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floating-point errors checker
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Interlibmath Portability with old g++ version Jul 26, 2019
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backend_mcaquad Begin of configuration of checkcancellation backend May 1, 2019
backend_verrou Possible to test easly a stronger random generator Jul 24, 2019
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.travis.yml Release v2.1.0 Nov 8, 2018
CHANGELOG.md Post-release v2.1.0 Nov 8, 2018
COPYING Added GPL headers Jun 13, 2016
Makefile.am Two scripts verrou_dd_line and verrou_dd_sym replace verrou_dd Jul 21, 2019
README.md Update documentation for v2.1.0 Nov 8, 2018
configure.ac env.sh export information about fma compilation status Aug 2, 2019
env.sh.in env.sh export information about fma compilation status Aug 2, 2019
generateBackendInterOperator.py Add an option to detect cancellation and correct the average mode of … May 1, 2019
interflop_backend_interface.h Integration (first step) of backend mcaquad from Verificarlo (commit … Mar 17, 2019
newbackend.md Add an option to detect cancellation and correct the average mode of … May 1, 2019
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valgrind.diff Update valgrind patch for 3.14.0 Nov 8, 2018
verrou.h ClientRequest with Partial Cover Feb 14, 2019
vr_clo.c Bug correction : --source works now with empty file Jul 17, 2019
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vr_error.c Add the --cc-gen-source to generate the list of cancellation May 12, 2019
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vr_generated_from_templates.h Add an option to detect cancellation and correct the average mode of … May 1, 2019
vr_include_trace.c The option --trace select the symbol in which the BB (BasicBloc) are … Feb 1, 2019
vr_instrumentOp_impl.h
vr_interp_operator_impl.h mcaquad Backend integration Mar 26, 2019
vr_interp_operator_template_2args.h mcaquad Backend integration Mar 26, 2019
vr_interp_operator_template_3args.h mcaquad Backend integration Mar 26, 2019
vr_interp_operator_template_cast.h
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vr_main.h Bug correction : --source works now with empty file Jul 17, 2019
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README.md

Verrou Build Status

Verrou helps you look for floating-point round-off errors in programs. It implements various forms of arithmetic, including:

  • all IEEE-754 standard rounding modes;

  • two variants of stochastic floating-point arithmetic based on random rounding: all floating-point operations are perturbed by randomly switching rounding modes. These can be seen as an asynchronous variant of the CESTAC method, or a subset of Monte Carlo Arithmetic, performing only output randomization through random rounding;

  • an emulation of single-precision rounding, in order to test the effect of reduced precision without any need to change the source code.

Verrou also comes with a verrou_dd utility, which simplifies the Verrou-based debugging process by implementing several variants of the Delta-Debugging algorithm. This allows easily locating which parts of the analyzed source code are likely to be responsible for Floating-Point-related instabilities.

The documentation for Verrou is available as a dedicated chapter in the Valgrind manual.

Installation

Get the sources

The preferred way to get Verrou sources is to download the latest stable version: v2.1.0. Older versions are available in the releases page. After downloading one of the released versions, skip to the "Configure and build" section below.

 

In order to build the development version of Verrou, it is necesary to first download a specific Valgrind version, and patch it. Fetch valgrind's sources:

git clone --branch=VALGRIND_3_14_0 --single-branch git://sourceware.org/git/valgrind.git valgrind-3.14.0+verrou-dev

Add verrou's sources to it:

cd valgrind
git clone --branch=master --single-branch https://github.com/edf-hpc/verrou.git verrou

patch -p1 <verrou/valgrind.diff

Configure and build

First, install all required dependencies (the names of relevant Debian packages are put in parentheses as examples):

  • C & C++ compilers (build-essential),
  • autoconf & automake (automake),
  • Python 3 (python3)
  • C standard library with debugging symbols (libc6-dbg).

 

Configure valgrind:

./autogen.sh
./configure --enable-only64bit --prefix=PREFIX

It is recommended to add the --enable-verrou-fma flag to the configuration above if your system supports FMA instructions. Depending on your system, it may be required to set CFLAGS so that it enables the use of FMA in your compiler:

./configure --enable-only64bit --enable-verrou-fma --prefix=PREFIX CFLAGS="-mfma"

 

Build and install:

make
make install

Load the environment

In order to actually use Verrou, you must load the correct environment. This can be done using:

source PREFIX/env.sh

Test (optional)

General tests

You can test the whole platform:

make check
perl tests/vg_regtest --all

or only verrou:

make -C tests check
make -C verrou check
perl tests/vg_regtest verrou

Specific tests

These tests are more closely related to the arithmetic part in Verrou:

make -C verrou/unitTest

Documentation

The documentation for verrou is available as a chapter in valgrind's manual.

 

You can also re-build it:

make -C docs html-docs man-pages

and browse it locally:

iceweasel docs/html/vr-manual.html

Beware, this requires lots of tools which are not necessarily tested for in configure, including (but not necessarily limited to):

  • xsltproc
  • docbook-xsl
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