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Merged
ChrisJChang merged 3 commits into from
Jun 22, 2026
Merged

Reduce startup time for gambit --help and gambit --version #590

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7caaf4a
Added fast track in core.cpp for arguments "--help", "-h" and "--vers…
anderkve May 5, 2026
df8abe7
Merge branch 'master' into improve_startup_time
anderkve May 6, 2026
469bb25
Preload lib: take care of --help / --version / no-args before main bi…
anderkve May 6, 2026
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65 changes: 65 additions & 0 deletions Core/include/gambit/Core/cli_help_text.hpp
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@@ -0,0 +1,65 @@
// GAMBIT: Global and Modular BSM Inference Tool
// *********************************************
/// \file
///
/// Top-level CLI usage text for the gambit executable.
///
/// Defined once here and consumed both by Gambit::gambit_core::bail()
/// in Core/src/core.cpp and by the preload library's
/// __attribute__((constructor)) in contrib/preload/gambit_preload.cpp,
/// which intercepts trivial flag-only invocations (--help, -h,
/// --version, no args) and exits before the main binary's C++ static
/// initialisers run.
///
/// *********************************************

#ifndef __gambit_cli_help_text_hpp__
#define __gambit_cli_help_text_hpp__

namespace Gambit
{

inline constexpr const char* cli_help_text =
"\nusage: gambit [options] [<command>] "
"\n "
"\nRun scan: "
"\n gambit -f <inifile> Start a scan using instructions from inifile "
"\n e.g.: gambit -f gambit.yaml "
"\n "
"\nAvailable commands: "
"\n modules List registered modules "
"\n backends List registered backends and their status "
"\n models List registered models and output model graph "
"\n capabilities List all registered function capabilities "
"\n scanners List registered scanners "
"\n test-functions List registered scanner test objective functions "
"\n <name> Give info on a specific module, module function, "
"\n backend, backend function, model, capability, "
"\n scanner or scanner test objective function "
"\n e.g.: gambit DarkBit "
"\n gambit GA_SimYieldTable_DarkSUSY "
"\n gambit Pythia "
"\n gambit get_abund_map_AlterBBN "
"\n gambit MSSM "
"\n gambit IC79WL_loglike "
"\n gambit MultiNest "
"\n "
"\nBasic options: "
"\n --version Display GAMBIT version information "
"\n -h/--help Display this usage information "
"\n -f <inifile> Start scan using <inifile> "
"\n -v/--verbose Turn on verbose mode "
"\n -d/--dryrun List the function evaluation order computed based "
"\n on inifile "
"\n -b/--backends List the backends required to fulfil dependencies "
"\n based on inifile "
"\n -r/--restart Restart the scan defined by <inifile>. Existing "
"\n output files for the run will be overwritten. "
"\n Default behaviour in the absence of this option is"
"\n to attempt to resume the scan from any existing "
"\n output. "
"\n\n\n";

}

#endif // defined __gambit_cli_help_text_hpp__
58 changes: 14 additions & 44 deletions Core/src/core.cpp
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Expand Up @@ -39,6 +39,7 @@

// Gambit headers
#include "gambit/Core/core.hpp"
#include "gambit/Core/cli_help_text.hpp"
#include "gambit/Core/error_handlers.hpp"
#include "gambit/Core/yaml_description_database.hpp"
#include "gambit/ScannerBit/plugin_loader.hpp"
Expand Down Expand Up @@ -81,50 +82,7 @@ namespace Gambit
void gambit_core::bail(int mpirank)
{
if (mpirank < 0) mpirank = GET_RANK;
if (mpirank == 0)
{
cout << "\nusage: gambit [options] [<command>] "
"\n "
"\nRun scan: "
"\n gambit -f <inifile> Start a scan using instructions from inifile "
"\n e.g.: gambit -f gambit.yaml "
"\n "
"\nAvailable commands: "
"\n modules List registered modules "
"\n backends List registered backends and their status "
"\n models List registered models and output model graph "
"\n capabilities List all registered function capabilities "
"\n scanners List registered scanners "
"\n test-functions List registered scanner test objective functions "
"\n <name> Give info on a specific module, module function, "
"\n backend, backend function, model, capability, "
"\n scanner or scanner test objective function "
"\n e.g.: gambit DarkBit "
"\n gambit GA_SimYieldTable_DarkSUSY "
"\n gambit Pythia "
"\n gambit get_abund_map_AlterBBN "
"\n gambit MSSM "
"\n gambit IC79WL_loglike "
"\n gambit MultiNest "
"\n "
"\nBasic options: "
"\n --version Display GAMBIT version information "
"\n -h/--help Display this usage information "
"\n -f <inifile> Start scan using <inifile> "
"\n -v/--verbose Turn on verbose mode "
"\n -d/--dryrun List the function evaluation order computed based "
"\n on inifile "
"\n -b/--backends List the backends required to fulfil dependencies "
"\n based on inifile "
"\n -r/--restart Restart the scan defined by <inifile>. Existing "
"\n output files for the run will be overwritten. "
"\n Default behaviour in the absence of this option is"
"\n to attempt to resume the scan from any existing "
"\n output. "
"\n"
<< endl
<< endl;
}
if (mpirank == 0) cout << cli_help_text; // from cli_help_text.hpp
logger().disable();
throw SilentShutdownException();
}
Expand Down Expand Up @@ -635,6 +593,18 @@ namespace Gambit
}
}

