Removed division by zero in speed benchmarks

If some library is so fast that it goes below the resolution of the
timer we're using to measure it, the measured duration may be zero, and
then trigger a division by zero when we convert it to a speed in Hz.

This could possibly happen with a very fast library (Libsodium), on a
very fast machine, with a sufficiently low resolution timer.

This patch reworks and simplifies things a bit, and adds an explicit
check. We now print "too fast to be measured" instead of dividing by
zero.

diff --git a/tests/speed-sodium.c b/tests/speed-sodium.c
index a1c50abeeb977936162c7f783908242b41cbdfc2..5ad35bdba1722520429b7225c3acf377aa66d307 100644 (file)
--- a/tests/speed-sodium.c
+++ b/tests/speed-sodium.c
@@ -126,12 +126,12 @@ static u64 edDSA_check(void)
 int main()
 {
     SODIUM_INIT;
-    print("Chacha20         ",chacha20()     /DIV,"megabytes  per second");
-    print("Poly1305         ",poly1305()     /DIV,"megabytes  per second");
-    print("Auth'd encryption",authenticated()/DIV,"megabytes  per second");
-    print("Blake2b          ",blake2b()      /DIV,"megabytes  per second");
-    print("Sha512           ",sha512()       /DIV,"megabytes  per second");
-    print("Argon2i, 3 passes",argon2i()      /DIV,"megabytes  per second");
+    print("Chacha20         ",chacha20()     *MUL,"megabytes  per second");
+    print("Poly1305         ",poly1305()     *MUL,"megabytes  per second");
+    print("Auth'd encryption",authenticated()*MUL,"megabytes  per second");
+    print("Blake2b          ",blake2b()      *MUL,"megabytes  per second");
+    print("Sha512           ",sha512()       *MUL,"megabytes  per second");
+    print("Argon2i, 3 passes",argon2i()      *MUL,"megabytes  per second");
     print("x25519           ",x25519()           ,"exchanges  per second");
     print("EdDSA(sign)      ",edDSA_sign()       ,"signatures per second");
     print("EdDSA(check)     ",edDSA_check()      ,"checks     per second");

diff --git a/tests/speed-tweetnacl.c b/tests/speed-tweetnacl.c
index 5607ad11fe29a6c7462ca934cb0e541995a1684d..00a1f9e5f7bbcb6dc6e6b8430d86de2e8a496c7c 100644 (file)
--- a/tests/speed-tweetnacl.c
+++ b/tests/speed-tweetnacl.c
@@ -102,10 +102,10 @@ static u64 edDSA_check(void)
 
 int main()
 {
-    print("Salsa20          ",salsa20()      /DIV,"megabytes  per second");
-    print("Poly1305         ",poly1305()     /DIV,"megabytes  per second");
-    print("Auth'd encryption",authenticated()/DIV,"megabytes  per second");
-    print("Sha512           ",sha512()       /DIV,"megabytes  per second");
+    print("Salsa20          ",salsa20()      *MUL,"megabytes  per second");
+    print("Poly1305         ",poly1305()     *MUL,"megabytes  per second");
+    print("Auth'd encryption",authenticated()*MUL,"megabytes  per second");
+    print("Sha512           ",sha512()       *MUL,"megabytes  per second");
     print("x25519           ",x25519()           ,"exchanges  per second");
     print("EdDSA(sign)      ",edDSA_sign()       ,"signatures per second");
     print("EdDSA(check)     ",edDSA_check()      ,"checks     per second");

diff --git a/tests/speed.c b/tests/speed.c
index 7cb10563bb6ed68efbd70eedebaa5e16c9b167c1..fbdf7d0d1f56e50e161c71559c6630a0eb2377c5 100644 (file)
--- a/tests/speed.c
+++ b/tests/speed.c
@@ -128,12 +128,12 @@ static u64 edDSA_check(void)
 
