Mercurial > gemma
view pkg/controllers/cross.go @ 5520:05db984d3db1
Improve performance of bottleneck area calculation
Avoid buffer calculations by replacing them with simple distance comparisons
and calculate the boundary of the result geometry only once per iteration.
In some edge cases with very large numbers of iterations, this reduced
the runtime of a bottleneck import by a factor of more than twenty.
author | Tom Gottfried <tom@intevation.de> |
---|---|
date | Thu, 21 Oct 2021 19:50:39 +0200 |
parents | 5f47eeea988d |
children |
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// This is Free Software under GNU Affero General Public License v >= 3.0 // without warranty, see README.md and license for details. // // SPDX-License-Identifier: AGPL-3.0-or-later // License-Filename: LICENSES/AGPL-3.0.txt // // Copyright (C) 2018 by via donau // – Österreichische Wasserstraßen-Gesellschaft mbH // Software engineering by Intevation GmbH // // Author(s): // * Sascha L. Teichmann <sascha.teichmann@intevation.de> package controllers import ( "context" "database/sql" "fmt" "net/http" "time" "gemma.intevation.de/gemma/pkg/log" "gemma.intevation.de/gemma/pkg/mesh" "gemma.intevation.de/gemma/pkg/models" mw "gemma.intevation.de/gemma/pkg/middleware" ) func reproject( ctx context.Context, rp *models.Reprojector, src models.GeoJSONLineCoordinates, ) (models.GeoJSONLineCoordinates, error) { dst := make(models.GeoJSONLineCoordinates, len(src)) for i, s := range src { var err error if dst[i].Lat, dst[i].Lon, err = rp.Reproject( ctx, s.Lat, s.Lon, ); err != nil { return nil, err } } return dst, nil } const projectBackSQL = ` SELECT ST_AsBinary( ST_Transform(ST_GeomFromWKB($2, $1::integer), 4326))` func projectBack( ctx context.Context, line mesh.MultiLineStringZ, epsg uint32, conn *sql.Conn, ) (models.GeoJSONMultiLineCoordinatesZ, error) { var mls models.GeoJSONMultiLineCoordinatesZ err := conn.QueryRowContext( ctx, projectBackSQL, epsg, line.AsWKB(), ).Scan(&mls) return mls, err } func crossSection(req *http.Request) (jr mw.JSONResult, err error) { csi := mw.JSONInput(req).(*models.CrossSectionInput) start := time.Now() ctx := req.Context() conn := mw.JSONConn(req) tree, err := mesh.FromCache( ctx, conn, csi.Properties.Bottleneck, csi.Properties.Date.Time) log.Infof("loading mesh took %s\n", time.Since(start)) if err != nil { return } if tree == nil { err = mw.JSONError{ Code: http.StatusNotFound, Message: fmt.Sprintf("Cannot find survey for %s/%s.", csi.Properties.Bottleneck, csi.Properties.Date.Time), } return } // The coordinate system of the mesh is an UTM projection. // The input coordinates are in WGS84. // So we need to reproject them. start = time.Now() var rp *models.Reprojector if rp, err = models.NewReprojector( ctx, conn, models.WGS84, tree.EPSG(), ); err != nil { return } defer rp.Close() coords, err := reproject(ctx, rp, csi.Geometry.Coordinates) log.Infof("transforming input coords took %s\n", time.Since(start)) if err != nil { return } start = time.Now() var segments mesh.MultiLineStringZ for i := 0; i < len(coords)-1; i++ { c1 := &coords[i] c2 := &coords[i+1] verticalLine := mesh.NewVerticalLine(c1.Lat, c1.Lon, c2.Lat, c2.Lon) var line mesh.MultiLineStringZ tree.Vertical(c1.Lat, c1.Lon, c2.Lat, c2.Lon, func(t *mesh.Triangle) { if ls := verticalLine.Intersection(t); len(ls) > 0 { line = append(line, ls) } }) if len(line) > 0 { log.Infof("line length: %d\n", len(line)) // They are all on the segment (c1.Lat, c1.Lon) - (c2.Lat, c2.Lon). // Sort them by project them on this line. joined := line.JoinOnLine(c1.Lat, c1.Lon, c2.Lat, c2.Lon) log.Infof("joined length: %d\n", len(joined)) segments = append(segments, joined...) } } log.Infof("mesh traversal took %s\n", time.Since(start)) start = time.Now() var joined models.GeoJSONMultiLineCoordinatesZ joined, err = projectBack( ctx, segments, tree.EPSG(), conn, ) log.Infof("projecting back took %s\n", time.Since(start)) if err != nil { return } jr = mw.JSONResult{ Result: &models.CrossSectionOutput{ Type: "Feature", Geometry: models.CrossSectionOutputGeometry{ Type: "MultiLineString", Coordinates: joined, }, }, } return }