Improve support for gridSpec in encoder

.github/ci-config.yml

@@ -1,7 +1,9 @@
+dependency_cmake_options: |
+  ecmwf/eccodes: "-DENABLE_ECKIT_GEO=ON"
 dependencies: |
   ecmwf/ecbuild
   Deutsches-Klimarechenzentrum/libaec@refs/tags/v1.1.6
-  ecmwf/eccodes
   ecmwf/eckit
+  ecmwf/eccodes
 dependency_branch: develop
 parallelism_factor: 8

.github/ci-hpc-config.yml

@@ -3,8 +3,10 @@ build:
     - ninja
   dependencies:
     - ecmwf/ecbuild@develop
-    - ecmwf/eccodes@develop
     - ecmwf/eckit@develop
+    - ecmwf/eccodes@develop
+  dependency_cmake_options:
+    - "ecmwf/eccodes: '-DENABLE_ECKIT_GEO=ON'"
   parallel: 64
   env:
     - ECCODES_SAMPLES_PATH=$ECCODES_DIR/share/eccodes/samples

.github/workflows/pymetkit.yml

@@ -42,6 +42,23 @@ jobs:
         run: |
           mkdir stack-dependencies-build
           stack-dependencies-src/build.sh --build-path stack-dependencies-build --install-path dependencies  --with-deps libaec,pybind11
+      - name: Get eckit
+        uses: actions/checkout@v5
+        with:
+          repository: ecmwf/eckit
+          ref: develop
+          path: eckit-src
+      - name: Install eckit
+        run: |
+          mkdir eckit-build
+          cmake \
+            -B eckit-build \
+            -S eckit-src \
+            -GNinja \
+            -DCMAKE_INSTALL_PREFIX=dependencies \
+            -DCMAKE_PREFIX_PATH=dependencies \
+            -DCMAKE_BUILD_TYPE=RelWithDebInfo
+          cmake --build eckit-build -j -t install
       - name: Get eccodes
         uses: actions/checkout@v5
         with:
@@ -59,25 +76,9 @@ jobs:
             -DCMAKE_PREFIX_PATH=dependencies \
             -DCMAKE_BUILD_TYPE=RelWithDebInfo \
             -DENABLE_MEMFS=ON \
-            -DENABLE_AEC=ON
+            -DENABLE_AEC=ON \
+            -DENABLE_ECKIT_GEO=ON
           cmake --build eccodes-build -j -t install
-      - name: Get eckit
-        uses: actions/checkout@v5
-        with:
-          repository: ecmwf/eckit
-          ref: develop
-          path: eckit-src
-      - name: Install eckit
-        run: |
-          mkdir eckit-build
-          cmake \
-            -B eckit-build \
-            -S eckit-src \
-            -GNinja \
-            -DCMAKE_INSTALL_PREFIX=dependencies \
-            -DCMAKE_PREFIX_PATH=dependencies \
-            -DCMAKE_BUILD_TYPE=RelWithDebInfo
-          cmake --build eckit-build -j -t install
       - name: Archive with permissions preserved
         run: tar --zstd -cpf files.tar.zst dependencies/ ecbuild/
       - name: Upload dependencies

CMakeLists.txt

@@ -75,7 +75,7 @@ ecbuild_add_option( FEATURE ODB
 
 ecbuild_add_option( FEATURE GRIB2MARS
                     DEFAULT ON
-                    CONDITION HAVE_GRIB
+                    CONDITION HAVE_GRIB AND eckit_HAVE_ECKIT_GEO AND eccodes_HAVE_ECKIT_GEO
                     DESCRIPTION "Build the GRIB2MARS converter" )
 
 ecbuild_add_option( FEATURE MARS2MARS
@@ -84,7 +84,7 @@ ecbuild_add_option( FEATURE MARS2MARS
 
 ecbuild_add_option( FEATURE MARS2GRIB
                     DEFAULT ON
-                    CONDITION HAVE_GRIB AND eckit_HAVE_ECKIT_GEO
+                    CONDITION HAVE_GRIB AND eckit_HAVE_ECKIT_GEO AND eccodes_HAVE_ECKIT_GEO
                     DESCRIPTION "Build the MARS2GRIB encoder" )
 
