Use absl's locale-independent conversion functions in XPRESS MPSolver interface

[flomnes]

Using such functions as std::stoi, std::stod, etc. caused us a lot of trouble because these functions are locale dependent, as illustrated below

#include <iostream>
#include <locale>
#include <string>

void convert(std::string locale)
{
    std::string value = "9.81";
    if (std::setlocale(LC_ALL, locale.c_str()))
    {
        double converted = std::stod(value);
        std::cout << "locale " << locale << " converted to " << converted << std::endl;
    }
    else
    {
        std::cout << "locale set failed for " << locale << std::endl;
    }
}
int main()
{
    convert("C");
    convert("fr_FR.utf8");
    // OUTPUT
    // locale C converted to 9.81
    // locale fr_FR.utf8 converted to 9
}

At first, we thought that using ScopedLocale would allow us to temporarily use the "C" locale, but this approach has multiple problems

1. It's not thread-safe. For example calling std::stod when the locale is being changed through std::setlocale is undefined behavior source.
2. C is hard, const char* pointers easily become dangling or invalid without the caller knowing

struct ScopedLocale {
  ScopedLocale() {
    oldLocale = std::setlocale(LC_NUMERIC, nullptr);
    auto newLocale = std::setlocale(LC_NUMERIC, "C");
    CHECK_EQ(std::string(newLocale), "C");
  }
  ~ScopedLocale() { std::setlocale(LC_NUMERIC, oldLocale); }

 private:
  const char* oldLocale;
};

We ran into an issue where the locale wasn't properly restored after using MPSolver::XpressInterface. So we decided to use absl's locale independent functions to perform that task.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[flomnes]

Hi @lperron it seems that this fix was neither shipped into v9.11 nor v9.12 since it was merged into google:main.

Do you plan to ship it in the next version ?

[lperron]

Can you check on the v99bugfix branch ? Laurent Perron | Operations Research | ***@***.*** | (33) 1 42 68 53 00 Le mar. 3 juin 2025, 14:01, Florian Omnès ***@***.***> a écrit :

…

*flomnes* left a comment (google/or-tools#4382) <#4382 (comment)> Hi @lperron <https://github.com/lperron> it seems that this fix was neither shipped into v9.11 nor v9.12 since it was merged into google:main. Do you plan to ship it in the next version ? — Reply to this email directly, view it on GitHub <#4382 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACUPL3LL4MD5NJVJT3J3RV33BWFBRAVCNFSM6AAAAAB6PSGVUCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDSMZUHEYTAMRYGI> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[flomnes]

Can you check on the v99bugfix branch ?

Unfortunately the ScopedLocale class is still defined & used in branch v99bugfix (commit 6275619).

[lperron]

And in main ? Sorry, I cannot check myself. Laurent Perron | Operations Research | ***@***.*** | (33) 1 42 68 53 00 Le mar. 3 juin 2025 à 16:00, Florian Omnès ***@***.***> a écrit :

…

*flomnes* left a comment (google/or-tools#4382) <#4382 (comment)> Can you check on the v99bugfix branch ? Unfortunately the ScopedLocale class is still defined & used in branch v99bugfix (commit 6275619 <6275619> ). — Reply to this email directly, view it on GitHub <#4382 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACUPL3I7YEP5SBAKNKSASED3BWS6FAVCNFSM6AAAAAB6PSGVUCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDSMZVGM4TONBVGM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[flomnes]

And in main ? Sorry, I cannot check myself.

Yes, oddly enough ScopedLocale can also be found in google:main (commit a90d9d9)

[lperron]

OK, we will re-apply the patch . Thanks for flagging. Laurent Perron | Operations Research | ***@***.*** | (33) 1 42 68 53 00 Le mar. 3 juin 2025 à 16:32, Florian Omnès ***@***.***> a écrit :

…

*flomnes* left a comment (google/or-tools#4382) <#4382 (comment)> And in main ? Sorry, I cannot check myself. Yes, oddly enough ScopedLocale can also be found in google:main (commit a90d9d9 <a90d9d9> ) — Reply to this email directly, view it on GitHub <#4382 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACUPL3JYSTQZOLFTT7SHDKD3BWWZVAVCNFSM6AAAAAB6PSGVUCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDSMZVGYYDCNZSGM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[flomnes]

OK, we will re-apply the patch . Thanks for flagging.

You're welcome !

[Mizux]

@flomnes can you check 1aad3b5
if OK I will cherry pick and apply it to main and v99bugfix branch of google/or-tools

note: I've used https://raw.githubusercontent.com/rte-france/or-tools/refs/heads/main/ortools/linear_solver/xpress_interface.cc as source of truth + clang-format --style=file -i ortools/linear_solver/xpress_interface.cc
aka see line 848 CHECK_STATUS() + void XpressInterface::Reset() rework

[flomnes]

@flomnes can you check 1aad3b5 if OK I will cherry pick and apply it to main and v99bugfix branch of google/or-tools

note: I've used https://raw.githubusercontent.com/rte-france/or-tools/refs/heads/main/ortools/linear_solver/xpress_interface.cc as source of truth + clang-format --style=file -i ortools/linear_solver/xpress_interface.cc aka see line 848 CHECK_STATUS() + void XpressInterface::Reset() rework

The proposed commit reverts the removal of XPRSloadlp's call in XpressInterface::Reset (see #4667), which we don't want. We only want to apply the removal of ScopedLocale (see #4382).

[Mizux]

@flomnes can you check 1aad3b5 if OK I will cherry pick and apply it to main and v99bugfix branch of google/or-tools
note: I've used https://raw.githubusercontent.com/rte-france/or-tools/refs/heads/main/ortools/linear_solver/xpress_interface.cc as source of truth + clang-format --style=file -i ortools/linear_solver/xpress_interface.cc aka see line 848 CHECK_STATUS() + void XpressInterface::Reset() rework

The proposed commit reverts the removal of XPRSloadlp's call in XpressInterface::Reset (see #4667), which we don't want. We only want to apply the removal of ScopedLocale (see #4382).

Granted ! Update the patch 573927e
If OK will be merged asap in main and v99bugfix...

[Mizux]

@flommes should we backport #4667 to v99bugfix branch aka our next release v9.13 + soon stable branch ?

[flomnes]

Granted ! Update the patch 573927e
If OK will be merged asap in main and v99bugfix...

573927e looks good, I approve this cherry-pick.

[flomnes]

@flommes should we backport #4667 to v99bugfix branch aka our next release v9.13 + soon stable branch ?

Yes, #4667 greatly improves performance for our use-cases so it would be nice to ship it in v9.13.

Thank you

[Mizux]

@flommes should we backport #4667 to v99bugfix branch aka our next release v9.13 + soon stable branch ?

Yes, #4667 greatly improves performance for our use-cases so it would be nice to ship it in v9.13.

Thank you

Cherry-pick done, hope to release this week !
ref: 6b83515