Added multi-pass approach to fixtest, now produces more accurate results. On x86 with an FPU and full optimization fixed point is about 20% slower than floating point.

The multi-pass approach means that this test should run unmodified on embedded environments due to lower memory usage, this test also more realistically tests for cache behaviour.

2 files changed, 37 insertions, 31 deletions

diff --git a/fixtest/fixtest.depend b/fixtest/fixtest.depend
index ac2f94a..db7e8ce 100644
--- a/fixtest/fixtest.depend
+++ b/fixtest/fixtest.depend
@@ -1,5 +1,5 @@
 # depslib dependency file v1.0

-1298566464 source:g:\vrfx\libfixmath\fixtest\main.c

+1298567472 source:g:\vrfx\libfixmath\fixtest\main.c

 	<stdio.h>

 	<stdlib.h>

 	<math.h>

diff --git a/fixtest/main.c b/fixtest/main.c
index 86a2c23..a7e9e89 100644
--- a/fixtest/main.c
+++ b/fixtest/main.c
@@ -14,47 +14,53 @@ int main(int argc, char** argv) {
 

     hiclock_init();

 

-	uintptr_t iter = (1 << 16);

+	uintptr_t args = (1 <<  8);

+	uintptr_t iter = (1 <<  8);

 	uintptr_t pass = (1 <<  8);

 

 	uintptr_t i;

 	srand(time(NULL));

 

-	fix16_t fix_args[iter];

-	for(i = 0; i < iter; i++)

-		fix_args[i] = (rand() ^ (rand() << 16));

-	fix16_t fix_result[iter];

-	hiclock_t fix_start = hiclock();

-	for(i = 0; i < pass; i++) {

-		uintptr_t j;

-		for(j = 0; j < iter; j++)

-			fix_result[j] = fix16_atan(fix_args[j]);

-	}

-	hiclock_t fix_end = hiclock();

-

-	float   flt_args[iter];

-	for(i = 0; i < iter; i++)

-		flt_args[i] = fix16_to_float(fix_args[i]);

-	float   flt_result[iter];

-	hiclock_t flt_start = hiclock();

-	for(i = 0; i < pass; i++) {

-		uintptr_t j;

-		for(j = 0; j < iter; j++)

-			flt_result[j] = atanf(flt_args[j]);

-	}

-	hiclock_t flt_end = hiclock();

+	hiclock_t fix_duration = 0;

+	hiclock_t flt_duration = 0;

+	fix16_t   fix_error = 0;

 

-	fix16_t fix_error = 0;

-	for(i = 0; i < iter; i++)

-		fix_error += abs(fix16_from_float(flt_result[i]) - fix_result[i]);

+	uintptr_t k;

+	for(k = 0; k < pass; k++) {

+		fix16_t fix_args[args];

+		for(i = 0; i < args; i++)

+			fix_args[i] = (rand() ^ (rand() << 16));

+		fix16_t fix_result[args];

+		hiclock_t fix_start = hiclock();

+		for(i = 0; i < iter; i++) {

+			uintptr_t j;

+			for(j = 0; j < args; j++)

+				fix_result[j] = fix16_atan(fix_args[j]);

+		}

+		hiclock_t fix_end = hiclock();

 

-	hiclock_t flt_duration = (flt_end - flt_start);

-	hiclock_t fix_duration = (fix_end - fix_start);

+		float   flt_args[args];

+		for(i = 0; i < args; i++)

+			flt_args[i] = fix16_to_float(fix_args[i]);

+		float   flt_result[args];

+		hiclock_t flt_start = hiclock();

+		for(i = 0; i < iter; i++) {

+			uintptr_t j;

+			for(j = 0; j < args; j++)

+				flt_result[j] = atanf(flt_args[j]);

+		}

+		hiclock_t flt_end = hiclock();

+

+		for(i = 0; i < args; i++)

+			fix_error += abs(fix16_from_float(flt_result[i]) - fix_result[i]);

+		flt_duration += (flt_end - flt_start);

+		fix_duration += (fix_end - fix_start);

+	}

 

 	printf("Floating Point: %08"PRIuHICLOCK" @ %"PRIu32"Hz\n", flt_duration, HICLOCKS_PER_SEC);

 	printf("Fixed Point:    %08"PRIuHICLOCK" @ %"PRIu32"Hz\n", fix_duration, HICLOCKS_PER_SEC);

 	printf("Difference:     %08"PRIiHICLOCK" (% 3.2f%%)\n", (flt_duration - fix_duration), ((fix_duration * 100.0) / flt_duration));

-	printf("Error:          %f%%\n", ((fix16_to_dbl(fix_error) * 100.0) / iter));

+	printf("Error:          %f%%\n", ((fix16_to_dbl(fix_error) * 100.0) / (args * pass)));

 

     return EXIT_SUCCESS;

 }