 # Pythonic pybind11 interface (pymetkit)

src/metkit/grib2mars/api/Grib2Mars.cc

@@ -20,6 +20,8 @@
 
 #include "Grib2Mars.h"
 
+#include <cstdlib>
+
 #include "eckit/config/LocalConfiguration.h"
 #include "eckit/exception/Exceptions.h"
 #include "metkit/grib2mars/mappings/mappings.h"
@@ -38,18 +40,42 @@
 
 namespace metkit::grib2mars {
 
+namespace {
+
+/// @brief Apply environment side effects implied by a set of options.
+///
+/// When `skipSection3` is enabled the encoder delegates geometry handling to
+/// gridSpec/ecCodes, which requires ecCodes to be configured with eckit_geo
+/// support enabled. This is controlled by the `ECCODES_ECKIT_GEO` environment
+/// variable, so force it to "1" whenever `skipSection3` is requested.
+inline void applyOptionSideEffects(const Options& opts) {
+    if (opts.skipSection3) {
+        ::setenv("ECCODES_ECKIT_GEO", "1", 1);
+    }
+}
+
+}  // namespace
+
 // -----------------------------------------------------------------------------
 // Grib2Mars construction
 // -----------------------------------------------------------------------------
 
 /// @brief Default construct a Grib2Mars converter.
-Grib2Mars::Grib2Mars() : opts_{} {}
+Grib2Mars::Grib2Mars() : opts_{} {
+    applyOptionSideEffects(opts_);
+}
 
-Grib2Mars::Grib2Mars(const Options& opts) : opts_{opts} {}
+Grib2Mars::Grib2Mars(const Options& opts) : opts_{opts} {
+    applyOptionSideEffects(opts_);
+}
 
-Grib2Mars::Grib2Mars(const eckit::LocalConfiguration& opts) : opts_{detail::readOptions(opts)} {}
+Grib2Mars::Grib2Mars(const eckit::LocalConfiguration& opts) : opts_{detail::readOptions(opts)} {
+    applyOptionSideEffects(opts_);
+}
 
-Grib2Mars::Grib2Mars(OptionList opts) : opts_{detail::readOptions(opts)} {}
+Grib2Mars::Grib2Mars(OptionList opts) : opts_{detail::readOptions(opts)} {
+    applyOptionSideEffects(opts_);
+}
 
 /// @brief Convert an `eckit::LocalConfiguration` request.
 template <>

src/metkit/grib2mars/mappings/rules/grid.h

@@ -12,12 +12,27 @@ namespace metkit::grib2mars::rules::impl {
 template <class MarsDict, class MiscDict, class OptDict_t>
 void extractGrid(const std::string& keyword, const metkit::codes::CodesHandle& grib, MarsDict& mars, MiscDict& misc,
                  const OptDict_t& opts) {
+    using metkit::grib2mars::utils::dict_traits::get_or_throw;
     using metkit::grib2mars::utils::dict_traits::set_or_throw;
     using metkit::grib2mars::utils::exceptions::Grib2MarsGenericException;
 
     try {
-        (void)opts;
-        (void)misc;
+        if (get_or_throw<bool>(opts, "skipSection3")) {
+            if (!grib.has("gridSpec")) {
+                throw Grib2MarsGenericException("Missing GRIB key `gridSpec` required to extract MARS keyword `grid`",
+                                                Here());
+            }
+
+            const auto gridSpec = grib.getString("gridSpec");
+            set_or_throw<std::string>(mars, "grid", gridSpec);
+
+            if (grib.has("shapeOfTheEarth")) {
+                const long shapeOfTheEarth = grib.getLong("shapeOfTheEarth");
+                misc.set("shapeOfTheEarth", shapeOfTheEarth);
+            }
+
+            return;
+        }
 
         if (!grib.has("gridType")) {
             throw Grib2MarsGenericException(

src/metkit/grib2mars/mappings/rules/truncation.h

@@ -12,11 +12,50 @@ namespace metkit::grib2mars::rules::impl {
 template <class MarsDict, class MiscDict, class OptDict_t>
 void extractTruncation(const std::string& keyword, const metkit::codes::CodesHandle& grib, MarsDict& mars,
                        MiscDict& misc, const OptDict_t& opts) {
+    using metkit::grib2mars::utils::dict_traits::get_or_throw;
     using metkit::grib2mars::utils::dict_traits::set_or_throw;
     using metkit::grib2mars::utils::exceptions::Grib2MarsGenericException;
 
