There is an MCA parameter for this, but it's better to increase the default value, as 256M/(2K*2K*sizeof(double)) = 8 which is a little small. https://github.com/ICLDisco/parsec/blob/a9ab33d8287578c68c0349662352f280bc83e2c0/parsec/arena.c#L56C8-L56C38