diff options
Diffstat (limited to 'stdlib/random.c')
| -rw-r--r-- | stdlib/random.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/stdlib/random.c b/stdlib/random.c index ffa658d..370a610 100644 --- a/stdlib/random.c +++ b/stdlib/random.c @@ -35,16 +35,16 @@ then initialized to contain information for random number generation with that much state information. Good sizes for the amount of state information are 32, 64, 128, and 256 bytes. The state can be switched by - calling the setstate() function with the same array as was initiallized + calling the setstate() function with the same array as was initialized with initstate(). By default, the package runs with 128 bytes of state information and generates far better random numbers than a linear congruential generator. If the amount of state information is less than 32 bytes, a simple linear congruential R.N.G. is used. Internally, the - state information is treated as an array of longs; the zeroeth element of + state information is treated as an array of longs; the zeroth element of the array is the type of R.N.G. being used (small integer); the remainder of the array is the state information for the R.N.G. Thus, 32 bytes of state information will give 7 longs worth of state information, which will - allow a degree seven polynomial. (Note: The zeroeth word of state + allow a degree seven polynomial. (Note: The zeroth word of state information also has some other information stored in it; see setstate for details). The random number generation technique is a linear feedback shift register approach, employing trinomials (since there are fewer terms @@ -64,7 +64,7 @@ /* For each of the currently supported random number generators, we have a - break value on the amount of state information (you need at least thi + break value on the amount of state information (you need at least this many bytes of state info to support this random number generator), a degree for the polynomial (actually a trinomial) that the R.N.G. is based on, and separation between the two lower order coefficients of the trinomial. */ @@ -110,7 +110,7 @@ initstate(1, randtbl, 128); Note that this initialization takes advantage of the fact that srandom advances the front and rear pointers 10*rand_deg times, and hence the - rear pointer which starts at 0 will also end up at zero; thus the zeroeth + rear pointer which starts at 0 will also end up at zero; thus the zeroth element of the state information, which contains info about the current position of the rear pointer is just (MAX_TYPES * (rptr - state)) + TYPE_3 == TYPE_3. */ @@ -148,7 +148,7 @@ static struct random_data unsafe_state = the type of the current generator, the degree of the current polynomial being used, and the separation between the two pointers. Note that for efficiency of random, we remember the first location of - the state information, not the zeroeth. Hence it is valid to access + the state information, not the zeroth. Hence it is valid to access state[-1], which is used to store the type of the R.N.G. Also, we remember the last location, since this is more efficient than indexing every time to find the address of the last element to see if @@ -224,7 +224,7 @@ weak_alias (__initstate, initstate) Note: It is important that we also remember the locations of the pointers in the current state information, and restore the locations of the pointers from the old state information. This is done by multiplexing the pointer - location into the zeroeth word of the state information. Note that due + location into the zeroth word of the state information. Note that due to the order in which things are done, it is OK to call setstate with the same state as the current state Returns a pointer to the old state information. */ @@ -250,7 +250,7 @@ weak_alias (__setstate, setstate) /* If we are using the trivial TYPE_0 R.N.G., just do the old linear congruential bit. Otherwise, we do our fancy trinomial stuff, which is the - same in all ther other cases due to all the global variables that have been + same in all the other cases due to all the global variables that have been set up. The basic operation is to add the number at the rear pointer into the one at the front pointer. Then both pointers are advanced to the next location cyclically in the table. The value returned is the sum generated, |