     try {
-        (void)opts;
+        if (get_or_throw<bool>(opts, "skipSection3")) {
+            if (!grib.has("gridSpec")) {
+                throw Grib2MarsGenericException("Missing GRIB key `gridSpec` required to extract MARS keyword `grid`",
+                                                Here());
+            }
+
+            const auto gridSpec = grib.getString("gridSpec");
+            set_or_throw<std::string>(mars, "grid", gridSpec);
+
+            const long j = grib.getLong("J");
+            const long k = grib.getLong("K");
+            const long m = grib.getLong("M");
+
+            if (j != k || j != m) {
+                throw Grib2MarsGenericException("Grib keys `J/K/M` must be equal! J=" + std::to_string(j) +
+                                                    ", K=" + std::to_string(k) + ", M=" + std::to_string(m),
+                                                Here());
+            }
+
+            if (grib.has("JS")) {
+                const long js = grib.getLong("JS");
+                const long ks = grib.getLong("KS");
+                const long ms = grib.getLong("MS");
+
+                if (js != ks || js != ms) {
+                    throw Grib2MarsGenericException("Grib keys `JS/KS/MS` must be equal! JS=" + std::to_string(js) +
+                                                        ", KS=" + std::to_string(ks) + ", MS=" + std::to_string(ms),
+                                                    Here());
+                }
+
+                if (js > 0 && js <= j) {
+                    // Set subSetTruncation based on JS, which is equal to KS and MS
+                    set_or_throw<long>(misc, "subSetTruncation", js);
+                }
+            }
+
+            return;
+        }
+
         if (!grib.has("gridType")) {
             throw Grib2MarsGenericException(
                 "Missing GRIB key `gridType` required to extract MARS keyword `" + keyword + "`", Here());

src/metkit/mars2grib/api/Mars2Grib.cc

@@ -60,6 +60,8 @@
 ///
 #include "Mars2Grib.h"
 
+#include <cstdlib>
+
 // other libraries
 #include "eckit/exception/Exceptions.h"
 
@@ -397,13 +399,37 @@ std::unique_ptr<metkit::codes::CodesHandle> Mars2Grib::finaliseEncoding(const Ca
 // Mars2Grib construction
 // -----------------------------------------------------------------------------
 
-Mars2Grib::Mars2Grib() : opts_{} {}
+namespace {
+
+/// @brief Apply environment side effects implied by a set of options.
+///
+/// When `skipSection3` is enabled the encoder delegates geometry handling to
+/// gridSpec/ecCodes, which requires ecCodes to be configured with eckit_geo
+/// support enabled. This is controlled by the `ECCODES_ECKIT_GEO` environment
+/// variable, so force it to "1" whenever `skipSection3` is requested.
+inline void applyOptionSideEffects(const Options& opts) {
+    if (opts.skipSection3) {
+        ::setenv("ECCODES_ECKIT_GEO", "1", 1);
+    }
+}
+
+}  // namespace
 
-Mars2Grib::Mars2Grib(const Options& opts) : opts_{opts} {}
+Mars2Grib::Mars2Grib() : opts_{} {
+    applyOptionSideEffects(opts_);
+}
 
-Mars2Grib::Mars2Grib(const eckit::LocalConfiguration& opts) : opts_{detail::readOptions(opts)} {}
+Mars2Grib::Mars2Grib(const Options& opts) : opts_{opts} {
+    applyOptionSideEffects(opts_);
+}
 
-Mars2Grib::Mars2Grib(OptionList opts) : opts_{detail::readOptions(opts)} {}
+Mars2Grib::Mars2Grib(const eckit::LocalConfiguration& opts) : opts_{detail::readOptions(opts)} {
+    applyOptionSideEffects(opts_);
+}
+
+Mars2Grib::Mars2Grib(OptionList opts) : opts_{detail::readOptions(opts)} {
+    applyOptionSideEffects(opts_);
+}
 
 
 // -----------------------------------------------------------------------------

src/metkit/mars2grib/backend/concepts/representation/representationEncoding.h

@@ -213,7 +213,7 @@ template <std::size_t Stage, std::size_t Section, RepresentationType Variant>
 constexpr bool representationApplicable() {
 