// Fast track for the options "--help", "-h", "--version" or no arguments
// at all. These all end in process_primary_options bailing out with usage
// or version text via SilentShutdownException, so we can skip the database
// build (check_databases) and the scanner-plugin enumeration done further down.
if (command == "--help" || command == "-h" || command == "--version" || command == "none")
{
if (not processed_options) (void) process_primary_options(argc, argv);
// process_primary_options is expected to bail() / throw for these
// inputs. If for some reason it returns, fall through to the existing
// logic below.
}

// Initial list of valid diagnostic commands
std::vector<str> valid_commands = initVector<str>("modules", "backends", "models", "capabilities", "scanners", "test-functions");

Expand Down
2 changes: 1 addition & 1 deletion cmake/contrib.cmake
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Expand Up @@ -70,7 +70,7 @@ endfunction()
set(name "gambit_preload")
set(dir "${CMAKE_BINARY_DIR}/contrib")
add_library(${name} SHARED "${PROJECT_SOURCE_DIR}/contrib/preload/gambit_preload.cpp")
target_include_directories(${name} PRIVATE "${PROJECT_SOURCE_DIR}/cmake/include" "${PROJECT_SOURCE_DIR}/Utils/include")
target_include_directories(${name} PRIVATE "${PROJECT_SOURCE_DIR}/cmake/include" "${PROJECT_SOURCE_DIR}/Core/include" "${PROJECT_SOURCE_DIR}/Utils/include")
set_target_properties(${name} PROPERTIES
ARCHIVE_OUTPUT_DIRECTORY "${dir}"
LIBRARY_OUTPUT_DIRECTORY "${dir}"
Expand Down
81 changes: 81 additions & 0 deletions contrib/preload/gambit_preload.cpp
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Expand Up @@ -17,6 +17,7 @@
/// \author Anders Kvellestad
/// anders.kvellestad@fys.uio.no
/// \date 2023 Oct
/// \date 2026 May
///
/// *********************************************

Expand All @@ -25,9 +26,60 @@
#include <cstring>

#include "gambit/cmake/cmake_variables.hpp"
#include "gambit/Core/cli_help_text.hpp"
#include "gambit/Utils/stringify.hpp"


// Classify the current gambit invocation by inspecting /proc/self/cmdline.
// Used by the constructor below to short-circuit trivial flag-only invocations
// (--help, -h, --version, no-args) before the main binary's C++ static
// initialisers run, saving several seconds of startup on e.g. `./gambit --help`.
//
// Detection is Linux-only (/proc/self/cmdline). On other systems this returns
// "normal" and the existing fast-paths in main()/run_diagnostic still cover
// the trivial invocations, just a bit slower.
typedef enum
{
GAMBIT_INVOCATION_NORMAL = 0,
GAMBIT_INVOCATION_HELP = 1, // --help, -h, or no arguments at all
GAMBIT_INVOCATION_VERSION = 2, // --version
} gambit_invocation_kind;

static gambit_invocation_kind gambit_classify_invocation()
{
#ifdef __linux__
FILE* f = fopen("/proc/self/cmdline", "r");
if (f == NULL) return GAMBIT_INVOCATION_NORMAL;
char buf[4096];
size_t n = fread(buf, 1, sizeof(buf) - 1, f);
fclose(f);
if (n == 0) return GAMBIT_INVOCATION_NORMAL;
buf[n] = '\0';
// Step past argv[0] (the executable path).
size_t i = 0;
while (i < n && buf[i] != '\0') ++i;
++i;
// No further arguments: print usage like `./gambit --help` does.
if (i >= n) return GAMBIT_INVOCATION_HELP;
// Walk argv looking for the first matching trivial flag, mirroring
// getopt's left-to-right parse order.
while (i < n)
{
const char* arg = &buf[i];
if (strcmp(arg, "--help") == 0 || strcmp(arg, "-h") == 0)
return GAMBIT_INVOCATION_HELP;
if (strcmp(arg, "--version") == 0)
return GAMBIT_INVOCATION_VERSION;
while (i < n && buf[i] != '\0') ++i;
++i;
}
return GAMBIT_INVOCATION_NORMAL;
#else
return GAMBIT_INVOCATION_NORMAL;
#endif
}


// Initializer; runs as soon as this library is loaded.
__attribute__((constructor))
static void initializer()
Expand All @@ -37,6 +89,35 @@ static void initializer()
if (strcmp(GAMBIT_VERSION_PATCH, "") != 0) printf("%s", "-" GAMBIT_VERSION_PATCH);
printf("\nhttp://gambitbsm.org\n\n\x1b[0m");

// Trivial flag-only invocations (--help, -h, --version, no-args)
// don't need anything else GAMBIT does at startup, so print the
// appropriate output and exit *here*, before the dynamic loader
// hands control to the executable's .init_array.
//
// The fast-paths in main() and run_diagnostic remain in place
// as a safety net for non-Linux systems where /proc/self/cmdline
// isn't available.
{
const gambit_invocation_kind kind = gambit_classify_invocation();
if (kind == GAMBIT_INVOCATION_HELP)
{
fputs(Gambit::cli_help_text, stdout);
exit(0);
}
if (kind == GAMBIT_INVOCATION_VERSION)
{
// The banner above is the version output; no further text needed.
exit(0);
}
if (kind == GAMBIT_INVOCATION_NORMAL)
{
// Normal GAMBIT invocation usually takes a few seconds of startup
// time, so let's inform the user that we are working on it.
printf("Initialising GAMBIT...\n");
}
}


// Set environment variable for RestFrames
#ifndef EXCLUDE_RESTFRAMES
{
Expand Down
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