 int main()
 {
-    print("Chacha20         ",chacha20()     /DIV,"megabytes  per second");
-    print("Poly1305         ",poly1305()     /DIV,"megabytes  per second");
-    print("Auth'd encryption",authenticated()/DIV,"megabytes  per second");
-    print("Blake2b          ",blake2b()      /DIV,"megabytes  per second");
-    print("Sha512           ",sha512()       /DIV,"megabytes  per second");
-    print("Argon2i, 3 passes",argon2i()      /DIV,"megabytes  per second");
+    print("Chacha20         ",chacha20()     *MUL,"megabytes  per second");
+    print("Poly1305         ",poly1305()     *MUL,"megabytes  per second");
+    print("Auth'd encryption",authenticated()*MUL,"megabytes  per second");
+    print("Blake2b          ",blake2b()      *MUL,"megabytes  per second");
+    print("Sha512           ",sha512()       *MUL,"megabytes  per second");
+    print("Argon2i, 3 passes",argon2i()      *MUL,"megabytes  per second");
     print("x25519           ",x25519()           ,"exchanges  per second");
     print("EdDSA(sign)      ",edDSA_sign()       ,"signatures per second");
     print("EdDSA(check)     ",edDSA_check()      ,"checks     per second");

diff --git a/tests/speed.h b/tests/speed.h
index 5f472211fa989f834dcc69a0bccd5bd30aa7f157..c83b001594328dafc7085020e733cd520d0a077c 100644 (file)
--- a/tests/speed.h
+++ b/tests/speed.h
@@ -10,38 +10,30 @@ typedef struct timespec timespec;
 #define KILOBYTE 1024
 #define MEGABYTE 1024 * KILOBYTE
 #define SIZE     (256 * KILOBYTE)
-#define DIV      (MEGABYTE / SIZE)
+#define MUL      (MEGABYTE / SIZE)
+#define BILLION  1000000000
 
-static timespec diff(timespec start, timespec end)
+// Difference in nanoseconds
+static u64 diff(timespec start, timespec end)
 {
-    timespec duration;
-    duration.tv_sec  = end.tv_sec  - start.tv_sec;
-    duration.tv_nsec = end.tv_nsec - start.tv_nsec;
-    if (duration.tv_nsec < 0) {
-        duration.tv_nsec += 1000000000;
-        duration.tv_sec  -= 1;
-    }
-    return duration;
-}
-
-static timespec min(timespec a, timespec b)
-{
-    if (a.tv_sec < b.tv_sec ||
-        (a.tv_sec == b.tv_sec && a.tv_nsec < b.tv_nsec)) {
-        return a;
-    }
-    return b;
+    return
+        (end.tv_sec  - start.tv_sec ) * BILLION +
+        (end.tv_nsec - start.tv_nsec);
 }
 
-static u64 speed(timespec duration)
+static u64 min(u64 a, u64 b)
 {
-    static const u64 giga = 1000000000;
-    return giga / (duration.tv_nsec + duration.tv_sec * giga);
+    return a < b ? a : b;
 }
 
-static void print(const char *name, u64 speed, const char *unit)
+static void print(const char *name, u64 duration, const char *unit)
 {
-    printf("%s: %5" PRIu64 " %s\n", name, speed, unit);
+    if (duration == 0) {
+        printf("%s: too fast to be measured\n", name);
+    } else {
+        u64 speed_hz = BILLION / duration;
+        printf("%s: %5" PRIu64 " %s\n", name, speed_hz, unit);
+    }
 }
 
 #define TIMESTAMP(t)                            \
@@ -49,11 +41,7 @@ static void print(const char *name, u64 speed, const char *unit)
     clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &t)
 
 #define TIMING_START                            \
-    timespec duration;                          \
-    duration.tv_sec = -1;                       \
-    duration.tv_nsec = -1;                      \
-    duration.tv_sec  = 3600 * 24;               \
-    duration.tv_nsec = 0;                       \
+    u64 duration = -1u;                         \
     FOR (i, 0, 500) {                           \
         TIMESTAMP(start);
 
@@ -61,4 +49,4 @@ static void print(const char *name, u64 speed, const char *unit)
     TIMESTAMP(end);                             \
     duration = min(duration, diff(start, end)); \
     } /* end FOR*/                              \
-    return speed(duration)
+    return duration