Engine I/O and run modes
Run modes of the OpenMP SWAT+ fork (OMP_NUM_THREADS, SWATPLUS_ROUTING_SERIAL), print_filter.prt channel filtering, and NetCDF-4 output (cdfout = y).
Run modes
Downloaded models run with any compatible SWAT+ binary. The SWATGenX OpenMP fork adds shared-memory parallelism and optional NetCDF-4 output; hydrologic equations are unchanged. Build the fork with the Compile the SWAT+ fork chapter rather than improvising compiler flags.
# 1. serial reference OMP_NUM_THREADS=1 ./swatplus # 2. HRU-parallel (routing in command order) OMP_NUM_THREADS=8 SWATPLUS_ROUTING_SERIAL=1 ./swatplus # 3. full routing wavefront (fastest) OMP_NUM_THREADS=8 SWATPLUS_ROUTING_SERIAL=0 ./swatplus
- Optional NetCDF: set cdfout = y under the csvout/dbout/cdfout line in
print.prt; SWATPLUS_NC_DEFLATE controls compression (default 4). - Correctness check for a given build: run the same model at 1 and N threads on that binary and compare outputs for the streams you care about.
- Scoped identity: production/canary verification compares the same certified build under controlled conditions — do not generalize an unqualified “identical at every thread count on every machine” claim from this page.
- mgt_out.txt caveat: when management text output is enabled, line order can differ across parallel runs even when sorted content matches; NetCDF mode (cdfout = y) also suppresses that text stream.
print_filter.prt
Optional file in the run directory (fixed name print_filter.prt). Absent file → all channels are written, exactly as stock SWAT+. It filters only the channel_sd_{day,mon,yr,aa} streams — no other object is affected.
print_filter.prt: limit channel_sd output to listed channel units (1-based). # Present in shipped packages when gauges are assigned channel_sd 12 45
| Rule | Behavior |
|---|---|
| Blank lines / # lines | Skipped (comments allowed anywhere) |
| Line whose first token contains "channel_sd" | Starts the channel list section |
| Lines inside the section | Each must parse as one integer channel unit (1-based chandeg index); the first non-integer line ends the section |
| Range syntax (e.g. 12-45) | Not supported — one id per line |
| Valid ids | 1 ≤ id ≤ number of chandeg channels; out-of-range ids ignored |
| Keyword present, zero valid ids | Filter active with an empty list — no channel_sd files are opened at all |
| File absent or no channel_sd keyword | No filtering; all channels written |
SWATGenX-shipped models include a generated print_filter.prt listing the gauge-assigned channels, which is what makes large-basin calibration output tractable.
NetCDF output (cdfout = y)
The third flag on the print.prt output-format line (csvout / use_obj_lbls / cdfout). With cdfout = y the engine writes NetCDF-4 (classic-model) files instead of the corresponding text outputs, one file per enabled object × period: hru_wb_day.nc, channel_sd_day.nc, basin_wb_aa.nc, and so on.
| Item | Value |
|---|---|
| Dimensions | time (unlimited) × obj (HRUs / channels / 1 for basin; filtered channel count when print_filter.prt is active) |
| Coordinate variables | time (days since <start-year>-01-01), mo, day_mo, yrc, jday; obj_id, gis_id per object |
| Data variables | Named columns for hru_wb-family streams; generic v1..vN for the rest (channel_sd_day: flow output is v41) |
| Fill / conventions | Fill value -9999; CF-1.10; global attrs title, model="SWAT+" |
| SWATPLUS_NC_DEFLATE | Env var, first digit clamped 0–9; default compression level 4; production sets 0 |
| Suppressed text streams | With cdfout=y the engine forces mgtout, crop_yld, hydcon, fdcout (and several period flags without NetCDF writers) to n — otherwise those writers would hit never-opened units |