq ccache
-        sudo apt-get build-dep -yq python3 python3-dev
+
     fi
 }
 
@@ -124,6 +126,18 @@ python_environment_install() {
         # do not install dependencies for lightgbm since it requires scikit-learn.
         python -m pip install "lightgbm>=3.0.0" --no-deps
 
+    elif [[ "$DISTRIB" == "conda-pip-scipy-dev" ]]; then
+        make_conda "ccache python=$PYTHON_VERSION"
+        python -m pip install -U pip
+        echo "Installing numpy and scipy master wheels"
+        dev_anaconda_url=https://pypi.anaconda.org/scipy-wheels-nightly/simple
+        pip install --pre --upgrade --timeout=60 --extra-index $dev_anaconda_url numpy pandas scipy
+        pip install --pre cython
+        echo "Installing joblib master"
+        pip install https://github.com/joblib/joblib/archive/master.zip
+        echo "Installing pillow master"
+        pip install https://github.com/python-pillow/Pillow/archive/main.zip
+
     elif [[ "$DISTRIB" == "pip-nogil" ]]; then
         setup_ccache  # speed-up the build of CPython it-self
         ORIGINAL_FOLDER=`pwd`
@@ -143,18 +157,6 @@ python_environment_install() {
         echo "Installing build dependencies with pip from the nogil repository: https://d1yxz45j0ypngg.cloudfront.net/"
         pip install numpy scipy cython joblib threadpoolctl
 
-    elif [[ "$DISTRIB" == "conda-pip-scipy-dev" ]]; then
-        make_conda "ccache python=$PYTHON_VERSION"
-        python -m pip install -U pip
-        echo "Installing numpy and scipy master wheels"
-        dev_anaconda_url=https://pypi.anaconda.org/scipy-wheels-nightly/simple
-        pip install --pre --upgrade --timeout=60 --extra-index $dev_anaconda_url numpy pandas scipy
-        pip install --pre cython
-        echo "Installing joblib master"
-        pip install https://github.com/joblib/joblib/archive/master.zip
-        echo "Installing pillow master"
-        pip install https://github.com/python-pillow/Pillow/archive/main.zip
-
     fi
 
     python -m pip install $(get_dep threadpoolctl $THREADPOOLCTL_VERSION) \