star-hitran

commit 6ed4f0c790fa295897ff53ec7ae684e84602d373
parent 372d23022f0eb854716e8abf9aaa182ab5ecf9e6
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Mon, 12 Jan 2026 16:50:39 +0100

shtr: measures line access performance

Add the -a option, which activates the linear/random line access test
bench. As expected, decompression dominates access time, and random
access is three orders of magnitude slower than linear access.

Diffstat:
M
doc/shtr.1
 | 
7
+++++--
M
src/shtr_main.c
 | 
45
++++++++++++++++++++++++++++++++++++++++++---

2 files changed, 47 insertions(+), 5 deletions(-)
diff --git a/doc/shtr.1 b/doc/shtr.1
@@ -15,7 +15,7 @@
 .\"
 .\" You should have received a copy of the GNU General Public License
 .\" along with this program. If not, see <http://www.gnu.org/licenses/>.
-.Dd January 9, 2026
+.Dd January 12, 2026
 .Dt SHTR 1
 .Os
 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
@@ -25,7 +25,7 @@
 .\""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
 .Sh SYNOPSIS
 .Nm
-.Op Fl hsv
+.Op Fl ahsv
 .Op Fl l Ar lines
 .Op Fl m Ar molparam
 .Op Fl o Ar output
@@ -75,6 +75,9 @@ The total memory used is finally printed.
 .Pp
 The options are as follows:
 .Bl -tag -width Ds
+.It Fl a
+Measure line access performance.
+Both linear and random access are tested.
 .It Fl h
 Use suffixes to make memory usage easier to read: the number of
 consecutive digits is then three or less, using powers of 2 for sizes
diff --git a/src/shtr_main.c b/src/shtr_main.c
@@ -20,6 +20,7 @@
 
 #include "shtr.h"
 
+#include <rsys/clock_time.h>
 #include <rsys/cstr.h>
 #include <rsys/mem_allocator.h>
 #include <rsys/rsys.h>
@@ -35,13 +36,14 @@ struct args {
   char* lines;
   char* output;
 
+  int bench_line_access;
   int internal_format;
   int verbose; /* Verbosity level */
   int compression; /* Compression level */
   int human_readable;
 };
 static const struct args ARGS_DEFAULT = {
-  NULL, NULL, NULL, 0, 0, SHTR_DEFAULT_COMPRESSION, 0
+  NULL, NULL, NULL, 0, 0, 0, SHTR_DEFAULT_COMPRESSION, 0
 };
 
 struct cmd {
@@ -59,7 +61,7 @@ static INLINE void
 usage(FILE* stream)
 {
   fprintf(stream,
-"usage: shtr [-hsv] [-l lines] [-m molparam] [-o output] [-z compression_level]\n");
+"usage: shtr [-ahsv] [-l lines] [-m molparam] [-o output] [-z compression_level]\n");
 }
 
 static res_T
@@ -72,8 +74,9 @@ args_init(struct args* args, int argc, char** argv)
 
   *args = ARGS_DEFAULT;
 
-  while((opt = getopt(argc, argv, "hl:m:o:svz:")) != -1) {
+  while((opt = getopt(argc, argv, "ahl:m:o:svz:")) != -1) {
     switch(opt) {
+      case 'a': args->bench_line_access = 1; break;
       case 'h': args->human_readable = 1; break;
       case 'l': args->lines = optarg; break;
       case 'm': args->molparam = optarg; break;
@@ -250,6 +253,41 @@ error:
   goto exit;
 }
 
+static void
+bench_line_access(struct shtr_line_list* lines)
+{
+  struct shtr_line line;
+  struct time t0, t1;
+  const size_t random_read_count = 10000;
+  double lines_per_second = 0;
+  int64_t usec = 0;
+  size_t i, n;
+
+  ASSERT(lines);
+
+  SHTR(line_list_get_size(lines, &n));
+
+  /* Linear access */
+  time_current(&t0);
+  FOR_EACH(i, 0, n) {
+    SHTR(line_list_at(lines, i, &line));
+  }
+  usec = time_val(time_sub(&t0, time_current(&t1), &t0), TIME_USEC);
+  lines_per_second = 1.e9 * (double)n / (double)usec;
+  printf("linear access: %g lines per second\n", lines_per_second);
+
+  /* Random access */
+  time_current(&t0);
+  FOR_EACH(i, 0, random_read_count) {
+    const double r = (double)rand() / (double)(RAND_MAX-1);
+    const size_t iline = (size_t)(r * (double)n);
+    SHTR(line_list_at(lines, iline, &line));
+  }
+  usec = time_val(time_sub(&t0, time_current(&t1), &t0), TIME_USEC);
+  lines_per_second = 1.e9 * (double)random_read_count / (double)usec;
+  printf("random access: %g lines per second\n", lines_per_second);
+}
+
 static res_T
 cmd_run(const struct cmd* cmd)
 {
@@ -266,6 +304,7 @@ cmd_run(const struct cmd* cmd)
   if(cmd->args.lines) {
     if((res = load_lines(cmd, &lines)) != RES_OK) goto error;
     if((res = process_lines(cmd, lines)) != RES_OK) goto error;
+    if(cmd->args.bench_line_access) bench_line_access(lines);
   }
 
   sz = MEM_ALLOCATED_SIZE(&cmd->allocator);