     // Disable the concept for the Dummy variant
-    if constexpr (Variant == RepresentationType::Dummy) {
+    if constexpr (Variant == RepresentationType::Dummy || Variant == RepresentationType::DummySH) {
         return false;
     }
 

src/metkit/mars2grib/backend/concepts/representation/representationEnum.h

@@ -93,7 +93,8 @@ enum class RepresentationType : std::size_t {
     Healpix,
     Orca,
     Fesom,
-    Dummy,  // Used to skip section3 resolution and delegate to gridSpec
+    Dummy,    // Used to skip section3 resolution and delegate to gridSpec
+    DummySH,  // Special case for spherical harmonics
     Default
 };
 
@@ -114,7 +115,7 @@ using RepresentationList =
     ValueList<RepresentationType::Latlon, RepresentationType::RegularGaussian, RepresentationType::ReducedGaussian,
               RepresentationType::SphericalHarmonics, RepresentationType::GeneralUnstructured,
               RepresentationType::Healpix, RepresentationType::Orca, RepresentationType::Fesom,
-              RepresentationType::Dummy, RepresentationType::Default>;
+              RepresentationType::Dummy, RepresentationType::DummySH, RepresentationType::Default>;
 
 
 ///
@@ -153,6 +154,7 @@ DEF(RepresentationType::Healpix, "healpix");
 DEF(RepresentationType::Orca, "orca");
 DEF(RepresentationType::Fesom, "fesom");
 DEF(RepresentationType::Dummy, "dummy");
+DEF(RepresentationType::DummySH, "dummySH");
 DEF(RepresentationType::Default, "default");
 
 #undef DEF

src/metkit/mars2grib/backend/concepts/representation/representationMatcher.h

@@ -67,6 +67,13 @@ std::size_t representationMatcher(const MarsDict_t& mars, const OptDict_t& opt)
 
         // This is used to fully delegate section3 setting to gridSpec
         if (get_or_throw<bool>(opt, "skipSection3")) {
+            const auto marsGrid = get_or_throw<std::string>(mars, "grid");
+            const auto gridType =
+                std::unique_ptr<const eckit::geo::Grid>(eckit::geo::GridFactory::make_from_string(marsGrid))->type();
+
+            if (gridType == "sh") {
+                return static_cast<std::size_t>(RepresentationType::DummySH);
+            }
             return static_cast<std::size_t>(RepresentationType::Dummy);
         }
 

src/metkit/mars2grib/backend/deductions/subSetTrunc.h

@@ -44,9 +44,10 @@
 
 // System includes
 #include <algorithm>
-#include <regex>
 #include <string>
 
+#include "eckit/geo/Grid.h"
+
 // Core deduction includes
 #include "metkit/config/LibMetkit.h"
 #include "metkit/mars2grib/utils/generalUtils.h"
@@ -92,8 +93,6 @@ long resolve_SubSetTruncation_or_throw(const MarsDict_t& mars, const ParDict_t&
     using metkit::mars2grib::utils::dict_traits::has;
     using metkit::mars2grib::utils::exceptions::Mars2GribDeductionException;
 
-    static const std::regex tGridRegex("^T(0|[1-9][0-9]*)$");
-
     try {
 
         // subSetTruncation must not be larger than any pentagonalResolutionParameter
@@ -102,13 +101,9 @@ long resolve_SubSetTruncation_or_throw(const MarsDict_t& mars, const ParDict_t&
 
         const long truncation = [&]() {
             if (get_or_throw<bool>(opt, "skipSection3")) {
-                const std::string grid = get_or_throw<std::string>(mars, "grid");
-                std::smatch tGridMatch;
-                if (!std::regex_match(grid, tGridMatch, tGridRegex) || tGridMatch.size() != 2) {
-                    throw Mars2GribDeductionException("Cannot extract truncation from MARS grid '" + grid + "'",
-                                                      Here());
-                }
-                return std::stol(tGridMatch[1].str());
+                const std::string grid           = get_or_throw<std::string>(mars, "grid");
+                const eckit::geo::Grid* gridSpec = eckit::geo::GridFactory::make_from_string(grid);
+                return static_cast<long>(gridSpec->truncation());
             }
             return get_or_throw<long>(mars, "truncation");
         }();