On 28/06/2021 9:56 am, Andrew Rowley wrote:
On 26/06/2021 4:50 pm, David Crayford wrote:
That's an exaggeration. C is just over 3x faster.
C
mckoss-c830;14285;5.0;1;algorithm=wheel,faithful=yes,bits=1
The C implementations are confusing because there are various
algorithm changes as well, rather than just the language change. This
one uses the wheel algorithm instead of the base (original). I don't
know enough math or algorithms to say what difference that makes.
I think the solution_2/sieve_1of2.c is the one that corresponds to the
C++ code.
That not particularily fast either. How can Python be faster than C?
danielspaangberg_1of2;2756;5.000862;1;algorithm=base,faithful=yes,bits=1
BTW, if you want to compile any of the programs in solution_2 you will
need the following header file as clock_gettime() and gettimeofday() are
not implemented on z/OS.
#ifndef TIME_ZOS_H
#define TIME_ZOS_H 1
#include <stdint.h>
#include <errno.h>
#define clock_gettime(n,ts) gettimeofdayMonotonic(ts)
static inline int gettimeofdayMonotonic(struct timespec* Output) {
// The POSIX gettimeofday() function is not available on z/OS. Therefore,
// we will call stcke and other hardware instructions in implement
equivalent.
// Note that nanoseconds alone will overflow when reaching new epoch
in 2042.
struct _t {
uint64_t Hi;
uint64_t Lo;
};
struct _t Value = {0, 0};
uint64_t CC = 0;
asm(" stcke %0\n"
" ipm %1\n"
" srlg %1,%1,28\n"
: "=m"(Value), "+r"(CC)::);
if (CC != 0) {
errno = EMVSTODNOTSET;
return CC;
}
uint64_t us = (Value.Hi >> 4);
uint64_t ns = ((Value.Hi & 0x0F) << 8) + (Value.Lo >> 56);
ns = (ns * 1000) >> 12;
us = us - 2208988800000000;
register uint64_t DivPair0 asm("r0"); // dividend (upper half), remainder
DivPair0 = 0;
register uint64_t DivPair1 asm("r1"); // dividend (lower half), quotient
DivPair1 = us;
uint64_t Divisor = 1000000;
asm(" dlgr %0,%2" : "+r"(DivPair0), "+r"(DivPair1) : "r"(Divisor) :);
Output->tv_sec = DivPair1;
Output->tv_nsec = DivPair0 * 1000 + ns;
return 0;
}
#endif
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