diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index c6c6dc5..2531a8e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -3,8 +3,4 @@ stages:
 
 build:
   stage: build
-  script:
-  - mkdir build
-  - cd build
-  - cmake .. -DCMAKE_BUILD_TYPE=Debug
-  - make
+  script: ./ci/travis.sh
diff --git a/ci/get-nprocessors.sh b/ci/get-nprocessors.sh
new file mode 100644
index 0000000..43635e7
--- /dev/null
+++ b/ci/get-nprocessors.sh
@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# Copyright 2017 Google Inc.
+# All Rights Reserved.
+#
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# This file is typically sourced by another script.
+# if possible, ask for the precise number of processors,
+# otherwise take 2 processors as reasonable default; see
+# https://docs.travis-ci.com/user/speeding-up-the-build/#Makefile-optimization
+if [ -x /usr/bin/getconf ]; then
+    NPROCESSORS=$(/usr/bin/getconf _NPROCESSORS_ONLN)
+else
+    NPROCESSORS=2
+fi
+
+# as of 2017-09-04 Travis CI reports 32 processors, but GCC build
+# crashes if parallelized too much (maybe memory consumption problem),
+# so limit to 4 processors for the time being.
+if [ $NPROCESSORS -gt 4 ] ; then
+	echo "$0:Note: Limiting processors to use by make from $NPROCESSORS to 4."
+	NPROCESSORS=4
+fi
diff --git a/ci/travis.sh b/ci/travis.sh
new file mode 100644
index 0000000..948c4dc
--- /dev/null
+++ b/ci/travis.sh
@@ -0,0 +1,40 @@
+#!/usr/bin/env sh
+set -evx
+
+. ci/get-nprocessors.sh
+
+# if possible, ask for the precise number of processors,
+# otherwise take 2 processors as reasonable default; see
+# https://docs.travis-ci.com/user/speeding-up-the-build/#Makefile-optimization
+if [ -x /usr/bin/getconf ]; then
+    NPROCESSORS=$(/usr/bin/getconf _NPROCESSORS_ONLN)
+else
+    NPROCESSORS=2
+fi
+# as of 2017-09-04 Travis CI reports 32 processors, but GCC build
+# crashes if parallelized too much (maybe memory consumption problem),
+# so limit to 4 processors for the time being.
+if [ $NPROCESSORS -gt 4 ] ; then
+	echo "$0:Note: Limiting processors to use by make from $NPROCESSORS to 4."
+	NPROCESSORS=4
+fi
+# Tell make to use the processors. No preceding '-' required.
+MAKEFLAGS="j${NPROCESSORS}"
+export MAKEFLAGS
+
+env | sort
+
+# Set default values to OFF for these variables if not specified.
+: "${NO_EXCEPTION:=OFF}"
+: "${NO_RTTI:=OFF}"
+: "${COMPILER_IS_GNUCXX:=OFF}"
+
+mkdir build || true
+cd build
+export BUILD_TYPE=Debug
+
+cmake -DCMAKE_CXX_FLAGS=$CXX_FLAGS \
+      -DCMAKE_BUILD_TYPE=$BUILD_TYPE \
+      ..
+make
+CTEST_OUTPUT_ON_FAILURE=1 make test