Filament vectorization and avoiding OFT imports

.github/workflows/ci.yml

@@ -6,15 +6,34 @@ on:
   pull_request:
 
 jobs:
+  # Warms the OFT cache once. Without this every job below misses the same cache
+  # key at the same time and GitHub throttles the parallel 90 MB downloads.
+  setup-oft:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v5
+
+      - uses: astral-sh/setup-uv@v7
+
+      - name: Cache OFT
+        uses: actions/cache@v5
+        with:
+          path: submodules/OpenFUSIONToolkit
+          key: oft-v1.0.0-beta6-ubuntu-22.04
+
+      - name: Install
+        run: ./install.sh
+
   lint:
+    needs: setup-oft
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
 
       - name: Cache OFT
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: submodules/OpenFUSIONToolkit
           key: oft-v26.9-ubuntu-22.04
@@ -32,21 +51,26 @@ jobs:
         run: uv run isort synthwave/
 
   test:
+    needs: setup-oft
     runs-on: ubuntu-22.04
     strategy:
       matrix:
         test-file:
           - test_utils.py
           - test_equilibrium_field.py
           - test_filaments.py
+          - test_lazy_imports.py
+          - test_flux_matrix.py
+          - test_filament_discretization.py
+          - test_trace_regression.py
     name: test (${{ matrix.test-file }})
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
 
       - name: Cache OFT
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: submodules/OpenFUSIONToolkit
           key: oft-v26.9-ubuntu-22.04
@@ -58,15 +82,16 @@ jobs:
         run: uv run pytest synthwave/tests/${{ matrix.test-file }}
 
   test-thincurr-other:
+    needs: setup-oft
     runs-on: ubuntu-22.04
     name: test (test_thincurr.py - other)
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
 
       - name: Cache OFT
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: submodules/OpenFUSIONToolkit
           key: oft-v26.9-ubuntu-22.04
@@ -77,19 +102,24 @@ jobs:
       - name: Run tests
         run: uv run pytest synthwave/tests/test_thincurr.py --deselect synthwave/tests/test_thincurr.py::test_toroidal_angles
 
+      # Separate process: OFT_env can only be created once per process
+      - name: Run direct response tests
+        run: uv run pytest synthwave/tests/test_direct_response.py
+
   test-thincurr-toroidal-angles:
+    needs: setup-oft
     runs-on: ubuntu-22.04
     strategy:
       matrix:
         mode: ["m2n1", "m3n2", "m-3n2", "m3n1", "m4n3"]
     name: test (test_toroidal_angles[${{ matrix.mode }}])
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
 
       - name: Cache OFT
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: submodules/OpenFUSIONToolkit
           key: oft-v26.9-ubuntu-22.04
@@ -101,14 +131,15 @@ jobs:
         run: uv run pytest "synthwave/tests/test_thincurr.py::test_toroidal_angles[${{ matrix.mode }}]"
 
   notebooks:
+    needs: setup-oft
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
-      - uses: astral-sh/setup-uv@v5
+      - uses: astral-sh/setup-uv@v7
 
       - name: Cache OFT
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: submodules/OpenFUSIONToolkit
           key: oft-v26.9-ubuntu-22.04

install.sh

@@ -94,13 +94,25 @@ else
     TEMP_DIR=$(mktemp -d)
     trap "rm -rf $TEMP_DIR" EXIT
 
-    curl -L -o "$TEMP_DIR/$TARBALL" "$URL" || wget -O "$TEMP_DIR/$TARBALL" "$URL"
+    # -f makes HTTP errors a real failure instead of saving the error page as the
+    # tarball. Concurrent CI jobs can get throttled by GitHub, so retry with backoff.
+    curl -fL --retry 5 --retry-delay 5 --retry-all-errors \
+         -o "$TEMP_DIR/$TARBALL" "$URL" \
+        || wget --tries=5 --waitretry=5 -O "$TEMP_DIR/$TARBALL" "$URL" \
+        || error "Download failed: $URL"
+
+    # A throttled or redirected response can still land as a tiny file
+    DOWNLOAD_BYTES=$(stat -c %s "$TEMP_DIR/$TARBALL" 2>/dev/null || echo 0)
+    if [ "$DOWNLOAD_BYTES" -lt 1000000 ]; then
+        error "Download is only ${DOWNLOAD_BYTES} bytes, expected ~90 MB. GitHub likely rate-limited this request."
+    fi
 
     # Verify checksum if available
     if [ -n "${CHECKSUMS[$TARBALL]}" ]; then
         info "Verifying checksum..."
         if command -v sha256sum &>/dev/null; then
-            echo "${CHECKSUMS[$TARBALL]}  $TEMP_DIR/$TARBALL" | sha256sum -c - || error "Checksum verification failed!"
+            echo "${CHECKSUMS[$TARBALL]}  $TEMP_DIR/$TARBALL" | sha256sum -c - \
+                || error "Checksum mismatch for $TARBALL - the download is corrupt or the release asset changed."
             success "Checksum verified"
         else
             warn "sha256sum not available, skipping checksum verification"

synthwave/magnetic_geometry/equilibrium_field.py

@@ -14,10 +14,14 @@
 def biot_savart_cartesian(
     eval_point: np.ndarray, filament_points: np.ndarray, filament_current: float
 ):
-    """Biot-savart law in cartesian coordinates."""
-    r_prime = eval_point - filament_points
+    """Biot-savart law in cartesian coordinates.
+
+    Segment-midpoint rule, one current element per polyline segment.
+    """
+    dl = filament_points[1:] - filament_points[:-1]
+    midpoints = 0.5 * (filament_points[1:] + filament_points[:-1])
+    r_prime = eval_point - midpoints
     r_prime_norm = np.linalg.norm(r_prime, axis=1)
-    dl = np.gradient(filament_points, axis=0)
     dl_cross_r = np.cross(dl, r_prime)
     B_segments = (
         (mu_0 / (4 * np.pi))