Merge branch 'stclib:master' into modifiedHEADmodified

1 files changed, 37 insertions, 60 deletions

diff --git a/misc/benchmarks/various/cspan_bench.c b/misc/benchmarks/various/cspan_bench.c
index 589df13a..bfc0ead3 100644
--- a/misc/benchmarks/various/cspan_bench.c
+++ b/misc/benchmarks/various/cspan_bench.c
@@ -1,4 +1,5 @@
-#define STC_NDEBUG
+// ref: https://stackoverflow.com/questions/74382366/why-is-iterating-over-stdrangesviewsjoin-so-slow
+#define NDEBUG
 #include <stc/cspan.h>
 #include <stdio.h>
 #include <time.h>
@@ -11,9 +12,9 @@ enum {
     ny = 64,
     nz = 64
 };
+// subspan 15x5x10:
 int lx = 15, ly = 10, lz = 5;
-int hx = 20, hy = 15, hz = 15;
-intptr_t n = 1000000;
+int hx = 30, hy = 15, hz = 15;
 
 // define the contents of two nx x ny x nz arrays in and out
 double Vout[nx * ny * nz];
@@ -21,36 +22,15 @@ double Vin[nx * ny * nz]; //, 1.23;
 
 // define some slice indices for each dimension
 
-static void MDRanges_setup(intptr_t state)
-{
-    double sum = 0;
-    clock_t t = clock();
-
-    for (intptr_t s = 0; s < state; ++s)
-    {
-        MD3 r_in = cspan_md(Vin, nx, ny, nz);
-        MD3 r_out = cspan_md(Vout, nx, ny, nz);
-
-        r_in = cspan_slice(MD3, &r_in, {lx, hx}, {ly, hy}, {lz, hz});
-        r_out = cspan_slice(MD3, &r_out, {lx, hx}, {ly, hy}, {lz, hz});
-        MD3_iter i = MD3_begin(&r_in); // can be iterated "flat".
-        MD3_iter o = MD3_begin(&r_out);
-        sum += Vin[s % nx];
-    }
-    t = clock() - t;
-    printf("setup: %.1f ms, %f\n", 1000.0f * t / CLOCKS_PER_SEC, sum);
-}
-
-static void TraditionalForLoop(intptr_t state)
+static void Traditional_for_loop(intptr_t n)
 {
     clock_t t = clock();
     double sum = 0;
 
-    for (int s = 0; s < state; ++s) {
+    for (int s = 0; s < n; ++s) {
         for (int x = lx; x < hx; ++x) {
             for (int y = ly; y < hy; ++y) {
-                for (int z = lz; z < hz; ++z)
-                {
+                for (int z = lz; z < hz; ++z) {
                     double d = Vin[nz*(ny*x + y) + z];
                     Vout[nz*(ny*x + y) + z] += d;
                     sum += d;
@@ -59,68 +39,65 @@ static void TraditionalForLoop(intptr_t state)
         }
     }
     t = clock() - t;
-    printf("forloop: %.1f ms, %f\n", 1000.0f * t / CLOCKS_PER_SEC, sum);
+    printf("forloop : %.1f ms, %f\n", 1000.0f*t / CLOCKS_PER_SEC, sum);
 }
 
-static void MDRanges_nested_loop(intptr_t state)
+static void MDRanges_loop_over_joined(intptr_t n)
 {
+    clock_t t = clock();
     MD3 r_in = cspan_md(Vin, nx, ny, nz);
     MD3 r_out = cspan_md(Vout, nx, ny, nz);
     r_in = cspan_slice(MD3, &r_in, {lx, hx}, {ly, hy}, {lz, hz});
     r_out = cspan_slice(MD3, &r_out, {lx, hx}, {ly, hy}, {lz, hz});
-
-    // C++23: for (auto [o, i] : std::views::zip(flat(r_out), flat(r_in))) { o = i; }
-    clock_t t = clock();
     double sum = 0;
 
-    for (intptr_t s = 0; s < state; ++s) {
-        for (int x = 0; x < r_in.shape[0]; ++x) {
-            for (int y = 0; y < r_in.shape[1]; ++y) {
-                for (int z = 0; z < r_in.shape[2]; ++z)
-                {
-                    double d = *cspan_at(&r_in, x, y, z);
-                    *cspan_at(&r_out, x, y, z) += d;
-                    sum += d;
-                }
-            }
+    for (intptr_t s = 0; s < n; ++s) {
+        MD3_iter i = MD3_begin(&r_in);
+        MD3_iter o = MD3_begin(&r_out);
+
+        for (; i.ref; MD3_next(&i), MD3_next(&o))
+        {
+            *o.ref += *i.ref;
+            sum += *i.ref;
         }
     }
     t = clock() - t;
-    printf("nested: %.1f ms, %f\n", 1000.0f * t / CLOCKS_PER_SEC, sum);
+    printf("joined  : %.1f ms, %f\n", 1000.0f*t / CLOCKS_PER_SEC, sum);
 }
 
-static void MDRanges_loop_over_joined(intptr_t state)
+static void MDRanges_nested_loop(intptr_t n)
 {
+    clock_t t = clock();
     MD3 r_in = cspan_md(Vin, nx, ny, nz);
     MD3 r_out = cspan_md(Vout, nx, ny, nz);
     r_in = cspan_slice(MD3, &r_in, {lx, hx}, {ly, hy}, {lz, hz});
     r_out = cspan_slice(MD3, &r_out, {lx, hx}, {ly, hy}, {lz, hz});
-
-    // C++23: for (auto [o, i] : std::views::zip(flat(r_out), flat(r_in))) { o = i; }
     double sum = 0;
-    clock_t t = clock();
-
-    for (intptr_t s = 0; s < state; ++s) {
-        MD3_iter i = MD3_begin(&r_in);
-        MD3_iter o = MD3_begin(&r_out);
 
-        for (; i.ref; MD3_next(&i), MD3_next(&o))
-        {
-            *o.ref += *i.ref;
-            sum += *i.ref;
+    for (intptr_t s = 0; s < n; ++s) {
+        for (int x = 0; x < r_in.shape[0]; ++x) {
+            for (int y = 0; y < r_in.shape[1]; ++y) {
+                for (int z = 0; z < r_in.shape[2]; ++z)
+                {
+                    double d = *cspan_at(&r_in, x,y,z);
+                    *cspan_at(&r_out, x,y,z) += d;
+                    sum += d;
+                }
+            }
         }
     }
     t = clock() - t;
-    printf("joined: %.1f ms, %f\n", 1000.0f * t / CLOCKS_PER_SEC, sum);
+    printf("nested  : %.1f ms, %f\n", 1000.0f*t / CLOCKS_PER_SEC, sum);
 }
 
-int main()
+
+int main(void)
 {
+    intptr_t n = 100000;
     for (int i = 0; i < nx * ny * nz; ++i)
         Vin[i] = i + 1.23;
 
-    MDRanges_setup(n);
-    TraditionalForLoop(n);
-    MDRanges_nested_loop(n);
+    Traditional_for_loop(n);
     MDRanges_loop_over_joined(n);
+    MDRanges_nested_loop(n);
 }